Recently the GF had significany rennovations done to her home. It
involved a new bathroom. The fixtures remained basically in the same
locations, but the plumbing had to be adjusted very slightly. New
taps, nozzles, etc. There were no signifant changes made that I
The issue is when she turns off the COLD water quickly there is a
thump-thump behind the shower wall, but it does not repeat itself. It
is difficult to tell, but it seems to come from above the faucet
assembly. The water feeds from below.
The same happens if the sink in this bath and the adjoining bath or
the toilet flow stops suddenly - it seems to be the cold water in all
I do not think it happens with hot water, nor does it happen if the
water is turned off more gradually.
Is there a possibility it could be the shower valve assembly, or a
loose pipe? I am hoping there is some way to try to repair it without
going through walls.
Any imput/observations/approaches to try/or further diagnostic methods
to narrow it down more would be greatly appreciated!!!!
That's classic water hammer. You can find lots of DIY web sites now
that you know the right name.
I would start by draining the pipes to recharge any existing hammer
chambers: Turn off the water at the meter, open all the faucets and let
the water drain for 30 minutes, close all the faucets, turn the water
back on at the meter. When you open each faucet thereafter, air will
come out for a few seconds.
On the other hand, tell the remodeler you have this problem. He should
fix it under warranty.
This good advice omits only the explanation.
Water hammer is shock in the water pipes (transmitted everywhere in
the system because water is incompressible.) The building code now
requires at least one shock absorber in every system, a vertical pipe,
capped at the top, and full of air. Shock in the pipes can push water
up into this pipe (because the air compresses). But in time the
vertical pipe can become full of water (waterlogged) thus has no
compressible air at the top to act as the shock absorber. The
solution is to drain the whole pipe system (not the tanks that
supply it) so that the vertical pipe empties and can resume
Thank you very much everyone. I will try that. I will shut the main
H2O off and totally drain by letting it all sit for a bit with all
faucets, etc open to see if that will help.....
IIRC, I did see a copper 'stand-off' at the top of each pipe in the
shower which I assume would be the air 'absorber' column you are
speaking of. (of course this was before all the ceramic tile was put
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.