Air in Radiators

[mikedry]

Hi

First time posting on a subject I do not know much about so please be patient!

I have air in my radiators. If the heating is on all day then the living room radiator fills with alot of air.

The setup is as follows:-

I have an oil fired boiler which has 2 pipes going into the hot water tank and 2 which supply the central heating. (6 radiators)

I have a tank in the loft which seems to only supply water to the hot water cylinder. I cannot see any pipes supplying the cntral heating?

There are no leaks at the pipes coming from the boiler but I have not managed to check all the pipes under the floor yet.

The tank in the loft seems to use water all the time with a steady flow coming out of it into the hot water cylinder indicating a leak somewhere.
When I bleed the radiators the water comes out black.

What I am looking to find out is the cause of the air but also that if air is bled from the system then does water replace it and where does this water come from as I said there seems to be no connection of water to the central heating system.

Want to at least try and find out as much as I can before going to the expense of calling someone out.

Many Thanks
Mike

 

[glasgowgas]

I have a tank in the loft which seems to only supply water to the hot water cylinder. I cannot see any pipes supplying the cntral heating?

primatic cylinder perhaps

 

[Boilerman2]

as you are bleeding off a lot of Black sludge, the air could be hydrogen gas, caused by electrolytic reaction between copper, brass and steel within your system, you say you can't find a 2nd small header tank anywhere?, it is unlikely that you have a sealed system, as it would have run dry by now with all that bleeding, I am going to guess that you have a "Primatic" Cylinder, which separates the primary and secondary water by way of an air bubble within the cylinder, effectively you can't add inhibitor to this sort of system, which would reduce corrosion and build up of hydrogen (air), I would suggest getting a Heating engineer in to have a look, it sounds like money will have to be spent to resolve this problem
Best of luck!!

 

[kevplumb]

View media item 15179
heres one i sawed earlier

 

[mikedry]

Hi

Thanks for that. It answers alot of questions.

Can you in laymans terms explain exactly how a primatic cylinder works. I want to be armed with as much info as poss.

Many Thanks

 

[Nige F]

water comes in thru` pipe on left. Strange thing with domes/ air bubbles goes to boiler . small pipe that`s white is an airlock /vent . That`s all I`ve got time for . Took me long enough to work it out myself when apprenticed

 

[mikedry]

The plot thickens. I was beginning to loose alot of water from the expansion tank which pointed to a leak.
Took up some floorboards and found a nice puddle of water under the floor.

I have discovered that when we had some damproofing carried out 8 years ago the company laid in concrete to hold the DPC down.

They have in some parts laid it under the pipes, in some parts there is a covering on the pipes and in other parts they have completely burried the pipes. The part where the leak is is burried under at least an inch of concrete which I think has put the pressure on the pipe thus causing the leak although I have no absolute proof.

Has anyone heard of this before and any idea on the comeback I may have against the wood preservation people? Is it common practice to lay this concrete on top of heating pipes? I will be phoning them tommorrow to get their view on it!

Of course my other worry is that other pipes may be leaking or in the future may leak.

Many Thanks

 

[SuperMario80]

Hi, any copper pipes laid in concrete should be WELL protected. The concrete will slowly but surely corrode the pipe. Pipes should be thoroughly wrapped in some sort of lagging before buried in concrete.