Air in radiators

[BigBen]

The radiator in my bathroom needs bleeding on around a twice daily basis. My question is how does the air get into it ? or more accurately how do I find where the leak is.

Obviously a leak somewhere and the bathroom rad is probably the highest point in the system. Any hints on how to 'debug' the system ?

Cheers

Ben

[rash_decision]

BigBen said:

Obviously a leak somewhere and the bathroom rad is probably the highest point in the system. Any hints on how to 'debug' the system ?

Cheers

Ben

I would say it's not necessarily a leak in the bathroom radiator, it could be anywhere, but just appearing at that radiator as it's the highest point in the system.

[RizzoTheRat]

Presumably there must be a fairly limited area the leak could be, ie somewhere just before the pump, as the system should be pressurised by a header tank so most of it will be above atmospheric pressure.

[Ferg]

Micro leak on suction side of pump.
Pulling air down the vent.
Sludge creating hydrogen.
Auto-air vent allowing air in on pump start-up.

Any of these.

[Simpo Two]

Perhaps they should invent a 'belching valve' - that would break wind every so often and break the ice at parties!

[Kermit power]

RizzoTheRat said:

Presumably there must be a fairly limited area the leak could be, ie somewhere just before the pump, as the system should be pressurised by a header tank so most of it will be above atmospheric pressure.

There doesn't necessarily have to be a header tank.

We've recently had a combi boiler fitted, and there is no tank required.

Thinking about this, does that mean we'll never have to bleed a radiator again? I'm assuming the whole system from the road outside onwards is pressurised, so any leak would lead water out rather than air in?

[ThatPhilBrettGuy]

Kermit power said:

Thinking about this, does that mean we'll never have to bleed a radiator again? I'm assuming the whole system from the road outside onwards is pressurised, so any leak would lead water out rather than air in?

They're closed systems so there's a manual method to 'top-up' the pressure if you've had a leak. Water does release gas for a while but after a bit it'll get stable.

[paulshears]

I kept getting air is my system.... also pressure was a bit high too

I tried bleeding the air (and a bit of water) out of just the highest radiator..... didn't solve the problem

Then I bleed ALL the radiators.... started lowest first

Did this twice, just to make 100% sure all the air was gone

Been fine ever since

[BigBen]

ThatPhilBrettGuy said:

Kermit power said:

Thinking about this, does that mean we'll never have to bleed a radiator again? I'm assuming the whole system from the road outside onwards is pressurised, so any leak would lead water out rather than air in?

They're closed systems so there's a manual method to 'top-up' the pressure if you've had a leak. Water does release gas for a while but after a bit it'll get stable.

Just figured out how to re-pressurise the system, that might do the trick as it never used to be this bad.

Ben

[Gingerbread Man]

Ferg said:

Sludge creating hydrogen.

This was one of my thoughts, when next bleeding it, see if it lights with a match.

[squicky]

Gingerbread Man said:

Ferg said:

Sludge creating hydrogen.

This was one of my thoughts, when next bleeding it, see if it lights with a match.

I just had a mental image of a radiator shooting a 6ft flame across the room after trying that...

[King Herald]

It could be gas caused by continual corrosion, ferrous oxide, so some inhibitor might help, and might stop your rads rusting through.

I just added a litre of 'Sentinel' goop to ours, as it has started getting noisy again, and it made an instant difference to the noise level.

[RizzoTheRat]

I put some cleaning stuff in mine, then flushed it all through and refilled it with some inhibitor, made no difference to the gurgling noises it occasionally makes but it now puts out a hell of a lot more heat.

[Simpo Two]

King Herald said:

It could be gas caused by continual corrosion, ferrous oxide, so some inhibitor might help, and might stop your rads rusting through.

Ferrous oxide is a solid - aka rust. Ferg mentioned hydrogen; I was trying to think of the chemistry behind it - what acid might you encounter that would generate hydrogen from copper or rust?

But as squicky says, easy enough to test!

Edited by Simpo Two on Sunday 17th January 15:28

[RizzoTheRat]

3H20 + 2Fe = Fe2O3 + 3H2 I think


ETA:
Hmmm, bit more complicated that it seems as it needs oxygen desolved in the water, but it is still breaking down water for more oxygen and therefore producing hydrogen
http://www.corrosionvci.com/Auto_Rust_Protection/r...

Edited by RizzoTheRat on Sunday 17th January 15:37

[Ferg]

Inhibitors quieten boilers by breaking the surface tension on the water to make it 'wetter'. This prevents the implosion of air bubbles on the uneven surface of the heat exchanger.
We used to use washing-up liquid, too.

[BigBen]

As luck would have it I drilled through a heating pipe today so had occasion to have a plumber round.

He pointed out that in a sealed system such as mine after bleeding radiators you have to refill the system to keep the pressure up, which I have not been doing, so now the pipe is fixed I will see how I get on

Ben

[dirkgently]

Gingerbread Man said:

Ferg said:

Sludge creating hydrogen.

This was one of my thoughts, when next bleeding it, see if it lights with a match.

If you do this, remember that a hydrogen flame is invisible to the eye,and you may set light to the curtains.

[Ferg]

LOL!

[King Herald]

Simpo Two said:

King Herald said:

It could be gas caused by continual corrosion, ferrous oxide, so some inhibitor might help, and might stop your rads rusting through.

Ferrous oxide is a solid - aka rust. Ferg mentioned hydrogen; I was trying to think of the chemistry behind it - what acid might you encounter that would generate hydrogen from copper or rust?

But as squicky says, easy enough to test!

Ferrous oxidisation = electrolysis = gas.