Running water sound in CH pipes after radiator valve change

30 Nov 2005
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United Kingdom
We have a system/conventional boiler (Viessmann Vitedens 100W) with a feeder tank in the loft.

A leaking radiator valve upstairs was changed, which involved draining quite a bit of water from the system. After fitting the valve, the engineer refilled the system and mentioned we may need to bleed any radiators.

Since then we have had a constant loud running water sound in the airing cupboard when the heating/DHW is on. There are no leaks anywhere, the sound is inside the pipes. I have bled the radiators and there is no air coming out of them, though one downstairs radiator remains cold, which combined with the running water sound suggests there may be air stuck in the system?

Reading on here and elsewhere, I have also tried letting air out of the valve above the DHW tank in the airing cupboard, though just water came out. There is still plenty of water in the feeder tank in the loft. Is there anywhere else to bleed air from?

Do you have further ideas how else to get air out of the system please, to get the final radiator working and stop this incessant running water sound?

Thank you
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Close the TRV ( thermostatic radiator valve ) on all rads that heat up ,don't touch their lockshield valves) and see if cold rad now heats up.
When it heats up ,bleed all rads and see if situation is any better.
Thank you - that has got all radiators now working, there was no air coming out of any radiators, but still the running water sound in the airing cupboard.
I have been in the loft and the water tank has water in (above the out/lowest pipe, but way below the inlet attached to the ball valve - the only other pipe attached is the overflow). Oddly no water comes out of the ball valve/inlet when the ball valve is down, but there is plenty of water in the tank. Could it be filling up from somewhere else on the system? The engineer did say the pressure on the radiator didn't really drop when putting bungs(?) in the tank, so had to switch off mains water before changing the valve.

We also have a metal balloon type that seems to be above the shower (it is Varem and says "Max Press 6 bar" on the label) - it has a tyre type valve for attaching a pump? Is that related to the heating or shower and would that affect the issue I am having?

You can tell I am just a householder, sorry if these are silly questions.
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Show us some pics of what you described above the shower, together with your hot water cylinder and pipework around it.
How did engineer fill the system back up ?
I seem to have solved the running water sound. I didn't realise that the top right could also be turned to release air (I had just turned the small one in the middle).


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Feeder tank level has dropped slightly which suggests it has taken water in. No running water into the tank though, so it may be the ball valve needs replacing (engineer mentioned it may need doing at some point soon, but must have somehow got water running into it to top up the system).


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This was the metal balloon with max 6 bar indicated on the label.


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That's an expansion vessel for domestic hot water.
If the ballcock is not allowing water into the tank when you press down on it ,you need to investigate why,and fix the issue. It's either isolated ,or blocked or needs replacing.
Thank you. It was your suggestion to take photos that prompted me to take a closer look at all the pipework above the hot water cylinder. While at eye level to take the photo I then spotted the top of the other big valve could unscrew to let air out.
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1. If the "small one in the middle" which you turned (your 1st photograph) is the one with the black plastic top half, that may well be an automatic bypass valve.
2. The auto bypass lets hot water pass directly from flow to return when all valves are closed, to save damage to the pump.
3. If you have altered the setting you might have to reset it. There are various videos on how to do this available on the internet.
No, sorry, I uploaded the wrong photo - the middle valve is small and bronze (not in the picture). I didn't touch any of those with plastic caps as they didn't look like they should be removed.

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