How do I cure knocking cold water pipes ?

JBrennand · 20 Jan 2009

Apologies as this is a re-post from last year, but I haven't sorted the problem yet ! Every time we flush the upstairs or downstairs toilets there are 2-3 seconds of gdunking and thunking at the end of the cycle. This started after I had turned the water off at the internal stop to fix a leaking downstairs kitchen tap. I am assuming it means that there are air pockets in the pipe.

So, are there any standard procedures for curing this? Along the lines of.... switch the water off, open the highest tap in the house, turn water on, turn tap off ? Except that didn't seem to work ! Or is it drain the system by opening all taps and then switch water back on with all taps open and then close them lowest -> highest. Or something else?

Any help appreciated

John

Aquaheat · 20 Jan 2009

Doesn't sound like an air lock, sounds more like the pressure is a little high. Turn on the cold tap in the kitchen then turn down the internal stop tap a little so that you see a slight decrease in pressure at the tap. Try the cistern now and if the noise persists try it a little further. This should cure the fault.

bengasman · 20 Jan 2009

a better way would be to fit a new ball valve which is suited for the job and leave the stopcock fully open

Aquaheat · 20 Jan 2009

well yes there is that but wanted to prove that it was the ball valve at fault in the first instance for the OP and to give some eleviation to the noise until it could be replaced

buck51 · 20 Jan 2009

hi, as you said this started after you had turned the water off it is posibly air in the cold supply, do you have an f&e tank in your loft ?? If so the air could be up there, so drain a bit of water out of your heating system, untill you can hear if filling then try it again, if its still making the noise try changing the ballcocks as bengasman said, if that dont cure it fit more pipe clips. let us know how you get on

buck51 · 20 Jan 2009

Im sure I typed BALLCOCKS.If not then very sorry for typing error

Aquaheat · 20 Jan 2009

OP is on about a toilet cisterm buck51

buck51 · 20 Jan 2009

are you a plumber, I know what he posted and I know what im on about do you

JBrennand · 20 Jan 2009

jonjb said:
well yes there is that but wanted to prove that it was the ball valve at fault in the first instance for the OP and to give some eleviation to the noise until it could be replaced

Thanks Jon and others. Firstly I have a combi boiler so there are no hot or cold water tanks. Both toilets had their ball valves replaced a year or so ago with the plastic/silent types that have the trailing bits of plastic tubing. To be truthful they have always shut off with a "clank" - the British gas/Dynorod plumber said that was normal/typical of these ones. But it is now a more sustained clanking noise.

i'll play with the pressure at the weekend - but speaking from a position of (obvious) total ignorance it just "feels" like air in the system so i'll try a drain and refill as well.

Cheers

bengasman · 20 Jan 2009

JBrennand said:
but speaking from a position of (obvious) total ignorance it just "feels" like air in the system so i'll try a drain and refill as well.

Cheers

bad idea

JBrennand · 20 Jan 2009

bengasman said:
JBrennand said:

but speaking from a position of (obvious) total ignorance it just "feels" like air in the system so i'll try a drain and refill as well.

Cheers

Click to expand...

bad idea

How so ?

bengasman · 20 Jan 2009

would you change the oil if you had trouble changing gears?

it has nothing to do with your heating.

JBrennand · 20 Jan 2009

bengasman said:
would you change the oil if you had trouble changing gears?

it has nothing to do with your heating.

I guess I wasn't too clear - onto the 3d glass of wine is my excuse. I have no intention of going anywhere near the heating system. I meant to say that i will turn off the H20 and open all the cold taps in the house till it drains the cold water pipes and then turn the water back on - slowly.

If that don't fix it then I will get it sorted via my British Gas service cover.

Thanks for the comments

John

kirkgas · 21 Jan 2009

you do not get air trapped in mains water, too much pressure and/or loose pipework is causing the problem, and as it is a plumbing prob dont expect to get it fixed by BG

Slugbabydotcom · 21 Jan 2009

Sounds like you have torbeck valves. These always shut off with a clunk. Thats because they use mains pressure to close themselves off. When you buy them they have plastic spirals that look like Fusilli The finer of the spirals provided reduces the pressure and hence quietens the valve shutting noise. Clipping loose pipes and thermal insulation if appropriate will help dampen the noise.
If it still causes annoyance you could try partly closing the isolation valves to act as a pressure reducing valve or better still fit a pressure reducing valve.
DO NOT follow the advice given earlier by buck51 and bugger about with your heating system as this has nothing to do with your problem.
As you mention that you were doing other work before the problem started it might be worth trying cleaning the valves out first as some crud may have got into them. Take care though, they are tricky and I always manage to spike my finger on the pin.

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How do I cure knocking cold water pipes ?

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