Water hammer from tap

[Partingk]

A few months after fitting a twin lever ceramic disc type mixer tap to the kitchen sink now when any hot tap is run upstairs in the bathroom a huge vibration is set up in the hot side of the sink tap and the tap starts running. Holding the tap handle reduces this so it is obviously the disc that is the cause of this, reducing the pressure doesn't really help. the hot water is fed from a combi boiler but everything has worked fine for years before the tap was fitted

I cannot separate the tap mechanism to see if the disc has broken or anything, would you go for changing the tap or fitting an arrestor, there is no noise whenever the cold taps are run

 

[Mikefromlondon]

I am Not an expert on this, but since not one single expert has replied since you posted this, suddenly they will all be here like London Busses, 3 in a row going to the same place!

Water hammer is usually caused by a sudden closure of a tap, if your bathroom sink hot water tap is the cause of it, then I would be looking into that rather than your new kitchen taps, however, I am not ruling out a possible problem with your kitchen ceramic valve, that may have become far too soft and turns by itself under water hammer or pressure disturbance.

Does your bathroom use 1/4 turn ceramic taps as well, as these are the taps that close water flow more suddenly than multiturn rubber washer ones, your new kitchen leaver tap should not feel too soft to turn, if it does then the fault may be there for self opening and not being able to resist hammer forces. Even if the hammering is unavoidable, none of your taps should self turn.

but yes if you can't find the cause of your water hammer and cure the hammer problem, you may well have to use an arrester.

one way to isolate hammering is to close the bathroom taps slowly even if it is ceramic 1/4 turn type, close it very slowly, if this still causes a hammer problem then there must be another issue which could well be the boiler itself, what boiler is yours? some boilers use water pressure sensing to sense hot water demand request and a fault here could be the cause of water hammer.

Any way even if I am all wrong, at least I have helped bump this thread and if you wait a little while there will be a whole bandwagon of experts shedding their expertice just like the London Busses! (lol thats going to be some fun)

BTW, you also said that when you hold the kitchen tap leaver closed, the water still leaks, does this water leak only during hammering or does it drip all the time, if it drips then you may well need to change it as this leak indicates the two ceramic discs are not in 100% contact with one another through wear, although it is unusual it should have worn that soon, ceramic valves are or should be very long life, like 5 years, and there may be some debri that stops the valve from closing fully, so under a slight hammering it opens up.

 

[Partingk]

Thanks for the post, the bathroom taps are now 1/4 turn but it did it even with the old screw down, it also does it when the shower is run. There is a loud clonk when taps are closed and I guess this is the sudden stopping of the water flow caused by 1/4 turn taps as you say improved by slowly opening and closing the taps, do you think an arrester would help with this, if so would I just need to fit it on the cold mains after the stop tap? The screaming noise being made stops if the cold tap is also run with the hot tap. I am guessing there is some imbalance in pressure in the sink mixer when another hot tap is run as most combi's will only supply one tap at a time and the cold pressure is acting on the hot tap disc although this shouldn't happen if the water is only mixed on exit. I will keep at it and thanks for the help so far

 

[Mikefromlondon]

seems like your problem could also be pipes not being supported using clips etc, and cause pipes to flex when a water stops suddenly upon closing taps. This can aggravate your problem.

An arrester should be fitted as close to the source of tap that causes the problem,

think of water as a mass of some solid matter, if you propel a solid matter with some velocity, it will acquire momentum, and whenever anything that has acquired momentum, and when it is brought to a sudden halt, a lot of energy is dissipated, this energy can flex and bend pipes to a certain degree, and cause it to hammer and within the pipes water being liquid with mass, and is not compressable, so it must dissipate this energy somewhere and somehow, so the longer the pipe and higher the velocity, the higher will be the energy, so imagine if you were to put an arrester, it should be put at the far end of the long route, so that the momentum which continues to flow forward needs to be absorbed at the furthest point, so that being near the tap, though a few meters before wouldn't do any harm since water is flexible, it could dissipate this energy a few meters before the end of the pipe or where the tap is.

I would fit it on the hot water circuit as that is where you are getting your problems on, using compression joints, easily done, if it doesn't work, patch up the pipe and use it somewhere else, trial and error always works, it would be hard to work out theoretically unless you input every bit of information ina Cray Super computer to work out exactly where it should be placed precisely! ( )

Good luck mate, and see if any pipes that are not properly supported or fastened to walls or floor joists are done so so as to avoid moment as the enrgy dissipates pipes and joints bear the brunt of it. Securing them to walls and other surfaces help and stop pipes moving during the energy surge.

Looks like London Busses are on strike!!

 

[Partingk]

Thanks, what you say makes a lot of sense

 

[Nigel_Cro]

Just to echo what has been said above.

When we first moved in we used to get a lot of the 'clonking' noise you describe. Over a period of months I started lifting floorboards and adding pipe clips at various places and gradually managed to reduce the 'clonking' so that eventually everything was at peace...

It took a while, because stopping the 'clonk' in one place sometimes moved it to another place, and sometimes rather than making it better, made it worse!!

Concentrate on long runs and right angle bends.

Good luck.

 

[foxhole]

http://en.wikipedia.org/wiki/Water_hammer
Requires a reduction in water pressure not sure how you could have reduced your pressure to test this unless you have a pressure reducing valve.?

 

[jamie86]

I have had a similar issue before and the solution was an arrester, just to lend some support to what others have said here!

 

[jamie86]

Echoing the other replies. Arrester is the usual fix here!