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 <likearock@socal.rr.com> wrote in message news:1189470309.060998.16160@d55g2000hsg.googlegroups.com... > 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. >