Always getting air lock when refilling system

[markyhud]

I have drained and refilled my system a few times (with some cracking advice off here) and each time I still end with an air lock. After draining down I re-open the valve in the f&e tank in the loft, let it fill and then start bleeding downstairs rads first to encourage filling. Once all the downstairs is done I move upstairs and again bleed each rad in turn I then bleed the screw on the pump and finally the vent in the airing cupboard next to the coil. I then have the boiler set at 0 and turn on hot water for a few seconds, go upstairs and bleed the pipework again. I repeat this a few times and then turn on the hot water and turn the boiler up. I then switch off the hot water and then turn on the central heating by itself. I work round each rad and bleed any air.
After all this I still end up with air in the pipework and coil. Grrrrrr!!!
As the system is initially refilling should I leave the vent open next to the coil to encourage filling of the airing cupboard pipework?
I was thinking of partially draining it down (via lowest rad) and then using cold mains water and refill from the bottom up. I am hoping this would fill the pipework and coil and push any air up into the tank in the loft. Is this feasible?

 

[mountainman]

My advice would be to stop draining and refilling the system.
I believe that there is a support group for OCDDD.
(obsessive compulsive draining down disorder)

 

[markyhud]

My advice would be to stop draining and refilling the system.
I believe that there is a support group for OCDDD.
(obsessive compulsive draining down disorder)

Very good mate. I'll have to get that CCTV taken out of this house!!
On another note could it be the F&E tank being too full. Can this have an effect on air? How full should it be?

 

[mountainman]

One third full is about right.
Why do you keep draining the system???

 

[markyhud]

I don't keep draining it to be honest. I've done it a couple of times over the past few years. I recently asked on these forums which is the best cleaner to use as it has never been cleaned in it's 14 year life. Had settled on fernox f3 but just not had time to drain it down and add it. I looked in the loft the other day and the water in the f&e tank was brown!! Today i've drained it down and cleaned this tank out. It was full of orange/brown/rusty water at the bottom. So I think this might possibly be causing the gassing and the kettling noise. I still haven't added the cleaner as I haven't got round to buying it. Anyway I was very careful when refilling but it still gurgles through the pipework and coil when the hot water is first turned on

 

[Ch4 plumbing]

Have you got any of these on the F/R to the cylinder? If not cut one into the return pipe and that will help get rid of air at that point.

 

[markyhud]

Yeah this is where I am having to bleed air from probably once a week.

The hot water seems to gurgle when first turned on but this has possibly been caused by the rusty water in the header tank. Now I've cleaned that out I'm hoping the noise settles but immediately after re-filling and carefully bleeding it's gurgling again at the airing cupboard.
What effect if any does it have if the header tank is too full?

What about blasting the air out by attaching cold water mains to the lowest drain point?

 

[diamondgas]

In my experience you'll always have a settling period where the air will find its way to somewhere or tother and stay there! How do you know you have airlocks?

"Rusty water in the header tank!" .... That's something to raise the 'something dodgy there' eyebrow Is the system 'pumping over'? Water warm/hot in the header tank at anytime?

 

[markyhud]

The house was newly built 14 years ago and the CH hasn't had much TLC until the last few years. In fact I've only paid attention to the F&E tank today. It was manky!!!! And I did notice afterwards that the pump was pumping over via the vent pipe when it was set to speed 3. At setting 2 (where I normally have it) it is fine but I did notice the level was quite high. In fact the L shaped piece of the overflow is submerged in the water.
I tend to vent/bleed the system and then within a few weeks it becomes noisy again. However today it started gurgling immediately after refilling so I think I may be doing something incorrect when refilling and trapping air somewhere.
Basically I've got 2 issues
1. Long term air/gas that needs occasionally venting and is noisy
2. Problems re-filling the system without getting air trapped.

 

[diamondgas]

The house was newly built 14 years ago and the CH hasn't had much TLC until the last few years. I've I by really paid attention to the F&E tank today. It was manky!!!! And I did notice afterwards that the pump was pumping over via the vent pipe when it was set to speed 3. At setting 2 (where I normally have it) it is fine but I did notice the level was quite high. In fact the L shaped piece of the overflow is submerged in the water.
I tend to vent/bleed the system and then within a few weeks it becomes noisy again. However today it started gurgling immediately after refilling so I think I may be doing something incorrect when refilling.

'L' shaped pipe sounds like a bylaw kit! Only necessary on a domestic feed tank I believe? ... however pumping over is a serious problem ... clearing air depends on the pipework configuration and pump position ... Check for pumping over on water only, heating only and then both on together! If it occurs on any I'd advise you get a decent plumber in who knows how to overcome the issues...!

Continual venting may be an indication of 'active corrosion'/pumping over or 'surging' occuring ... IMO

 

[Ch4 plumbing]

Can you take a photo of the pipe work above the pump? I wonder if the configuration is slightly wrong.
if the water in the f/e tank is very hot it will expand and be fuller then normal.

 

[markyhud]

'L' shaped pipe sounds like a bylaw kit! Only necessary on a domestic feed tank I believe? ... however pumping over is a serious problem ... clearing air depends on the pipework configuration and pump position ... Check for pumping over on water only, heating only and then both on together! If it occurs on any I'd advise you get a decent plumber in who knows how to overcome the issues...!

Continual venting may be an indication of 'active corrosion'/pumping over or 'surging' occuring ... IMO

Do you think it would still benefit from a cleaner added followed by an inhibitor? It's had nothing added in its lifetime.
It only pumped over when set on speed 3. I never have it on that speed

 

[diamondgas]

Do you think it would still benefit from a cleaner added followed by an inhibitor? It's had nothing added in its lifetime.
It only pumped over when set on speed 3. I never have it on that speed

IF you know for certain that the system isn't pumping over in the 3 scenarios I mentioned then get a magnetic filter fitted and dose with inhibitor... Seriously though! If it pumps over on '3' there's a chance that you have pipework configuration issues and possible 'surging' occurring at the least on 1 or 2. In my experience, over the years, this can block/restrict internal pipe diameters and leads to further complications!

However this might not be the case but it's worth while getting it checked out before you go about inhibiting! In my opinion

 

[markyhud]

When u mentioned the 3 scenarios for pumping over would that be at the highest speed or my normal number 2?
I could quite believe its a pipework issue as my neighbour has had issues with noise.
And as for the filter yes this was a definite consideration after Xmas.

 

[diamondgas]

When u mentioned the 3 scenarios for pumping over would that be at the highest speed or my normal number 2?
I could quite believe its a pipework issue as my neighbour has had issues with noise.
And as for the filter yes this was a definite consideration after Xmas.

Now then! Neighbours with similar symptoms points to a usual and common problem (installer) .. pipework configuration from installation! Try your usual setting and see what happens ... Better still find someone on here in your area that knows a thing or two about system design that can best advise..

 

[Jimbob]

Pipework must he incorrect. Get a trained heating engineer in to rectify. Just adding cleaner alone may not sort the issue.

 

[markyhud]

I've come to a couple if conclusions here
1. I've got pipework config issues
2. I need to have a filter fitted

In the interim period though is the technique I used to refill the system correct? Should I have opened that air vent in the airing cupboard to encourage filling of the pipework?

 

[diamondgas]

In the interim period though is the technique I used to refill the system correct? Should I have opened that air vent in the airing cupboard to encourage filling of the pipework?

Generally filling from the bottom up is the usual approach. Air will always be present initially but should easily find a home or escape, in the radiators or out of the open vent pipe is the norm! I usually let the system settle before bleeding radiators or manual vents such as the one at the cylinder, which, by-the-way, is an auto-vent so should vent itself. However they're usually turned off coz they're pretty naff! :lol: If I suspect air trapped in the pipe you mention I'd turn the system off before venting. You can open it whilst its running, it won't do any harm but you might find it spurting on and off..

 

[markyhud]

Generally filling from the bottom up is the usual approach. Air will always be present initially but should easily find a home or escape, in the radiators or out of the open vent pipe is the norm! I usually let the system settle before bleeding radiators or manual vents such as the one at the cylinder, which, by-the-way, is an auto-vent so should vent itself. However they're usually turned off coz they're pretty naff! :lol: If I suspect air trapped in the pipe you mention I'd turn the system off before venting. You can open it whilst its running, it won't do any harm but you might find it spurting on and off..

Cheers. I usually have this auto vent just nipped up to the point of it bleeding a tiny drop of water. Is this right? I always switch it off before bleeding. I have thought about swapping this out for a decent auto vent as I believe these are the cheapest naffest auto vent
I have always filled from top down. So might it be beneficial to fill via the mains and the bottom drain point?

 

[diamondgas]

Cheers. I usually have this auto vent just nipped up to the point if it bleeding a tiny drop of water. Is this right? I always switch it off before bleeding.

that should be fine if it's just passing slightly as long as you've got a cloth at hand and in control If you're still chasing air 24hrs down the line then to me that indicated a poorly positioned open vent. In theory the vent pipe is there to allow air in the system out to atmosphere and should be positioned to accomodate that

 

[markyhud]

that should be fine if it's just passing slightly as long as you've got a cloth at hand and in control If you're still chasing air 24hrs down the line then to me that indicated a poorly positioned open vent. In theory the vent pipe is there to allow air in the system out to atmosphere and should be positioned to accomodate that

I have to say you blokes on here deserve a medal for taking the time to talk to amateurs like me. If I were in your position it would drive me mental!!!
Just one more question honestly as I had edited my last post as you replied. As the system was gurgling away immediately after refilling top down yesterday I'm wondering if it would be ok to fill it with the mains tap connected to the lowest drain point on a rad downstairs. In theory this would push any air upwards and out. If I did this is there any special trickery like turning upstairs rads off first or would I just leave everything open (other than bleed screws obviously)

 

[Killy Bing]

I have to say you blokes on here deserve a medal for taking the time to talk to amateurs like me. If I were in your position it would drive me mental!!!
Just one more question honestly as I had edited my last post as you replied. As the system was gurgling away immediately after refilling top down yesterday I'm wondering if it would be ok to fill it with the mains tap connected to the lowest drain point on a rad downstairs. In theory this would push any air upwards and out. If I did this is there any special trickery like turning upstairs rads off first or would I just leave everything open (other than bleed screws obviously)

that's known as back filling, personally I wouldn't advise you doing it by your todd (we only do it with we have no other option mind!!) if you feel the need then yes you can, you will need someone else sat by the tank to yell at you when the water rises to turn the water off. still I wouldn't advise it !

 

[diamondgas]

:iagree: not advisable and there shouldn't be a need to back fill unless there was an issue with bleeding e.g. the radiators stop bleeding. Back-filling won't necessarily 'get rid' of air and will overfill the system if not monitored!

 

[markyhud]

OK so as soon as I request hot water and I hear the diverter moving that's when the kettling and gurgling starts. I can hear it starting in the pipework leading from the boiler downstairs, through the pump and then it gurgles round the coil. The thing is after about a minute the noise settles and the system stays quiet after that. It's almost as if air is being drawn in from somewhere on start up but then possibly venting from system. How is this possible and what could cause it?

 

[diamondgas]

OK so as soon as I request hot water and I hear the diverter moving that's when the kettling and gurgling starts. I can hear it starting in the pipework leading from the boiler downstairs, through the pump and then it gurgles round the coil. The thing is after about a minute the noise settles and the system stays quiet after that. It's almost as if air is being drawn in from somewhere on start up but then possibly venting from system. How is this possible and what could cause it?

depends on the quantity of 'air' .... Couple of possibilities are 'gas' being generated ... leak on the negative side of the pump ... pipework configuration around the feed and vent ... 'cavitation' ... Just guesses mind If it doesn't settle after a day or two then it's not getting freed. Poor vent position could mean you're chasing air around the hot water circuit for quite a while to be honest..

 

[markyhud]

OK so I took some time to read up on f&e tanks, positioning of vent pipe etc as I am continuosly chasing air round this system. When I loooked at the f&e tank it was about 3/4 full when cold. Now I believe this should be about 1/3 full or approx 100mm. So i bailed some water out and bent the arm of the ball cock. After this I noticed the vent pipe (highest section above the tank before the elbow) was only 300mm above my new water level. From reading I know there is a calculation for the correct height of this and I think mine might be poorly configured. I then started to think that may be the pump was drawing in air through this vent pipe as the system was always very noisy on start up and it seemed like it was starting at the boiler. So I also turned the pump from speed 2 to 1. Initial impressions are that it's quieter but will have to wait and see. It's a 3 bed 2 storey house with 10 rads. They all heat up but some are hotter than others on speed 1. I could put up with this if it will solve the noise issue.
I've also noticed that the auto air vent next to the hot water cylinder actually does vent automatically but in order to do this it has to weep slightly. I have put a towel underneath and keep checking on this as it's obviously not ideal. Are the cannister type auto air vents any better than the cheap slot head threaded type.
I think i'm finally getting somewhere but will definitely need the help of a professional to come and have a look and possibly fit a filter

 

[diamondgas]

Aso you reduce the pump speed you then show up potential system balance issues! Lower speed will emphasise poor balance IMO

Regards the auto vent, a 'float' type are best in my opinion, much better than the 'expanding cloth' type you have fitted?

Thing regarding the open vent; if it's fitted in the correct place you'll not get air drawn in through it......... also to achieve air being drawn in, you have to have a really poorly restricted circulation that produces such a negative pressure on the vent ...? If the reduction in speed reduces the noise then let it run that way till it's quiet then try stepping it up to two! If the noise returns the turn it back down...