Take the 2-minute tour ×
Home Improvement Stack Exchange is a question and answer site for contractors and serious DIYers. It's 100% free, no registration required.

When I shut off a water faucet or right after the toilet tank refills after flushing, I hear a vibrating sound in my pipes. It last between one and two seconds.

On the interwebs, I found out that it's called "water hammer" and that it can be fixed by draining my plumbing system: by shutting off the water main and opening up all the faucets and flushing all the toilets in the house.

Well, I did that and it helped for two, maybe three days. What do I do next (other than call a professional)?

share|improve this question
    
How long did you wait after you drained it before you turned the water back on? –  Dennis Williamson Sep 12 '10 at 21:00
    
20 - 30 minutes –  vitule Sep 12 '10 at 21:01
4  
My guess is that draining the lines in your house introduces some air into the system. That air softens the water hammer, acting as a cushion. After a few days the air is gone, so your water hammer is back. The water hammer arrestors work by providing that cushion on a permanent basis. –  user558 Sep 13 '10 at 2:00
add comment

4 Answers

I had this problem. My pipes started making a very loud banging. I tried the drain the lines trick but it didn't help. I then put a water pressure gauge on my faucet and found my water pressure to be up over 100psi. I followed the steps for reducing the water pressure on the water pressure reducing value but then noticed that after running the water for just a few seconds the pressure dropped to almost nothing. I then replaced the water pressure reducing valve, which in my case was faster to actually replace then it was to go buy. Now I have no banging and constant pressure. Moral of the story, go buy a $10 water pressure gauge and make sure your pressure isn't high. I can't believe with my luck the pipes didn't break.

share|improve this answer
add comment

I had water hammer in bathroom commode. Removed top and adjusted the screw to allow more water inside tank before float shut off water value. Hammer sound stopped and tank filled quicker.

share|improve this answer
add comment

@Mike Powell, That's a great answer if it is actually water hammer. If it turns out to be the toilet valve that is causing the vibration then the valve will need to be replaced. Take the lid off the toilet, then push down on the float until the water starts to fill the tank. Then let go of the float. Do you hear the vibration? Do you hear any form of noise coming from the valve itself? Or is the noise just in the pipes? For the valves that have a float extended on a long steel rod, this float can gradually close the valve while the tank fills and cause a whining noise as the valve closes. If there is loose piping in the walls, this flow "restriction" can case a vibration.

share|improve this answer
add comment

This normally happens near quick-acting valves in your plumbing system, like those used in a clothes washing machine. Those valves are opened by a solenoid and get slammed shut by water pressure, and all that water coming to such an abrupt stop can rattle already-loose pipes, cause them to become loose, or in the worst case damage them over time and cause leaks. That's why water hammer arrestors are commonly installed near washing machine outlets (it may be required by code, I'm not sure). They look like this:

water hammer arrestor

They work by maintaining a reservoir of air inside that vertical tube. When the column of water is stopped abruptly by a valve, the air acts as a cushion, compressing so that the water can slow down more gradually and impart less inertial force to your pipes.

These are fairly easy to install even for someone with no plumbing experience. I believe the one pictured is designed to be mounted inline with a sink or toilet connection, and they also make models with standard garden hose style threads for a washer connection. You shouldn't need to install these at every fixture; one set (hot and cold) for each bathroom/kitchen should be plenty.

Since your problem seems to occur on (relatively) slower-acting valves that shouldn't be generating an unacceptable amount of water hammer, you may also just have a section of pipe that's not mounted properly. If you're only noticing the banging sound in one area, it may be possible to open up the wall there and install some pipe clamps to keep things from moving around and making noise. This would be a more difficult job than installing arrestors (but potentially cheaper if you do it yourself).

share|improve this answer
2  
+1 Excellent answer! –  Doresoom Sep 13 '10 at 21:16
8  
Actually the valves in washing machines are opened by a solenoid valve. They are closed by a spring, and also by the water pressure itself. The more pressure, the faster these close, the more sound that is created. –  Brad Gilbert Sep 15 '10 at 16:00
    
@Brad Gilbert: good point, I'll edit my answer. –  Mike Powell Sep 15 '10 at 17:37
4  
I believe I saw This Old House do a DIY arrestor by just installing 12-18" of copper pipe on a T-fitting with a cap on the end. –  Freiheit Jul 11 '11 at 18:55
2  
The major problem with DIY arrestors is over time, the air will leak out and be replaced by water, and once they are filled with water you have two issues: the arrestor will effectively be useless, and it'll also be a dead-leg that can harbour bacteria which will then contaminate everything downstream (and possibly upstream, if the water sits unused for long enough). Actual arrestors have a piston inside that keeps the air contained. –  gregmac Sep 4 '13 at 20:39
show 1 more comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.