Water Hammer Problem

full-time-mum

I'm not very DIY orientated and would really appreciate some information/advice.

We have suddenly noticed a huge water hammer problem. It occurs if the toilet in the guest bedroom bathroom is flushed at the same time as some other major use of water is occurring - flushing another loo, using the shower, the washing machine filling up etc.

A weekend or so ago, by BIL took out the old dishwasher. During this process, he had to turn off the water. This may or may not be relevant to the problem.
We have only noticed the problem since then but, as it is the guest bathroom, it is possible, although I feel unlikely, that it was there before and we just never encountered the set of conditions.

Could someone please explain a bit about the mechanics of the water hammer effect so I can see if I can fix the problem without having to resort to a plumber.

The pipes are vibrating and it is echoing around the house. I think the origin of the noise is in the toilet cysten as the whole casing vibrates, as does the floor where the pipes flow - very strange if you happen to be standing on that bit of floor.

Is it that the water pressure is too high/too low or is there some other cause.

Thanks

djheath

If your BIL turned the water off then when he turned the water back on, he may have turned it on too much, causing an increase in flow rate. Try turning the stop !!!! down a little and see if it helps.

Other ideas could be to get at the vibrating pipes and secure them to stop them vibrating.

robnye

almost certainly caused by the mains pressure being turned back up to high.... we had the same problem.... turned the pressure down.... still have it intermittantly if too many things drawing water at the same time, but can live with that

davetrousers

BTW this site censor the use of the word c0ck! so you have to use a 0 instead of an o.

I also reckon it may be due to the water being turned off at the c0ck and when turned back on it was opened more than it was before. Would be the first thing to check, throttle it back a bit and see if that helps.

ormus

yes agreed. almost certainly caused by opening the valve too far. turn it back a bit and is should be ok. trial and error really.
pipes may need more pipe clips to secure the pipe/s but unlikely as you didnt have this prob before?

Canucklehead

Hi

Try changing the ballvalve washer in the cistern. Let us know what happens?

Corgi Guy.

full-time-mum

ormus wrote: »

yes agreed. almost certainly caused by opening the valve too far. turn it back a bit and is should be ok. trial and error really.
pipes may need more pipe clips to secure the pipe/s but unlikely as you didnt have this prob before?

I've tried turning it down and it if I turn it down too low then the cysten vibrates in its own right without flushing another toilet or turning on the shower. Seems to imply the opposite is true. Trouble is, if I open the stopcock too far, it leaks. :mad:

Canucklehead

Trouble is, if I open the stopcock too far, it leaks.

Tighten the small nut where the spindle ends.http://www.screwfix.com/prods/15940/Plumbing/Brassware/Stop-!!!!-15mm


Corgi Guy.

reheat

full-time-mum wrote: »

I've tried turning it down and it if I turn it down too low then the cysten vibrates in its own right without flushing another toilet or turning on the shower. Seems to imply the opposite is true. Trouble is, if I open the stopcock too far, it leaks. :mad:

Was it the main stopcock you turned down, or just the one to the loo cistern? The trouble with water hammer is the sound can carry through the whole water system and sound like it's originating from places it's not. It may be the real culprit is the ballvalve in the main water tank, and it sounds like it's somewhere else - the whole water system hammers once it gets going. It's very possible the main stopcock to the house (usually under the sink) is turned up a bit too high ... as others have said here. Must admit it's confusing you say it gets worse when you turn the water pressure down, which is why I'm wondering if it's the right one you are turning down?

Water hammer occurs when a ballvalve bounces up and down in the water at the same frequency as the water pressure rises and falls in the pipes. The ball valve bounces up in the water closing off the valve, the pressure rises in the pipework pushing the ballvalve back down a tiny bit, the pressure falls off and the valve comes up again, and round it all goes again and again. When both are happening in sympathy you get positive feedback ... same basic mechanism as sound systems screeching and the way suspension bridges have shaken themselves to pieces! One trick is to do something with the ballvalve (edit: sorry, I mistakenly said stopcock earlier!) to damp it's movement a bit, but could be a bit risky trying if you're not plumbing inclined. The easier thing is usually to reduce the water pressure, so there's not enough power to keep it oscillating.

Canucklehead

Water hammer occurs when a ballvalve bounces up and down in the water at the same frequency as the water pressure rises and falls in the pipes. The ball valve bounces up in the water closing off the valve, the pressure rises in the pipework pushing the ballvalve back down a tiny bit, the pressure falls off and the valve comes up again, and round it all goes again and again. When both are happening in sympathy you get positive feedback ... same basic mechanism as sound systems screeching and the way suspension bridges have shaken themselves to pieces! One trick is to do something with the ballvalve to damp it's movement a bit, but could be a bit risky trying if you're not plumbing inclined. The easier thing is usually to reduce the water pressure, so there's not enough power to keep it oscillating.

If you get this on the main storage tank, replace the 4" float with a 6" float on the ballvalve.(It just unscrews) Adjusting the stopcock is not the answer.

Corgi Guy.

reheat

Canucklehead wrote: »

If you get this on the main storage tank, replace the 4" float with a 6" float on the ballvalve.(I just unscrews) Adjusting the stopcock is not the answer.

Corgi Guy.

Ah ha ... neat idea!