I don't want to pester, but has anyone got an idea about...
The hot water tap in our downstairs loo has been recently replaced by one of those quarter turn jobbies. Now it is noticeable that, when you turn the tap off quickly (something that we couldn't do with the multiple turn taps), then there is a banging pipe sound; just for a second. The hot water comes from an upstairs cylinder fed from a loft header tank.Anyone got any suggestions for a remedy? Ta.
Up with the floorboards and find out what's banging, I reckon. That's what I had to do anyway :(
Si
Turn the tap off more slowly?
:-) That's what I do, but I have to train the rest of the family. Talk about teaching an old dog new tricks.
Seriously though, I think this is 'water hammer' and you might find an appropriate solution by googling for this term.
Is it possible that you have a "dead end" or a tap you have not yet bleed the air out of after having the downstairs loo tap replaced ?
If there is air trapped in a pipe somewhere, when you suddenly close the tap you will get a bang as a result of the air in the pipe acting like a spring and "vibrating" the column of water in the pipe (as the air is compressable).
If this is not the case, you probably have a loose pipe, which is banging a floor board or another pipe somewhere, all you can do is trace the pipe all the way to the tank adding extra clips, or trapping wads of rockwool between the pipe and the floorboards as required.
Good luck,
Paul.
Thanks for the replies guys. I don't think it's trapped air, so it must be 'water hammer'. Actually the washing machine also causes the same pipe knocking. It's on the same run of pipe so that's not too surprising.
In article , Graeme writes
Were you the guy who had a run of 15mm which joined an old section of
22mm before reaching the taps & washing machine? If so, this kind of transition is a classic discontinuity for the a shock wave to hit & cause a pipe shaking noise. When I changed a hot water run of 22mm to 15mm to improve warmup time I experienced this as I had left a couple of meters of 22mm near the taps. Suggestion is replumb the stub in 15mm, bolt down the pipes or add a water hammer (aka shock) arrestor - my least favoured option.HTH
You'll never eliminate the noise just by securing pipes, as the noise just couples to whatever you secure them too. The noise is the result of water flow not being able to stop instantly due to its momentum. I used an approach that I saw on 'This Old House'* to get rid of clonking noises. When I replumbed the kitchen (which is all at mains pressure, so clonking pipes was an issue before) during an 'upgrade', I added a vertical length of capped pipe fixed to the wall at each point where water is drawn (i.e at the sink tap hot & cold feeds, dishwasher w'machine etc.). The idea is that air is trapped and compressed in the vertical pipe when the system is first filled. This air then acts as a shock-absorber to the momentum of the water when the tap is suddenly shut. It works really well.
Nick
In article , NickIniquity writes
It's a nice idea, but it think the air will eventually be reabsorbed on at least the hot water run. Tried it to diagnose a flow instability in my CH circuit and kept finding my vertical spur full of water (after a few days). Water was much hotter than normal hot flow of course, but stub now replaced with a shock arrestor which has a has a diaphragm.
No. But comments read with interest.
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