Single Pipe System makes noise

[cydodimead]

I have a single pipe system (think that is what it is called, HW and CH come on together) in my flat which is making noise. There are 5 radiators on the system, one of those being a towel rail. The towel rail is the only one with a bleed valve at the top. There is a strange semi knocking/air gushing noise in the bedroom just before the radiator which echos in the rad itself. This has a drain valve at the bottom. All the radiators are hot including the bedroom one but the knocking only happens when the system is first on. I have tried pushing the air back in the boiler by connecting the cold mains pressure to the hot tap (used the connections on my washing machine). I am 99% sure it is an air lock but how do I get rid of it? Boiler is a Potterton Flamingo 20-30

Thanks in advance

Cy

 

[cydodimead]

After reading //www.diynot.com/forums/viewtopic.php?t=4631&highlight=A I have found there are bleed valves on the radiators, very very very discreet

 

[JohnD]

If you have air in the system, you wil usually find that at least one of the rads feels colder at the top (where there is no hot water) than it does in the middle or bottom. Have you got a bleeding key to let the air out of the bleeding radiators?

When you do bleed then, observe what colour the water is that comes out, and if it stains your rag (or carpet, if you don't use a rag).



If it's a Flamingo, I presume you have a little header tank (feed and expansion tank) somewhere, high in the airing cupboard, perhaps, if you haven't got a loft?

 

[cydodimead]

Just been around all the radiators and bleed them. All the water is clear but strangley the radiator in the living room is hotter at the top than the bottom. Now that I have bleed it a bit it is very luke warm at top and almost cold at bottom

 

[JohnD]

With luck that will be a balancing problem. If there was no black or brown staining then hopefully it will not be a sediment blockage.

Turn the other rads down a bit, to force more pressure round the cooler one, especially if it is furthest from the pump.

Search on "balance," or look at http://www.diydata.com/projects/centralheating/balancing/balancing.htm

 

[cydodimead]

Would that account for the noise of "rushing gas sort of thing" in the bedroom. Will try the balancing tomorrow

 

[JohnD]

Probably not. Did you get much air out? Have you got a feed & expansion tank?

 

[cydodimead]

No air at all. By Feed and expansion tank do you mean small tank and big cold water one?

 

[JohnD]

F&E tank is usually about 1 foot high, 1 foot wide, 18 inches long. Will have a ball float valve inside like in a toilet cistern, will have a largish pipe above it, bent over so any water emerging will fall back into the tank.

If you have one, see if there is (1) water inside it (2) any sludge at the botttom (3) if you press the ball float down for a moment, does additional water flow into it.

The noise you were describing sounded like air to me, but if there is none in any of the rads, perhaps not.

 

[cydodimead]

Yes I have got a F & E tank and there is no sludge and additional water does flow. Started to balance the system this morning starting at the bedroom radiator and found the top to be colder than the bottom. I bleed the radiator (even though water came straight out yesterday) and there was a lot of air. After leaving it until all the air expelled no water followed. Whats next?

 

[JohnD]

I fear that the feed pipe from the F&E may have a blockage. This will prevent water going down to refill the radiators, keep them pressurised, and expel air or water from the bleed valves. One of the ways to test this is to put some extra water into your F&E so that it is filled above the normal water level by a couple of inches.

Then, any water travelling down to refill the rads will reduce this level.

If there is no blockage, then a pint of water (or air) bled out of a rad will result in a pint of water being drawn from the F&E.

If there is an obstructed flow, but the pipe is not completely blocked, then this may take hours or days. A blockage would prevent water going into your rads, and enable air to circulate in the system. Air (or gas) commonly arises as a result of corrosion in the radiators (which also makes the water black).

If you do have a blockage, it is unlikely to be shifted by chemical cleaners (because the blockage will prevent the chemical flowing round the pipes) but will need poking or cutting out.

As you have a Flamingo I would guess your system is 20 years or more old, so a blockage is not ususual.

Are you up to home plumbing repairs? If not you wil need to call in a pro.

 

[cydodimead]

I can't add any extra water to the F & E tank because it is just below the level of the overflow pipe. I don't think the radiators are at fault because they are only about 1 year old. The only old thing like you say is the boiler. I'm pretty good on DIY so plumbing repairs shouldn't be a problem. Currently trying something I read from another post which was to close the both valves on all the other radiators in the flat and then try and bleed the problem radiator. No joy as yet

 

[ChrisR]

Remove dud rad and attach hoses to unions, and hope to get flow. If not, check valves not stuck shut (see faq). Then you can try mains up the pipe to dislodge blockage.

 

[cydodimead]

OK radiator problem solved. Turned my system off and found lots of air came flooding out followed by clear water. Have left the system to cool down and then will start it up in a couple of hours to see if I gets the strange air whooshing noise in the pipe again.

 

[cydodimead]

Whoosing noise is still there!!!!!!!!! Going to drain the system and start over again. Any thing I should do different as my taps are on the same system as my radiators (Single system)?