Help needed to understand the purpose of another pipe and valve for expansion tank

[papaya]

Evening guys,

I'm slowly learning how my central heating system works and I would like to ask for your help to understand the purpose of the pipe and valve used with my expansion tank as I can't see the point there :disappointed:


I understand that the white pipe (bended) is overflow and the one with green insulation is the cold feed to the F+E and the other high paper clip type pipe is the expansion pipe for extra protection as all water through it will eventually drop back to the tank BUT I don't seem to understand the one on the right with the valve (circled).



The reason is that this valve controls the water from expansion tank to flow with the hot water from the left through the heater pump. If I turn it off, just the hot water from left will come through to the pump but if I turn it on, it will mix with the hot water comes from left and results in only cold water come through the pump. So what's the purpose of that and should I leave it on or off? I know it sounds stupid but I can't figure out why...


In addition, I would also like to know how could I check if the copper coil in my water cylinder has pinholes?

Many thanks! :blush5:

 

[Whyme]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

The valve is on the cold feed to ur heating, leave it open as expanding water uses it. Why do you think the coil has pin holes ??

 

[ecowarm]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

In addition, I would also like to know how could I check if the copper coil in my water cylinder has pinholes?

If your copper coil had pinholes the f&e tank would be constantly overflowing as the level in the 2 tanks try to equalise
​

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Whyme, many thanks for your quick reply.

For the pinholes, it is because my overflow is always dripping when the boiler is not on and I had discoloured hot water. I thought it was a coincidence as the discoloured water just happened after Wessex water did some work but when I called a plumber in to change our faulty motorised valve, he told me there are pinholes in the coil. The reason is that when he disconnected primary flow to replace the 3 port valve, there was water dripping from it and I could hear some hissing.

Any suggestions?

Thanks again!

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

ecowarm, thanks but mine stops when the boiler is working - either heating or hot water or both.

 

[diamondgas]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

It is a NO---NO .. to have a valve where you have!!!

Dodgy DIYer or plumber ALERT!!! :50:

 

[Mike Jackson]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

I agree. It's actually illegal under the water regs (of all things) to have any sort of isolating or service valve on the outlet of an F&E tank in a domestic dwelling.

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

It is a NO---NO .. to have a valve where you have!!!

Dodgy DIYer or plumber ALERT!!! :50:

Thanks to clarify this but what's the purpose to have one then if this is not a good idea? I'm just trying to understand it.

 

[Mike Jackson]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

This is the cold feed to the heating system. The pipe needs to be there but not the valve.

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

I agree. It's actually illegal under the water regs (of all things) to have any sort of isolating or service valve on the outlet of an F&E tank in a domestic dwelling.

I know the previous owner of my flat is a builder and I'm not sure whether he did that or not... :-(

 

[Mike Jackson]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

I know the previous owner of my flat is a builder and I'm not sure whether he did that or not... :-(

I've seen plenty fitted by people who should know better.

 

[diamondgas]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Thanks to clarify this but what's the purpose to have one then if this is not a good idea? I'm just trying to understand it.

It's a 'lazy man's' way of not having to drain off the bucket of water in the header tank!! BUT can cause all sorts of grief if inadvertently closed and left that way!! It also closes off the means of accomodating system water expansion so therfore the open vent pipe has to take over its roll!!

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

So does it mean the cold feed is used in conjunction with TRVs of radiators to control temperature?

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

It's a 'lazy man's' way of not having to drain off the bucket of water in the header tank!! BUT can cause all sorts of grief if inadvertently closed and left that way!! It also closes off the means of accomodating system water expansion so therfore the open vent pipe has to take over its roll!!

It sounds scary but thanks for explaining this!

 

[diamondgas]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

So does it mean the cold feed is used in conjunction with TRVs of radiators to control temperature?

What's your concern papaya?

Your pictures show a close coupled feed and vent and a concern regards the pump getting cold water drawn through it!! The set up is asking for trouble with the potential for ingress of 'fresh' water, it being 'close coupled' ...

What's your concern though? TRV's have nothing to do with the header tank!

 

[Mike Jackson]

So does it mean the cold feed is used in conjunction with TRVs of radiators to control temperature?

No. It just keeps the system full of water.

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

I was trying to figure out why my radiators are cold when the CH is on as when I touched microbores connected to primary flow, they were cold. I traced all pipes up to my loft and eventually discovered that, so I thought it could be a problem as hot water mixes up with cold water. So like you said, regarding the water ingress, what will be the best solution then? Sorry my knowledge of plumbing is poor.

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

No. It just keeps the system full of water.

I see, thanks!

 

[Crinkmeister]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

I was trying to figure out why my radiators are cold when the CH is on as when I touched microbores connected to primary flow, they were cold. I traced all pipes up to my loft and eventually discovered that, so I thought it could be a problem as hot water mixes up with cold water. So like you said, regarding the water ingress, what will be the best solution then? Sorry my knowledge of plumbing is poor.

I don't think the person who installed that system knew much either!

 

[thompsonbrown]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

pipe is cold feed to central heating system if you don't think you need it try filling your heating system after a rad swap. also its in the wrong place to close to the pump and should be tee'd in from underneath

 

[Mike Jackson]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Doesn't have to be teed in from underneath (in fact looping underneath means there is more likelihood of the cold feed blocking) and no issue with the proximity to the pump. There may be issues with the open vent as I can't see exactly where it is connected and it has been raised very high, presumably to resolve a pumping over issue. I'm assuming that the pump is pumping left to right in the picture.

 

[thompsonbrown]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

i would check out the cold feed best practice guide, i was always taught that by feeding the heating system from underneath that it would have less chance of drawing air from the f&e tank also less chance of dragging air into the system when filling do you have any evidence of this changing since 1986 i would really like to know if it has but you are correct about the positioning of the pipe.

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Doesn't have to be teed in from underneath (in fact looping underneath means there is more likelihood of the cold feed blocking) and no issue with the proximity to the pump. There may be issues with the open vent as I can't see exactly where it is connected and it has been raised very high, presumably to resolve a pumping over issue. I'm assuming that the pump is pumping left to right in the picture.

Mike, you are right the pump is pumping left to right as this can be identified by touching the pipe when the valve is open as cold water will go thru from left to right.

 

[diamondgas]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

I was trying to figure out why my radiators are cold when the CH is on as when I touched microbores connected to primary flow, they were cold. I traced all pipes up to my loft and eventually discovered that, so I thought it could be a problem as hot water mixes up with cold water. So like you said, regarding the water ingress, what will be the best solution then? Sorry my knowledge of plumbing is poor.

With the limited knowledge you have I'd advise you get someone in However in the mean time, did all your radiators go off at the same time or was it a gradual reduction? What sort of boiler do you have? Room thermostat fitted? Diverter valve fitted?

Realy need to know a bit more about your system design to give you a better idea of what the possible issues may be IMO

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

With the limited knowledge you have I'd advise you get someone in However in the mean time, did all your radiators go off at the same time or was it a gradual reduction? What sort of boiler do you have? Room thermostat fitted? Diverter valve fitted?

Realy need to know a bit more about your system design to give you a better idea of what the possible issues may be IMO

Thanks diamondgas. I have a Worcester Greenstar 18 Ri, my central heating system is vented (the common one before 2000). For my radiators, the problem is that they take ages to heat up and usually they just stay cold. I have a thermostat in the corridor and have a 3 port motorised diverter valve. I have asked my plumber to check it today and he said my cylinder keeps generating air to the whole system because of damages in the coil so it cannot be properly solved unless the cylinder is replaced. He has tried to release air lock and now we have lukewarm water - better than no hot water at all.

Now I have a question, if I turn off all radiators, turn off the control and turn off the cold feed for expansion so that cut off the radiator circulation from the system and just leave the hot water circulation in the system. In that case, will my hot water be back normal?

Thanks again,

 

[Dannypipe]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Don't cut off the cold feed to the feed and expansion tank. As said, there shouldn't be a valve there anyway.

If the coil has pin holes in it then that could explain the dirty water at your taps.

However it could be other factors.

If your feed and expansion tank starts to over fill and the overflow runs, then you have pin holes in the coil. The water will try (as said) to balance at the tanks.

However deal with one issue at a time. Your radiators are all cold. Correct?

You're hot water isnt getting hot either?

Have you checked the pump?

 

[helpsy]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Cold feed 15 mm

 

[Dannypipe]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Cold feed 15 mm

Well Helpsy, that was insightful. Helpful even. !!!

Anyway, i'm off to bed. Good luck with your endevours OP. I reckon you may need a second opinion, maybe get someone from the forum to take a look. Your man may have got misguided. Happens to us all at times.

 

[helpsy]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Wondering if the neutral point is blocked as vent pipe excessively high (450 above water level) pumping over

 

[Whyme]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

like i and many said dont turn off the valve. best bet is get a plumber round and give you a real life hands on diagnosis because theres only so much can be said over tinternet

 

[diamondgas]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Thanks diamondgas. .... he said my cylinder keeps generating air to the whole system because of damages in the coil so it cannot be properly solved unless the cylinder is replaced. ...

Thanks again,

That is absolute ball cocks IMHO It sounds like you have circulation problems most likely associated with the configuration you show in your pictures. As Danny suggests, get a second opinion. Without checking the functionality of your pump and valve it's difficult to give advice. One thing to consider and maybe discuss with an 'expert' would be sealing the heating system or at least combining the feed and vent to overcome the possibility of air ingress. Depending on the state of the system will determine whether any further work such as a flush would benefit your system? As mentioned, put up a request on here and at least you can check out to some degree the person's credentials before contacting them ... [DLMURL="http://www.ukplumbersforums.co.uk/im-looking-plumber-gas-engineer/"]I'm looking for a Plumber or Gas Engineer[/DLMURL] ​

 

[Gerard17]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Just put a combi in

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Many thanks everyone for your advice and suggestions. I will ask for a plumber here

 

[Dannyparty92]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

What are the regulations on service valves on heating cold feeds? And I know it's wrong as a few of you have mentioned but why is it wrong? Because most heating systems have gate valves on the cold feed just not as close to the f and e tank.

 

[WHPES]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

I came across a double check valve on the (15mm) vent pipe of a F&E cistern recently signed off by a building inspector!!!

If not already mentioned, OP your water level in the cistern may be too high. When cold the fill valve should shut off when the water level is about 10cm. Too high and there's not enough room left for water expansion and it will overflow and top up with fresh when cool, causing rapid corrosion.

If you have overpumping, I would recommend conversion to a sealed system if it is appropriate and suitable for your circuit.

 

[deacongas]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

My guess would be the valve was thrown in for a power flush. coupled with push fit 22mm stop end on vent pipe seals the system temporarily for flushing. not a great idea to leave the valve attached just in case somebody decides to close it off though...doh!

 

[Mike Jackson]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

What are the regulations on service valves on heating cold feeds? And I know it's wrong as a few of you have mentioned but why is it wrong? Because most heating systems have gate valves on the cold feed just not as close to the f and e tank.

There should be no valves between the boiler and the F&E tank to ensure that there is an uninterrupted path to allow for the expansion of heated water. If the valve is inadvertently closed the expansion will take place up the open vent and may spill over into the F&E tank. This will lead to a reduction in the volume of water in the system and can lead to overheating. It's arguably less important with modern boilers as they have an overheat stat but they can still be damaged. On older boilers with no overheat stat it can lead to water within the system boiling.

Think of the cold feed and F&E tank as being equivalent to the expansion vessel on a sealed system. Shutting the cold feed off is like fitting a sealed system with no expansion vessel.

 

[Dannyparty92]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Cheers mike Christ iv seen so many systems with gate valves on the cold feed.

 

[Dannypipe]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

When I power flush I tend to plug the tank with a rubber bung like this:


Not cheap, but won't blow out. I then wet vac out the tank so I don't draw any sludge from inside down the cold feed.

You buy them from Today's tools. Had mine for years.

Here's one link:

Squeeze and Fix Repair Sets - Buyriteuk.com - BuyriteUK

Pricey for what they are though. I didn't pay that much for them.

 

[Mike Jackson]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

The jet swet ones look very good. They look like they'll fit through the tank connectors with the projections on the inside.

 

[Dannypipe]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

The jet swet ones look very good. They look like they'll fit through the tank connectors with the projections on the inside.

They do look good but they're really expensive!

 

[Reg Man]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

My guess is that because this is such a low head system, that its had pumping over problems, so somone has turned the pump down to its lowest setting to prevent pumping over. The draw back to this, is that now there is not enough circulation to get round the radiators.

Best solution is do away with the F&E cistern and convert it to a sealed system with expansion vessel, PRV, Pressure gauge and filling loop.

 

[Dannypipe]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

My guess is that because this is such a low head system, that its had pumping over problems, so somone has turned the pump down to its lowest setting to prevent pumping over. The draw back to this, is that now there is not enough circulation to get round the radiators.

Best solution is do away with the F&E cistern and convert it to a sealed system with expansion vessel, PRV, Pressure gauge and filling loop.

Yeah you could be on to something there.

 

[Mike Jackson]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

It could also lead to a world of hurt on an old system.

 

[Dannypipe]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Upgrade the feed to 22mm and have a combined feed/vent pipe.

Or move the pump?

Needs looking at and sorting properly.

You could seal the system but doesn't have to be at 1 bar static pressure, could be lower to prevent straining the old system (if that's your concern).

 

[Dannyparty92]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

reg man? so you mean when the heating is on the pump surges and forces water into the cistern from the vent pipe because the pump is so close to the level of water in the f and e tank?

 

[Reg Man]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

reg man? so you mean when the heating is on the pump surges and forces water into the cistern from the vent pipe because the pump is so close to the level of water in the f and e tank?

The area before the pump where the open vent and cold feed are, is the negative pressure zone. On occassions of low head systems with high resistant systems. The pump will have to be set quite high to get the circulation. This can cause air in the system and pumping over.

As said before, your options are, Sealed system or raising the F&E cistern and repositioning the pump.

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

My guess is that because this is such a low head system, that its had pumping over problems, so somone has turned the pump down to its lowest setting to prevent pumping over. The draw back to this, is that now there is not enough circulation to get round the radiators.

Best solution is do away with the F&E cistern and convert it to a sealed system with expansion vessel, PRV, Pressure gauge and filling loop.

Regman, we have microbores so a sealed system sounds like we will get a little chance that the pipes would burst

 

[Reg Man]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Regman, we have microbores so a sealed system sounds like we will get a little chance that the pipes would burst

If you go the sealed option route, then check the condition of the exisisting pipes and valves to make sure there up to slightly higher pressure. 1.5bar = about 15 metre head of pressure (49ft)

 

[Dannyparty92]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

It would pump over even if the vent is just before the pump on the negative side?