Having to bleed radiators regularly

[Martin Harran]

Two of my radiators have to be bled about every two weeks, the rest are fine. I can't figure out how the air is getting into them. Any suggestions?

[.]

it isn't air, it's hydrogen and it's being produced because you don't have any inhibitor in the system. drain the system, add a propretory system cleaner, leave it in for a few weeks, drain the system and refill after dosing the system with an inhibitor.

[Andrew Gabriel]

What type of system: vented (small tank in the loft for it), or sealed (pressure guage and filling loop, usually in or near the boiler)?

[Bill]

In message , . writes

Wow, that is marvellous. How do you manage to rule out air and deduce all of that from the info given by the OP?

[Roger Mills]

That's a very definite 'diagnosis' - based on very little information, and a lot of assumptions!

It *may* be hydrogen - it may not. How do you *know* that there's no inhibitor in the system?

To the OP: You need to tell us a bit more about the system - whether it's sealed (pressurised) or vented and, if vented, whether there's any evidence of pumping over.

Next time you have to bleed a radiator, test for hydrogen by applying a lighted taper to the gas which comes out. It it burns with a blue flame, it's hydrogen.

[Martin Harran]

Vented, there's no obvious signs of the system boiling over into the venting tank - i.e. I never hear it doing so but maybe I shlod go up into the loft and have a look when the heating is on..

[.]

experience ?

[Peter]

Any boiling normally vents into your cold water tank. So if you haven't recently flushed the toilet with warm water you probably are not overheating. (Besides the rads would be uncommonly hot)

I once lived in a house where one upstairs rad needed total bleeding once a week and was told that this was because (the right words will fail me here) the air pressure valve was located too close to the pump/ or was it too close to where the pipes split to go upstairs. Also this was a rad that would heat by hot water or by c/h (ie bathroom rad) and no other rad ever needed bleeding.

Peter

[Roger Mills]

Eh?

[VisionSet]

Agreed, I don't have any inhibitor and I never have to bleed except when the system is refilled where I have to bleed all season long, but after that not at all. Conclusion: It's air! There is an awful lot of it in fresh water. And it takes along time of continual heat/cool to get it all out.

-- Mike W

[Mr Fixit]

exactly Eh I don't know of a system where the toilet is connected to either tank in the loft let alone the expansion tank for the heating system

[Andrew Gabriel]

Filling the toilet from the cold water storage tank is not uncommon, although that's nothing to do with the central heating.

[mike]

[e-mail] (Andrew Gabriel) wrote in news:444136e7$0$661$ [e-mail]:

It is in Peter's house ;)

mike

[Peter]

Haha ... ok the hot water tank expansion overflow, overflowed into the cold water storage tank, so that when the immersion thermo failed the water boiled into the cold tank and the toilet got a good umm cleaning. Having said that, its somewhat divorced from the OP's problem I now realise. (mental note... must learn to read)

Peter