Cold radiators in loft

[milleniumaire]

Hi, I've have a problem with my CH system for around 18 months now and it's time to get it sorted. Here's a diagram showing our current heating system:

The house is 21 years old and the loft extension was performed around 15 years ago. As you can see they simply extended the existing 15mm pipes up into the loft and then split them. The Vaillant equipment is 8 years old and still going well. We had the UFH installed 5 years ago as part of a kitchen extension.

Only one of the radiators in the loft gets a little warm, never hot and the other radiator and towel rail are always cold, so there's clearly a blockage or two. I have accessed the 15mm flow and return pipes to the loft at the point they are connected under the bathroom floor and the flow pipe gets very hot, the return pipe is barely warm. I have tried closing all valves to force the water into the loft pipes but it makes no difference.

I have been considering replacing the existing 15mm pipes into the loft with 22m pipes and connect them up earlier as is shown in the following diagram:

Obviously I'll have to resolve the existing blockages in the loft pipework.

My diagram may not be accurate for the Ground floor radiators. It currently shows the flow going into the final toilet radiator and then back out into the return. Is this how you would expect the pipes to be connected at the end of a run or would the flow become the return? The 1st Floor to loft connections shown in the first diagram are exactly as they are plumbed. So, if all the loft radiators were turned off, there's no way for the flow to return to the boiler (I think!). In fact, in my diagram the only way for the flow to become the return is through a radiator. Not sure how accurate this is.

A couple of concerns:
1. Will the boiler pump be able to handle the additional 22mm pipes running into the loft?
2. Should I consider re-routing (new) pipes around the loft as the "star" connection currently used looks to be a limitation to my untrained eye.

Thanks in advance for your thoughts.

 

[centralheatking]

Great diagrams well done. 15mm pipe is as you suspect the limitation. Putting in 22mm
will put less strain on the pump. Yes pipe up the loft with conventional flow and return.
centralheatking

 

[Gasmk1]

Have you actually bled the rads could be as simple as air or an air lock

 

[Stigster]

No matter what you shut off, every rad has a flow and return path to boiler.

Undersized pipework is an issue but you'd still expect them to all heat up fairly evenly if not as hot as they should. It does sound like a possible airlock as Gasmk1 says.
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Another thought, I know you have tried closing all the other rads down to force out any airlocks. However when that fails to work I would temporarily increase the system pressure to 2 or 2.5 bar which will compress down any slugs of air in the system and give the pump a better chance at moving air to a radiator where it can be bled off.

Return to normal operating pressure after trying that of course.

 

[milleniumaire]

Have you actually bled the rads could be as simple as air or an air lock

No matter what you shut off, every rad has a flow and return path to boiler.

Undersized pipework is an issue but you'd still expect them to all heat up fairly evenly if not as hot as they should. It does sound like a possible airlock as Gasmk1 says.

Hi guys, thanks for responding.

When I first encountered the issue I assumed it was the TRV's that were sticking on the two radiators and so replaced them. While doing this I removed both radiators and gave them a good flush through outside. There was a fair amount of black gunge in them, despite having a magnacelan on the system (oops, forgot to include that in my diagrams ).

Unfortunately, this didn't make any difference. My suspicion is the water flow in these radiators is so poor due to the 15mm pipes connected to the very end of the pipe run and the "star" method of connecting them up, that gunge has collected in the pipes feeding the radiators.

If it was simply air, couldn't that be flushed through by closing off every other radiator to increase the flow/pressure? I have tried this a couple of times.

Great diagrams well done. 15mm pipe is as you suspect the limitation. Putting in 22mm
will put less strain on the pump. Yes pipe up the loft with conventional flow and return.
centralheatking

Thanks for posting. It's strange as I imagined a larger 22mm pipe would put more strain on the pump as it has a larger volume of water to move through the pipe, especially as this new run of 22mm has to go from one end of the house to the other, then up a floor.

 

[Stigster]

If it was simply air, couldn't that be flushed through by closing off every other radiator to increase the flow/pressure? I have tried this a couple of times.

Sometimes the slug of air is too long and compressible to be moved by the pump even under ideal circumstances with the other rads closed. That's why I suggested trying with the pressure increased. It compresses the trapped bubble giving the pump a better chance to move it to a rad.

I only suggest it because it sometimes works and is easy enough to do. Always try the simpler things first, which I appreciate you have been doing but that's one more to try.

 

[milleniumaire]

Another thought, I know you have tried closing all the other rads down to force out any airlocks. However when that fails to work I would temporarily increase the system pressure to 2 or 2.5 bar which will compress down any slugs of air in the system and give the pump a better chance at moving air to a radiator where it can be bled off.

Return to normal operating pressure after trying that of course.

Sorry Stigster I didn't see this original post. I will definitely try this. I assume to increase the system pressure it's simply a case of letting more water into the system and monitoring the pressure gauge. While the boiler is running hot, the pressure is at 1.8 bar, so I guess I could increase this to 2.5 bar and then afterwards let water out through the magnaclean connections.

 

[centralheatking]

Sometimes the slug of air is too long and compressible to be moved by the pump even under ideal circumstances with the other rads closed. That's why I suggested trying with the pressure increased. It compresses the trapped bubble giving the pump a better chance to move it to a rad.

I only suggest it because it sometimes works and is easy enough to do. Always try the simpler things first, which I appreciate you have been doing but that's one more to try.

You could shoot the system up with mains pressure ...find a rad with a good type mt cock
connect hose with a jubilee clip and put the other end on to outside tap. close off boiler
flow and return then shoot it up with mains pressure water, start at the bottom and bleed every rad going upwards and along so the last rad is highest and furtherest away.
In case anybody wants to do this with open vented it works but be carefull not to overfill
the F & E tank. blip the pump on and off ...its a bit like heart surgery for heating systems.
then undo the lot and maybe dump all the water and do again..its not rocket science
centralheatking

 

[milleniumaire]

You could shoot the system up with mains pressure ...find a rad with a good type mt cock
connect hose with a jubilee clip and put the other end on to outside tap. close off boiler
flow and return then shoot it up with mains pressure water, start at the bottom and bleed every rad going upwards and along so the last rad is highest and furtherest away.
In case anybody wants to do this with open vented it works but be carefull not to overfill
the F & E tank. blip the pump on and off ...its a bit like heart surgery for heating systems.
then undo the lot and maybe dump all the water and do again..its not rocket science
centralheatking

It's interesting you have mentioned using mains pressure as I've read about someone doing this to remove a blockage caused by sludge.

In my attempt to remove the blockage I was going to do the following:
1. Empty some water from the CH system, enough to empty the loft radiators and loft pipe work, but ideally still keep the bedroom radiators full. This will be a guessing game!
2. Disconnect the loft radiator piping from the two 15mm pipes currently feeding the loft from the bathroom and then connect these two pipes together. At this point I have isolated the loft radiators from the rest of the system.
3. Re-pressurise the system so that it can continue to be used in the rest of the house.

I then have 2 pipes going to each radiator in the loft and I can connect, in turn, each radiator circuit to a hose pipe as you have suggested. As it is the loft, I would need a long piece of hose (just bought a 30m hose) connected to the outside tap, so I'm a little unsure what pressure I could achieve given it is going up to the 2nd floor. The other side of the circuit I would connect to a hose that terminated in the loft toilet. I can then turn on the outside tap and see if any water flows into a toilet. For the cold towel rail and cold radiator I suspect nothing will flow through. For the warm radiator I may get a trickle.

I'm not sure what the mains water pressures involved would be in doing this but suspect it will still be higher than that produced by the CH system.

If this fails I was planning to access the piping under each radiator. I haven't mentioned before, but the 15mm feed and return pipes to the loft are copper (as is the rest of the house), however, the 15mm pipes to the loft radiators are all plastic (and yes I've checked they are the correct CH pipes given this was installed 15 years ago). My understanding of plastic piping is that the joints, especially elbows, can reduce the diameter of the pipe, so I suspect if there is a blockage it is likely to be on the elbows underneath each radiator, where the plastic pipe is connected to the copper tails going to the radiator valves. Of course this is all guesswork

 

[milleniumaire]

..... I did get a company round to quote for power flushing the system as I thought this might clear the loft radiators. However, they told me it wouldn't and therefore not to waste my money, which was very honest of them!
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...... Yes pipe up the loft with conventional flow and return.
centralheatking

So, the loft pipes would be run as follows?

Or, should the flow be connected to the return to ensure even when all loft radiator valves were closed, the flow would cycle back round to the boiler:

I confess, I haven't been able to find any CH diagrams that show this and maybe the "hot" water in the flow shouldn't be allowed to simply return to the boiler.

 

[centralheatking]

Yes of course set up a shoot up...in down below and find another outlet to make a curcuit
I usually put the output hose onto a hard surface ..road whatever ..so you can see what
ferric sludge comes out and when it goes clear. I have being doing this method for 20 + years
it cheap and works. basically the pump boys dont want you to know about this method
because of ££££££ it works . centralheatking

 

[centralheatking]

... I did get a company round to quote for power flushing the system as I thought this might clear the loft radiators. However, they told me it wouldn't and therefore not to waste my money, which was very honest of them!
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So, the loft pipes would be run as follows?

View attachment 40985

Or, should the flow be connected to the return to ensure even when all loft radiator valves were closed, the flow would cycle back round to the boiler:

View attachment 40986

I confess, I haven't been able to find any CH diagrams that show this and maybe the "hot" water in the flow shouldn't be allowed to simply return to the boiler.

Maybe too many rads on the middle floor set up if its on 15mm flow and rtn but in principle
its all dandy ...carry on ...chking

 

[milleniumaire]

Having done some Googling, I think my second diagram, showing the flow connected to the return, is essentially a bypass at the furthest end of the CH loft piping. From what I can gather this isn't required, or particularly good practice. Also, my ecoTEC 637 system boiler has a built in bypass valve.

So, assuming I connect up the loft radiators as shown in the first diagram, if ALL the loft radiators and towel rail are closed, the flow of hot water will simply "stop" in the loft, but will continue on the first and ground floor.

 

[EvilDrPorkChop]

I'd take the rads off first, put pieces of pipe between the valves. Turn all other radiators off, make sure the water and UFH is turned off, ensure all bypass valves are closed off and run it. If the pipework gets hot then you either need to repipe in 22mm or just get a bigger pump (Grunfos do a light commerical one which is brilliant) - the latter would be your easier option.

You have to remember the pump in the boiler is only designed to give 6 meter head too so might not be big enough for your system. You will also benefit putting the pump in 100% output mode on the computer on the Vaillant boiler. The internal bypass on the Vaillant might also not be set correctly (Read the MI) however you will have to get a GSR engineer in to alter that as it requires removing the front cover of the boiler.

If it doesn't get hot at all then you've got an issue with the pipes going to the loft. If they're done in plastic they could be kinked over somewhere under a floor etc...

 

[John.g]

Also, with a cold system, the expansion vessel pressure should be > 0.8/1 bar to overcome the static head of ~ 0.7 bar due to the loft location, also making sure that the pressure is changing with hot and cold conditions in case the gauge is blocked/faulty.

 

[Stu-B]

I would try bleeding the rads at the top of the system first, air is less dense that water so all the would collect up there.

 

[Stigster]

Having done some Googling, I think my second diagram, showing the flow connected to the return, is essentially a bypass at the furthest end of the CH loft piping. From what I can gather this isn't required, or particularly good practice. Also, my ecoTEC 637 system boiler has a built in bypass valve.

So, assuming I connect up the loft radiators as shown in the first diagram, if ALL the loft radiators and towel rail are closed, the flow of hot water will simply "stop" in the loft, but will continue on the first and ground floor.

That is correct. As you have worked out, if you close all the rads on the loft part of the system, the water will stop flowing through the main flow and return but only in that section. The rest flows perfectly fine and normal. Linking the flow and return will introduce a bypass, again as you have realised and this may stop the rads in the loft from working at all as the flow will take the path of least resistance and probably fail to flow through the rad at all or at least very poorly.

 

[ShaunCorbs]

have you tried turning all the other rads off via there trvs do the loft rads get warm / start to?

 

[Stigster]

have you tried turning all the other rads off via there trvs do the loft rads get warm / start to?

He mentioned that in his first post. Don't worry though, I asked the same question having missed where he said that too and had to edit my post.

 

[milleniumaire]

You have to remember the pump in the boiler is only designed to give 6 meter head too so might not be big enough for your system. You will also benefit putting the pump in 100% output mode on the computer on the Vaillant boiler. The internal bypass on the Vaillant might also not be set correctly (Read the MI) however you will have to get a 'Registered Professional Gas Engineer' engineer in to alter that as it requires removing the front cover of the boiler.

Thanks for the info. This is a little beyond my knowledge level, but I will consider it after I have tried everything else, if the issue persists.

In my case, it is actually easier for me to lay some new 22mm pipe as I'm currently renovating my bathroom, which involves lifting a lot of floor boards. This is the reason why I've decided to attempt to resolve the loft issue now, while I've got access to the bathroom CH pipes that feed the loft.

Our boiler is due a service next month, so I will discuss it with the heating engineer and see what he says, however, I hope to have the loft radiators working before then.

have you tried turning all the other rads off via there trvs do the loft rads get warm / start to?

Yes, I have tried this a couple of times and when the "power flushing guy" came round, he also tried it. I think he assumed he would easily be able to clear the blockage, but it made no difference.

I will try this again however but with the pressure raised to 2.5 bar as suggested by Stigster.

 

[ShaunCorbs]

Thanks for the info. This is a little beyond my knowledge level, but I will consider it after I have tried everything else, if the issue persists.

In my case, it is actually easier for me to lay some new 22mm pipe as I'm currently renovating my bathroom, which involves lifting a lot of floor boards. This is the reason why I've decided to attempt to resolve the loft issue now, while I've got access to the bathroom CH pipes that feed the loft.

Our boiler is due a service next month, so I will discuss it with the heating engineer and see what he says, however, I hope to have the loft radiators working before then.



Yes, I have tried this a couple of times and when the "power flushing guy" came round, he also tried it. I think he assumed he would easily be able to clear the blockage, but it made no difference.

I will try this again however but with the pressure raised to 2.5 bar as suggested by Stigster.

Pull one of the rads off

Open the flow into a bucket does much water come out and the pressure drop in the system

Do the same test on the return will tell you which one could be blocked

 

[milleniumaire]

Pull one of the rads off

Open the flow into a bucket does much water come out and the pressure drop in the system

Do the same test on the return will tell you which one could be blocked

Thanks Shaun. You have just reminded me that last year after I had replaced the TRV's on both radiators, I tried this. The water from the piping connected to the lockshield side of the radiator (I would assume the return pipe) was much slower, however, there was water coming out, which did confuse me as this suggested it wasn't blocked.

 

[ShaunCorbs]

Thanks Shaun. You have just reminded me that last year after I had replaced the TRV's on both radiators, I tried this. The water from the piping connected to the lockshield side of the radiator (I would assume the return pipe) was much slower, however, there was water coming out, which did confuse me as this suggested it wasn't blocked.

Might be draining from the other rads etc close them off then test

 

[milleniumaire]

Sorry Stigster I didn't see this original post. I will definitely try this. I assume to increase the system pressure it's simply a case of letting more water into the system and monitoring the pressure gauge. While the boiler is running hot, the pressure is at 1.8 bar, so I guess I could increase this to 2.5 bar and then afterwards let water out through the magnaclean connections.

Tried this tonight but increasing pressure didn't make any difference.

At the weekend I will drain the loft down and disconnect it from the rest of the heating system, then after removing the radiators try forcing mains pressure water through some of the pipes.

 

[milleniumaire]

I had another go at flushing through last night, but the water is still only trickling through, so the pipe run I'm currently working on is still obviously blocked. After I poured out the water from the bucket, I was surprised to see this:

This is from only one pipe run of the 6 I have to flush!

Although I've flushed through one of the radiators outside, I may replace them both as they are around 15 years old. Not sure what to do about the chrome towel rail. I assume these can also corrode on the inside?

Not sure if this sludge in the loft pipes is purely from the loft radiators or if it will be from the whole house, but will have settled in the loft pipes due to the poor flow.

This amount of sludge explains why the radiators in the loft aren't warming!

 

[centralheatking]

I had another go at flushing through last night, but the water is still only trickling through, so the pipe run I'm currently working on is still obviously blocked. After I poured out the water from the bucket, I was surprised to see this:

View attachment 41184

View attachment 41185

This is from only one pipe run of the 6 I have to flush!

Although I've flushed through one of the radiators outside, I may replace them both as they are around 15 years old. Not sure what to do about the chrome towel rail. I assume these can also corrode on the inside?

Not sure if this sludge in the loft pipes is purely from the loft radiators or if it will be from the whole house, but will have settled in the loft pipes due to the poor flow.

This amount of sludge explains why the radiators in the loft aren't warming!

Well done so far, it gets easier with practice, look on the bright side, at least the sludge is black...brown sludge is very naughty. Remember when you think its all done it is not
at least two more passes...but think how much money you are saving and you know its been done. award yourself 4 tins of whatever straight away and a similar portion at the end with a takeaway...centralheatking

 

[milleniumaire]

Well done so far, it gets easier with practice, look on the bright side, at least the sludge is black...brown sludge is very naughty.

I'm intrigued. What is brown sludge?

 

[milleniumaire]

One radiator and associated pipes have now been cleaned out and reconnected to the CH system and it is working perfectly.

Just the towel rail and another radiator to go.....

 

[centralheatking]

I'm intrigued. What is brown sludge?

Oh sorry I missed this, my understanding is thus
1. Black Ferric Sludge occurs with a sealed system inc. an open vented system and needs to be dealt with.
2. Brown Ferric Sludge indicates that the system is continually introducing fresh water with air dissolved into it, maybe eg an open vented system is pumping over.
I tested this towards the end of my last house which I sold for demolition...I had an Eclipse MicroMag industrial filter on it when we deliberately left an mt cock slightly open the ch water turned from black to brown when we took the micromag out of circuit.
To explain my main workshop in that house had the boiler located there so we used to use it as a test vehicle for all sorts of things.
centralheatking

 

[milleniumaire]

2. Brown Ferric Sludge indicates that the system is continually introducing fresh water with air dissolved into it, maybe eg an open vented system is pumping over.

I did Google Brown sludge but only found references to car radiators.

As my system is sealed hopefully brown sludge won't be a problem, but I am alarmed at the amount of black sludge I have come across in the loft pipes and radiators, which is strange as the magnaclean never seems to get very clogged up. I need to check it again now that I've re-introduced one of the loft radiators.

 

[centralheatking]

I did Google Brown sludge but only found references to car radiators.

As my system is sealed hopefully brown sludge won't be a problem, but I am alarmed at the amount of black sludge I have come across in the loft pipes and radiators, which is strange as the magnaclean never seems to get very clogged up. I need to check it again now that I've re-introduced one of the loft radiators.

You are quite correct water cooled motor vehicles do suffer badly, we did look at automotive with Honeywell but there was no commercial traction so we both walked away It is not for me to criticise
any domestic magnetic and strainer type ch filters. Its been at least a decade when I designed some..domestic mag filters .not Magnaclean. You might go along your naughty radiators and visible pipes with a magnet and a soft rubber mallet...thats quite good
there is an adgitator tool which you can put on a domestic electric drill that was origionally my idea I dont know what they call it ...But I got paid for it as usual...nice holiday.
Chemicals will only maintain the status quo not remove the stuff ...a really good reverse pump out first is good...this should take two men all one day.
centralheatking

 

[milleniumaire]

...a really good reverse pump out first is good...this should take two men all one day.
centralheatking

Is this different to a power flush?

 

[centralheatking]

Is this different to a power flush?

Well a proper power flush ought to incorporate reverse flush in my opinion...the trouble is a proper one really does cost hence naughty boys under quote or even quote but do not do it properly. If it was my gaff...I would take the day off and check it all...others on PF will explain what to watch for .....centralheatking

 

[milleniumaire]

I spent the weekend working on the towel rail in the loft. Removed the towel rail and the valves leaving only the copper tails, to which I attached my hosepipes. The other end of the supply/return pipe was connected together using a speedfit flexible hose. So, I have a loop and I pushed in mains pressure water to one radiator tail and the other tail had a hose with the end in a bucket.
No matter what I did, I couldn't get any water through this setup. Actually, there is a very tiny slither of water coming through, but barely anything.

I tried reversing the hose pipe connections and I tried isolating only one of the pipes (to shorten the length being cleaned i.e. hose pipes on both ends of a single pipe) but still no water came through. These pipes are well and truly blocked!

Last night I put some Sentinel X800 into both pipes in the hope this might loosen up the sludge and I will try flushing through again tonight.

I know Sentinel X800 is used for cleaning systems, but I'm not sure it will "dissolve" the hardened sludge in these pipes enough to move it. Can anyone recommend a better chemical? Would Fernox DS40 be better (it's certainly a lot more expensive).

I'm close to the point of giving up and accepting these two pipes will need to be replaced, but that then makes the job a whole lot more complicated due to access!

Any ideas would be welcome.

 

[centralheatking]

I spent the weekend working on the towel rail in the loft. Removed the towel rail and the valves leaving only the copper tails, to which I attached my hosepipes. The other end of the supply/return pipe was connected together using a speedfit flexible hose. So, I have a loop and I pushed in mains pressure water to one radiator tail and the other tail had a hose with the end in a bucket.
No matter what I did, I couldn't get any water through this setup. Actually, there is a very tiny slither of water coming through, but barely anything.

I tried reversing the hose pipe connections and I tried isolating only one of the pipes (to shorten the length being cleaned i.e. hose pipes on both ends of a single pipe) but still no water came through. These pipes are well and truly blocked!

Last night I put some Sentinel X800 into both pipes in the hope this might loosen up the sludge and I will try flushing through again tonight.

I know Sentinel X800 is used for cleaning systems, but I'm not sure it will "dissolve" the hardened sludge in these pipes enough to move it. Can anyone recommend a better chemical? Would Fernox DS40 be better (it's certainly a lot more expensive).

I'm close to the point of giving up and accepting these two pipes will need to be replaced, but that then makes the job a whole lot more complicated due to access!

Any ideas would be welcome.

Try finding a drain off at the lowest point possible in the whole building put a hose on it with a jubilee clip run to the outside. Then re visit your loft connect mains pressure to one tail.....blank off the other....first thing will be the rads will glug glug but dont touch them yet.
Then give it a gentle blast of mains ..to check connections..when sound open it up you really should get plenty from the drain off hose. usually black stuff. are you sure up in the loft you are on mains ..not tank fed low head pressure. ask away we are here to help
centralheatking

 

[milleniumaire]

Hi, thanks for posting.

Just to clarify, the towel rail and its piping in the loft have been isolated from the central heating system, which is operating as normal.

So, I have a couple of hep20 pipes in the loft which connect to the tails of the towel rail and the other end of these pipes do not connect to anything. I am therefore able to so push mains water through these pipes in isolation of the CH system. Despite doing this, I'm unable to get mains pressure water to pass through either pipe due to the extent of blockage.

As I say, I've tried using X800, which may loosen up the blockage, but I won't know until tonight. I'm trying to determine if there is a better chemical to use in case X800 doesn't work.

Thanks.

 

[centralheatking]

Hi, thanks for posting.

Just to clarify, the towel rail and its piping in the loft have been isolated from the central heating system, which is operating as normal.

So, I have a couple of hep20 pipes in the loft which connect to the tails of the towel rail and the other end of these pipes do not connect to anything. I am therefore able to so push mains water through these pipes in isolation of the CH system. Despite doing this, I'm unable to get mains pressure water to pass through either pipe due to the extent of blockage.

As I say, I've tried using X800, which may loosen up the blockage, but I won't know until tonight. I'm trying to determine if there is a better chemical to use in case X800 doesn't work.

Thanks.

Well its obvious then one side of the rad was a feed the other a return no matter what you do there is no circuit..you might have created the blockage yourself...do a diagram we can all look at it later when we get gnome. centralheatking

 

[milleniumaire]

HI, sorry I'm obviously not explaining myself very well.

Here's the original posted diagram of my CH system (the original posted diagram seems to have disappeared). Notice the loft piping:

So, originally, I disconnected all the pipes in the loft from the supply and return (copper pipes from 1st floor to loft). I then flushed through one of the radiators and pipes and successfully cleared them. This radiator is now connected back up, so the current loft setup is shown as follows:

As you can see now, only ONE of the loft radiators is connected to the CH system and this radiator is working perfectly - it gets red hot. I'm now working on the towel rail, shown in the diagram as Loft En-suite, which is currently disconnected from the CH system, allowing me to work on the towel rail and connected pipes in isolation. Here's how I initially connected up the pipes for the towel rail to create a small isolated "circuit":

Note: The towel rail and the valves connecting the towel rail to the Hep20 plastic piping (via copper tails) have been removed, so I'm now working with ONLY the piping. Each pipe run (supply - red and return - blue) is around 4m, so not very long, but they are obviously well and truly blocked.

The above diagram shows I have connected one end of a hose pipe (yellow) to the tail of the supply pipe and the other end is connected to an outside tap, with mains water pressure. Another hose pipe (green) is connected to the tail of the return pipe, with the other end of the hose pipe in a bucket ready to catch the sludge. Between the flow and return pipes I have fitted a flexible hose, so I now have a circuit of piping.

When I turn on the outside tap, the water should end up in the bucket! But I get nothing because the pipes are well and truly blocked. I've tried the following circuits to reduce the length of pipe being cleaned, so I'm doing one pipe at a time:

I've tried the above setup on both the flow and on the return and reversed the hose pipes to flush from both ends, but can't get water through either pipe (apart from the smallest of drizzles).

So, last night I put some X800 into the tails of each pipe until it started (very,very slowly) leaking out of the other end of the pipe, so I knew it had gone through, or at least it was pushing water out. By tonight, this concentrated X800 will have been in for 24 hours and I will attempt to flush the pipes through again.

However, I'm not convinced that X800 is actually the correct chemical to use as I've read it doesn't dissolve sludge, which is what I need it to do, hence the question about other chemicals that may do a better job.

 

[centralheatking]

It would seem you really do have a severe blockage, have you been along with a magnet ? you could also be gently aggressive with a wood mallet or a rubber hammer. I will ask my friends at Sentinel in Runcorn about really naughty chemicals that you might get...not ones you can purchase ...unless others on PF can help chking

 

[milleniumaire]

Unfortunately, I can only access the pipe in the eaves, not the pipe running under the floorboards between the joists, which are full of wool type insulation.

I have had an idea though. I have a long piece of thick, malleable wire that I use for those DIY jobs that require cable to be fed through difficult to access holes etc. I can probably push this in from the eaves end of the pipe although I don't think it is long enough to reach the other end. There will be a 90 degree elbow joining the copper tail to the plastic pipe, so wouldn't be able to access this end with the pipe unfortunately as it wouldn't get around that bend.

If I have no success flushing again tonight (after the X800 has had time to work/not work) I may try using the wire, but as a last resort if the above fail, I would be tempted to nuke the pipes with more chemicals

 

[centralheatking]

HI, sorry I'm obviously not explaining myself very well.

Here's the original posted diagram of my CH system (the original posted diagram seems to have disappeared). Notice the loft piping:

View attachment 41439

So, originally, I disconnected all the pipes in the loft from the supply and return (copper pipes from 1st floor to loft). I then flushed through one of the radiators and pipes and successfully cleared them. This radiator is now connected back up, so the current loft setup is shown as follows:

View attachment 41440

As you can see now, only ONE of the loft radiators is connected to the CH system and this radiator is working perfectly - it gets red hot. I'm now working on the towel rail, shown in the diagram as Loft En-suite, which is currently disconnected from the CH system, allowing me to work on the towel rail and connected pipes in isolation. Here's how I initially connected up the pipes for the towel rail to create a small isolated "circuit":

View attachment 41441

Note: The towel rail and the valves connecting the towel rail to the Hep20 plastic piping (via copper tails) have been removed, so I'm now working with ONLY the piping. Each pipe run (supply - red and return - blue) is around 4m, so not very long, but they are obviously well and truly blocked.

The above diagram shows I have connected one end of a hose pipe (yellow) to the tail of the supply pipe and the other end is connected to an outside tap, with mains water pressure. Another hose pipe (green) is connected to the tail of the return pipe, with the other end of the hose pipe in a bucket ready to catch the sludge. Between the flow and return pipes I have fitted a flexible hose, so I now have a circuit of piping.

When I turn on the outside tap, the water should end up in the bucket! But I get nothing because the pipes are well and truly blocked. I've tried the following circuits to reduce the length of pipe being cleaned, so I'm doing one pipe at a time:

View attachment 41442

I've tried the above setup on both the flow and on the return and reversed the hose pipes to flush from both ends, but can't get water through either pipe (apart from the smallest of drizzles).

So, last night I put some X800 into the tails of each pipe until it started (very,very slowly) leaking out of the other end of the pipe, so I knew it had gone through, or at least it was pushing water out. By tonight, this concentrated X800 will have been in for 24 hours and I will attempt to flush the pipes through again.

However, I'm not convinced that X800 is actually the correct chemical to use as I've read it doesn't dissolve sludge, which is what I need it to do, hence the question about other chemicals that may do a better job.

Unfortunately, I can only access the pipe in the eaves, not the pipe running under the floorboards between the joists, which are full of wool type insulation.

I have had an idea though. I have a long piece of thick, malleable wire that I use for those DIY jobs that require cable to be fed through difficult to access holes etc. I can probably push this in from the eaves end of the pipe although I don't think it is long enough to reach the other end. There will be a 90 degree elbow joining the copper tail to the plastic pipe, so wouldn't be able to access this end with the pipe unfortunately as it wouldn't get around that bend.

If I have no success flushing again tonight (after the X800 has had time to work/not work) I may try using the wire, but as a last resort if the above fail, I would be tempted to nuke the pipes with more chemicals

There is sentinel ..deposit remover.. which is supposed to be really naughty hot or cold....Its a bit off the wall but we used to use my 140amp arc welder to heat up frozen pipes years ago...this would certainly get to the parts you cannot reach.
Attatch the earth clamp to bare copper pipe and run big fat cable 10m 20m away to another earth clamp switch on bingo after a while. Do not do short lengths of pipe as you might vapourise the copper...fun in my workshop it was when we had had a few tins. centralheatking

 

[milleniumaire]

Tried flushing the return pipe again today but no luck. It is blocked solid so I'm going to have to cut up the floor under the radiator to get access to the elbow as I'm 99% sure this is where it is blocked. Given that I'm having to cut floorboards I may bring forward my plan to add new pipes to remove the star type plumbing that currently exists.

 

[centralheatking]

Tried flushing the return pipe again today but no luck. It is blocked solid so I'm going to have to cut up the floor under the radiator to get access to the elbow as I'm 99% sure this is where it is blocked. Given that I'm having to cut floorboards I may bring forward my plan to add new pipes to remove the star type plumbing that currently exists.

Really feel for you mill... keep up with us ....chking

 

[quality]

this is only caused by all these older systems running on modern equipment

 

[loftissue]

I've now successfully cleared the return pipe from the towel rail. Had to cut up the floor boards to get access to the 90 degree connector, connecting the plastic pipe to the copper tail. To my surprise this connector wasn't the issue! When I remove it I pushed some wire into the pipe and about 0.5 metre in it hit something solid, but I was able to eventually push through it. Got lots of solid sludge on the wire! I then realise there was a straight connector at this point of blockage, so clearly the pipe inserts had provided something for the sludge to build up against. I guess pipe inserts are one of the issues with plastic piping and an advantage of copper piping where the bore doesn't get reduced.

Having cleared the blockage with wire I was then able to flush the pipes through and clean out the crud. Tonight I'll be re-connecting the towel rail, with some new valves and will push more water through to flush again and to ensure the joints are water tight. In the morning I'll re-connect the towel rail to the CH system.

Regarding the original wiring of the loft radiators and towel rail, I'm wondering if the orientation of a T connector can make any difference to the flow of water. In particular on the return side, which seems to be the worst blocked pipes. Here's what I mean:

View attachment 41572

On the left is a diagram showing the orientation of the T connectors as they were. The return from the Loft en-suite towel rail and loft 1 radiator is potentially pushing against each other and causing a resistance. Same when that (reduced?) flow hits the flow from the loft 2 radiator prior to going down the copper pipe.

I wondered if changing the orientation of these two T connectors might help the return flow as shown in the diagram on the right. In the alternate diagram the flow from the loft en-suite towel rail has an "easy path" and I wonder if the flow from loft 1 would not give as much resistance. Same with the connector from Loft 2.

Or am I talking rubbish?

Hi there, husband and I are following this thread in the hope we can fix our loft rads. We had a loft conversion installed last year and the 3 rads do not get hot, or come on ever so slightly ( radiator is warm at the top but cold from middle downwards). May we ask if you managed to fix the problem to get all 3 working correctly after flushing the blockages yourself? Thanks.

 

[centralheatking]

this is only caused by all these older systems running on modern equipment

agree totally, old boilers like my Mrs ! have water pathways thro the size of the M6 and are great and lasted 20 years plus. whereas
modern ones the pathways are clearance of a rolling ciggy *** paper. The consequences were with
old boilers a new pump, new boilers total replacement ..and intermediate component failure
centralheatking

 

[loftissue]

Hi there, husband and I are following this thread in the hope we can fix our loft rads. We had a loft conversion installed last year and the 3 rads do not get hot, or come on ever so slightly ( radiator is warm at the top but cold from middle downwards). May we ask if you managed to fix the problem to get all 3 working correctly after flushing the blockages yourself? Thanks.

We've been told to replace the 15mm plastic pipes with 22mm and have a separate flow and return from boiler to loft, instead of an extension of current heating circuit. Was this what you did? Thanks for any help.

 

[quality]

M6 standard would be 1.0mm which is large compared to most modern stuff. But that is all there is avaiable so here we go. There is not a great deal of engineering (maybe not needed) that goes into heating a house with modern stuff

 

[milleniumaire]

Hi there, husband and I are following this thread in the hope we can fix our loft rads. We had a loft conversion installed last year and the 3 rads do not get hot, or come on ever so slightly ( radiator is warm at the top but cold from middle downwards). May we ask if you managed to fix the problem to get all 3 working correctly after flushing the blockages yourself? Thanks.

If your radiators are getting warm at the top , but cold from the middle downwards, that suggests to me they are full of sludge. Have you tried removing them and flushing them through outside? Having said that, it's hard to imagine they have sludged up so much in only 1 year, so maybe flow may be the issue.

I did successfully remove the sludge from all the pipes in the loft, but it took a long time and required me to take up floorboards under the radiators so I could remove T joints/elbows to push in long pieces of wire to dislodge the incredibly hard sludge that had built up at various places within the pipe (connections) and which couldn't be removed by chemicals.

Last year I refurbished the house bathroom and installed wet underfloor heating. I needed to run a brand new flow and return to the bathroom, which is at the other end of the house to the boiler, so designed this to also provide a new flow and return for the loft. I ended up installing two new runs of 22mm pipe which provided the loop (supply and return) for the new bathroom underfloor heating manifold, but also for the loft radiators, by fitting a Honeywell 2 port valve, just after the UFH manifold supply. I also took the opportunity to modify the routing of the pipes in the loft so that it was no longer a "star", and they are now connected up in parallel i.e. one after the other. In addition to this, and at the advice of a heating engineer I use, I also had a Low Loss Header installed and an additional pump, both of which I'm sure would help with flow rates in my system.

So far, I haven't had any further issues with the loft radiators, but I also ensure their valves are always fully opened to keep water moving through them. In the Summer, when the CH isn't really being used, I tried to remember to turn it on every week or so. When I say turn it on, I mean increase the temperature of the thermostat so that there's a demand for heat and leave it like that for an hour.

My system is getting quite complicated and now looks like this: