Pressure balanced shower valve hammering


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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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 hammering begins.
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 install.
#2 Long drawn out rattle or hum that stays until another faucet is turned on again.
-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 be sure.
Hope this helps.
Leon Bourassa Canadian Red Seal Journeyman Plumber BYRD Plumbing & Heating

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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 again, Ray.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Check out Moentrol by Moen. If so call Moen, lifetime warrenty. You can operate it without the bal.spool but it won't be an anti scald so be careful, if someone flushes you'll know it.
kenny b
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.