Central Heating Nightmare - Air in System Daily

[Cellophaneskies]

It’s all sounding too weird though. feels like you need to go back to basics. After the system has been off for the day leave all the rads on and the boiler OFF and go around the house and see if you can bleed air from the rads.

I’ve done this. Last five days. I don’t get any air from the rads in the traditional sense (ie water comes out of bleed valve straight away). But the heating performance is poor. Trickling noises, especially if I turn all thermostats off aside from LR and EXT - then it sounds like a waterfall.

 

[ATTQ]

I’ve done this. Last five days. I don’t get any air from the rads in the traditional sense (ie water comes out of bleed valve straight away). But the heating performance is poor. Trickling noises, especially if I turn all thermostats off aside from LR and EXT - then it sounds like a waterfall.

waterfall and trickling noises are water falling through air. If the air doesnt come out then you have an air lock / pocket at least partially. Find where the noises are exactly and consider adding an air vent in highest part of that area.

 

[Cellophaneskies]

was just thinking that, it must be losing water but then drawing air in when running. Faulty pressure relief valve?

Is water dripping out of the pipe at the back of your house?

No drips whatsoever - no corrosion signs or water on wall. I never see pressure rise (aside from ever so slight when it’s running)

 

[ATTQ]

No drips whatsoever - no corrosion signs or water on wall. I never see pressure rise (aside from ever so slight when it’s running)

so where is the water going? Only other way I can think where you might not notice it is through the domestic hot water heat exchanger has that been looked at? But that doesn't explain how air gets in

 

[ATTQ]

adding an air vent isn't really the full solution of course, its treating the symptom not the disease. Because you say you can successfully clear the air after a drain it must be finding its way in even after closed

 

[Cellophaneskies]

so where is the water going? Only other way I can think where you might not notice it is through the domestic hot water heat exchanger has that been looked at? But that doesn't explain how air gets in

Not a clue, this is what I’m going nuts!

My personal suspicion - and last straw - is that the two drops of pipes form upstairs to downstairs are still original and have not been replaced. They’re approx 15 years old and not a professional install. So I’m thinking perhaps there is corrosion inside or something.

Also one rad is original but again it’s like 15 years old or so and I have flushed it. Even when isolating ther from the system the issue still occurs so I’m not particularly suspicious of it but could replace it for the sake of £50..

If I were to replace those drops and it still happens then I’d be getting an exorcist in.

To confirm, pressure doesn’t change if I don’t touch it. No leaks. No rise.

 

[ATTQ]

If it doesnt rise or fall, and no air comes out of the rads, you must just have an air pocket in the pipes. But why would it get worse after it has been ok...

 

[Cellophaneskies]

If it doesnt rise or fall, and no air comes out of the rads, you must just have an air pocket in the pipes. But why would it get worse after it has been ok...

Not sure! One of the bleed valve in the pipework for draining doesn’t give any flow when loosened so perhaps that is dodgy but I’d expect a leak if that was the cause.

In the pipework up to bathroom there is a 90 degree bend to get it away from the joist as it goes into ceiling.. perhaps this is an issue.. it’s the only remaining oddity in the install but it’s just a normal angle.

Ignore water marks on wall. During my bleeding endeavours once the bleed valve broke and the BR radiator lost its contents all over me and the floor..

 

[ATTQ]

that wouldn't trap air. Might be an old redundant loop somewhere. If you can hear the water trickling that is the sound of water falling through an air pocket so you should be able to find it roughly by that

 

[ATTQ]

I guess an air separators is designed just for this where an automatic air vent isn't doing it and there is an issue with the system design. Still feels like a bodge rather than proper correction but if thats easier than getting the boards up and changing the pipes it might be the right solution for now.

SpiroCombi - Air deaerator & Dirt separator

Deaerators/dirt separators specially designed for the simultaneous removal of air and dirt from water systems. These remove air, microbubbles and dirt particles from system water continuously.

www.spirotech.co.uk

 

[Cellophaneskies]

I guess an air separators is designed just for this where an automatic air vent isn't doing it and there is an issue with the system design. Still feels like a bodge rather than proper correction but if thats easier than getting the boards up and changing the pipes it might be the right solution for now.

SpiroCombi - Air deaerator & Dirt separator

Deaerators/dirt separators specially designed for the simultaneous removal of air and dirt from water systems. These remove air, microbubbles and dirt particles from system water continuously.

www.spirotech.co.uk

So I’ve seen the entire pipework run and it’s all pretty by the numbers. No offshoots, no redundant parts.. in fact a few in the ago the ‘backbone’ was entirely upgraded to 22mm from 15mm. Previous person to mess with it had installed two shut off valves in line to BR. These were also removed.

When the system is running well now, it gets INSANELY hot, so the upgrade to pipework made a difference- but the degradation of the system and air issue is unchanged!

Between B2 and LR there used to be a weird ‘up and over’, upside down U shape over a joist. So I thought this might be the culprit. This was removed and the problem didn’t change!

 

[ATTQ]

Yes nightmare. Feels like one of those things where in the end it will turn out to be something stupidly simple that has been overlooked. Is the water coming out of your cold tap full of bubbles?

 

[ATTQ]

how can there be air in the system that doesn't rise to the top of the radiators but only comes out when the boiler is running?

 

[Johntheo5]

I think the whole system should be drained down, refilled at least once and drained down again, then refilled with no inhibitor added, then run at a moderate flow temp of say 50/55C, if no problems then gradually increase flow temp to required level.

I would also certainly consider installing a Spirovent at the highest point on the flow side, even if it does nothing more after removing all the air then money well spent.

 

[fixitflav]

Here's a paintmash. Yellow is walls. Red line is the piping route, representing both supply and return - they run in a pair each way

Nothing that jumps out from the sketch. If it hasn't been covered, what pressure is it at? Raising it if possible would reduce the risk of air being sucked in somewhere.
Is it a normal sized house ie upstairs rads max ~3m above boiler?