Anyone got any advice, I have recently added 6 new rooms to my house and have extended the radiator circuit to suit. All is working well apart from one radiator in the second bathroom. radiator is 400 * 600 and is constantly giving problems with air having to be bled from it. Every about 4 days the radiators output is noticibly reuduced by a small amount of air being in it. Once bled normal service is resumed. Cannot spot any obvious leaks although the end stops are the type with the rubber "o" ring on them which does have a kind of greasy feel to it like it could be weeping slightly any advice/ stuff I can add to the system to search out leaks. System is conventional boiler with header tanks on radiator circuit.

Thanks

Graham

Graham - I'm no heating engineer but when I drained my whole system last year (refitting bathroom. cloakroom, coupl of rads etc) I spent approx 4-6 weeks bleeding the rads before the air was finally gone from the system. I think it just takes time to get rid of all the air pockets. There's probably another more scientific way of bleeding to clear the air quicker but, as I said, I'm no heating engineer :)

Cheers.

Alex

Calling Mog where are you as I have the same Problem


It's driving me mad

I think that if your pump is too fast (high flow rate) then air can be sucked in through leaks that are too small for water to get out of!

Are the rubber stoppers "telescopic joints" to allow for slightly different sized radiators to be fitted (as i also have these). The "grease" could just be petroleum jelly used to lubricate them.

mb

Is it a build up of air, could it be Hydrogen? Try lighting the air/gas next time you bleed the system.
Does your system have corrosion inhibitor added? A lack of corrosion inhibitor can cause a build up of Hydrogen as the system corrodes.

Kevin.

[Edited by Kevin Groat - 1/3/2004 8:39:44 AM]

Have you put some fernox or other treatment in the water? Hydrogen can be produced through some process (electrolysis???) so that's worth checking - fill a small container with the gas and see if it lights with a squeaky pop. Remember your chemistry lessons? ;)

Air can move around a system, but it shouldn't take an age...

Hopefully one of the engineers will see this and post...

No Fernox in the system as wanted to get rid of the problem before putting it in but perhaps that is the cause of the problem in the first place. Will try the hydrogen test, do remember the chemistry lesson although the amount of air that is in the Rad may be hard to capture enough. But wonder why it only seems to collect in one radiator, perhaps this is slightly higher than the rest of the radiators in the system. May even try to swap the radiator with one of the other that are the same size to see if the problem stays or moves, if it moves then can be safe to assume that the radiator is drawing in air. Hopefully one of the real plumbers will turn up soon!

The first thing to do is as is said above, test the 'air' to see if it is infact hydrogen.

If it is air, it could be the pump set too fast. Air is NOT drawn in through small leaks, it CAN be drawn in through the open vent pipe (the one which hooks over the top of the filling tank) - if the system is not designed correctly. This all depends on what type of system you have, if you dont have any filling tanks, you most probably have a 'sealed system' which you fill by a temporary filling loop (small length of braided hose with valves at either end).

If it is hydrogen, did you thoroughly flush out the entire system after you added the new radiators?
When you solder central heating pipes you also use flux to prevent oxidisation of the copper whilst soldering. Most modern fluxes are 'self cleaning' types and highly corrosive. They need very thorough flushing after any work has been done, not doing it will almost guarantee problems.

All air/hydrogen problems I have ever come across have always been down to incorrect system design/installation or contaminated water in the system. Adding an inhibitor (Fernox, Sentinel X100, Salamander, etc) can sometimes hide the problem for a while but will take more work to actually cure properly.

Hope this helps
Andy



[Edited by NewAgeWRX - 1/4/2004 5:09:25 PM]

Ok Andy will have a go at the hydrogen test. System does have a vent pipe that is over the top of the header tank in the loft. I have turned the pump down to the slowest setting tonight to see how we get on there. Last bled the radiator about 5 days ago and is still performing ok so cannot do the hydrogen test quite yet. Will order so Fernox to give that a try. System has been well flushed and currently has sludge remover in it that I will drain out during the week. Prior to adding the 6 extra radiators I never had a problem with the system so hopefully not to much of a problem. Failing a cure it looks like I will have to resort to bleeding the offending radiator once a week!

I have this problem too - turned down the pump speed and it hselped a lot. Made the whole system quieter too.

I have been having the same problem myself recently. Seem to be bleeding the radiators all the time.

This only seems to be the case when I have the hot water heating on though. When its just the central heating it isnt half as bad. All sorts of gurgling and swooshing of water noises can be heard from the loft at times.

Will try turning down the pump speed.

Daft question i know but are you lot turning your heating off and bleeding the radiators when there cold? cos if your doing them when the heatings on/radiators warm then they will naturally drag air back into the system.
Ive found many people dont realise this :)

Definitely check this - when the pump is running you can actually get negative pressure in some rads, and when you think you're bleeding them and hearing the tell-tale hiss, that's actually air being sucked in through the bleed valve.

Right X100 is now in the system. Bled on Sunday night air in 2 rads on Monday. Bled again last night see how it goes. Must admit was doing while heating was hot but pump off so will see how it goes if not will try when cold!

The rad I have that does this is a chrome towel rail jobby. 1st posted about ages ago. Was sceptical about the hydrogen thing but got a nice shoot of flame when I tested it. Its still doing it (this was early last year I guees). Down to ****ty cheap rad with crap in the bottom I believe.

I bleed it with the hetaing on and you can fell the water (heat) level rising up the rad and eventually you're rewarded with a very hot jet of water ;) - defo no negative pressure there!

Deano

Oh dear dont think it is Hydrogen as still getting air in the one radiator! Will give a couple of more days of bleeding but not looking good. Looks like could be drawing in air from the expansion pipe. Is there any way of confirmfing / ruling this out. Done a bit of internet trawling and there is something called an AirSep made by tower are these any good for getting rid of the problem?

There is one very good way to test for air been drawn in through the OPEN VENT pipe (often incorrectly called expansion pipe).

Best thing to use is a milk bottle. Turn your heating off - doesnt matter whether it is hot or cold. Fill the bottle with water and go up to the loft. Dip the end of the open vent pipe into the full milk bottle and get a m8 to turn your heating on. If your system is pulling air in the water in the bottle will be sucked out of the bottle and down the open vent pipe!!!

I must say, it would be unusual for your system to not do this before the rads were added and do it after.

There are a few other possibilities. Another thing that can cause hydrogen in rads is bacterial infestation (LOL this sounds bad but I had this in MY OWN system after I flushed it out). When you introduce fresh water to a system bacteria can be carried in too. The bacteria multiply and give of gasses. One way to tell is to try to smell the gas that you are venting from the rad. Ofcourse this is a non-scientific way but most often if it is infested water the gas will smell VERY bad (hydrogen does not have any smell at all).

Did you dose your system correctly? Usually a single litre bottle of X100 will treat up to 10 rads. If you have more, or have a system that incorperates a thermal store you may not have put enough in.

In my earlier post is mad a sweeping statement saying 'air is not draw in through leaks' - maybe I ought to correct/expand on this. On a correctly designed system (Where the vast majority of the system is under positive pump pressure) air is not drawn in through leaks. On an incorrecly designed system (open vent and feed pipe right after the pump - dont laugh it happens) air CAN be drawn in through leaks as most of the system is under negative pump pressure.

Andy

Nice one Andy, will try the "milk bottle" test over the weekend.Just hope I havent got a leak anyway as have now plasterboarded all ceilings and put all the floor down everywhere. Did test the system for a few days prior to sealing access up by who knows. Next logical question I suppose is there anyway to test for small leaks. I did work or part of the system recently by plugging the vent pipe and the inlet in the header and that held the water back while I worked on it, suppose if I did have a leak this would not have worked. But then again is the leak was a real small weep then I suppose it would have been alright. Thanks for your input again!

Hobbsy...the fact that the system was ok before and that you have a air seperator then the cold feed/vent pipework is probably not the problem.
What I would suggest is that the "air" problem is from a chemical reaction to the new radiators and pipework which have been added to your existing system. All the new pipework will have a considerable amount of flux in it and the radiators will have steel swarf, mineral oils and thread cutting oil left in them from the manufacturing process...when all this is heated up with your existing system the result is a very corrosive solution producing air/gas.
Seeing as you have added 6 radiators then will need at least 2lts of Sentinel X300 to clean the system and then 2lts of X100 inhibitor. Only when this has been done should you be looking further afield for other faults.

Mog