We did a bathroom remodel a couple of years ago. At the time the
contractor had a problem with a knocking in the shower wall behind the
shower valve whenever any other water faucet was closed. A call to the
valve manufacturer did the trick. They sent out a new spool valve for
the shower valve assembly. It stopped the knock for about 2 years.
Then all of a sudden it started again. I took the shower valve apart
and couldn't see anything wrong with the spool valve. If I remove the
sliding piston from the spool valve the problem goes away.
Unfortunately I don't know what the brand name for the shower valve is
and we can't find the paperwork that came with it. It was purchased
from Expo Design Center but they can't help either. The spool valve
resembles a valve assembly from an automatic transmission. Can anybody
help me figure this one out? Thanks, Ray.
What kind of hammereing noise? There are two types I have experience with.
#1 Short burst of noise when faucets are turned off.
- The problem here is usually that when the valve is turned off quickly
the water's inertia wants to keep going but has no where to go so you get a
hammer noise that reverberates through the pipes. I have seen this in some
homes where for example a bathroom reno has been done and the tub/shower
valve has been replaced. SOme inexperienced plumbers see a chunk of 3/4" or
1" copper pipe going nowhere teed off from the water lines going to the
valve and figure it serves no purpose and remove it. Thats when the
The chunk of larger pipe is called a field fabricated water hammer arrester.
It is about 18" long and made of pipe at least 1 size larger than the supply
pipe, and is usually on the highest water supplied fixture on both hot and
cold lines. The job these arresters have is to be filled with air, and
thereby provide a shock absorber for the water. If there already is these
pipes still intact, then you might try draining the system down completely
and refilling it again. the arresters may have become water logged.
If you don't have them anymore, then you can also get a different style that
goes inline with the shutoff valves under a sink and are relateively easy to
#2 Long drawn out rattle or hum that stays until another faucet is turned on
-This problem is cause by one of two things. A leaking hosebib seal,
and a leaking toilet fill valve.
Check your hose bib, if it is dripping a little bit and doesn't stop,
replace the seal. and it should solve the problem.
If none of the hosebibs are leaking, thne check the toilets. Its pretty
easy to determine which toilet if you have more than one. Simply shut the
valve of for the toilet supply. Wait a while to see if the noise happens
again when you use water, if not then chances are thats the toilet. Simply
replace the fill valve(ball cock) and problem solved. For the price of the
fill valves, you may even want to just replace all of them in the house to
Hope this helps.
Canadian Red Seal Journeyman Plumber
BYRD Plumbing & Heating
Leon, thanks for trying to help. The noise I am getting is a knocking
coming from the shower valve and it usually knocks 8-10 times then
stops. I happens whenever a faucet anywhere in the house is opened and
then closed. It could be the auto lawn sprinklers turning off or a
toilet being flushed. We were rid of the noise for a long time then it
came back. I took the valve apart yesterday and found that it had what
I would call a spool valve screwed into the front of the main valve
assembly. Inside of that spool housing is a piston that slides back
and forth. The outer housing of the spool valve has four o-rings that
seem to separate the different chambers of the valve. When the piston
slides in or out it opens/closes the different chambers. When I
removed the piston the knocking stopped. I did notice that the four o-
rings appear to be hard and have shrunk to some degree. I was going to
replace them but found that I didn't have the right size in my box of
junk. I don't know if it will hurt anything by using the valve without
the piston in it. I assume it will just negate the anti-scald feature.
Is that correct? I can't see that there is any problem with the spool
valve as the piston moves freely. I have a feeling that maybe if I
replaced the four o-rings maybe it will stop the knocking. That's my
next move. If I could only figure out the brand of the valve assembly
it would sure help. I tried to find pictures of just the valve portion
online but everything I found was the outer decorative part. Thanks
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.