View Full Version : Water hammer mystery / crisis
09-17-2005, 06:05 PM
Hi, after a few months of frustration I'm looking for any ideas to solve my water hammer problem.
I remodelled our upstairs bathroom about 4 months ago. Did the plumbing myself which was not particularly challenging...basically shifting a toilet slightly and moving a sink from one side of the room to the other (now beside the shower-tub). Without changing any of the fixtures, I suddenly started getting an extremely loud water hammer noise whenever the sink and shower are turned on/off. The banging is loudest near the shower faucet area.
I have tried (without success):
- replacing and lengthening the air chambers behind the sink and shower
- replacing the chambers with arresters (basic piston-type, from local hardware store)
- draining and refreshing the entire house system numerous times
- replacing the pressure balance valve in the Moen shower faucet
- replacing the cartridges in the sink faucet (8" Blanco model)
- securing the pipes against the studs
At this point I'm wonder if it's the actual piping layout (all 1/2" copper), or a pressure change caused by the sink and shower now being beside each other?
Suggestions welcome, thanks!
09-18-2005, 05:19 PM
this is a tough one. i,ve never done this, but read of it in plumbing a house by peter hemp[great book!]
make up a copper manifold ,same diameter as service ,usually 3/4 or 1"
using tees , make up 4 to 6 -18" risers with end caps. copper union at each end, and full port valve at each end. place this assembly inside house after pressure reducing valve. now in time, when they fill with water you can disconnect and dump water . good luck and get the book ,you won,t regret it
09-18-2005, 05:20 PM
Water hammer is caused by water stopping fast and the the inertia causing the pipe to continue moving. Usually, the only valve types that cause that kind of a problem are washing machines, dishwashers, icemakers, and toilet ball cocks. When does the banging occur? After you flush the toilet? If so, replace the ballcock - it's cheap. Let us know, and we can be more specific, and offer some other suggestions, if required.
09-19-2005, 09:05 AM
make up a copper manifold ,same diameter as service ,usually 3/4 or 1" using tees , make up 4 to 6 -18" risers with end caps
I thought that air chambers aren't used anymore. Is this a code and/or health issue? Old stagnant air w/ water would be trapped and grow all kinds of interesting things, no?
09-19-2005, 10:05 AM
In addition to being a dead end, arrestors are going to fill with water due to the air being absorbed into the water, and then you have to drain the system to get air back into the (air over water type) arrestors but.. The cause of water hammer is the velocity of the water in the pipe and shutting it off quickly. Adjust the pressure downward and you decrease velocity; add a pressure regulator valve and set it at say 50 psi and your hammer problem should disappear. With 1/2" plumbing, you may have to go below 50 psi. Of course this assumes you aren't hearing expansion of the plumbing against something and thinking that is water hammer.
Quality Water Associates
09-19-2005, 11:24 AM
Thanks for the comments. I'm pretty sure I've ruled out waterlogged air chambers and arresters. Even gone so far as to remove them and resolder them back on to make sure they're full of air, not water, when the system is refilled.
The noise happens in 3 ways:
-- sink faucet - on/off creates sharp bang, as does sudden flow change (like twisting handle quickly)
-- shower faucter - turn the tap off (single lever) creates loud banging noise that seems to echo or reverberate for a couple of seconds
-- toilet -- when the tank finishes filling, the pipes in the room do a 'groaning' sound (kind of like me at this point)
Couple of questions:
-- is adding a pressure regulator difficult? and does it need to be done at the house source or could it be done in the bathroom?
-- would limiting the pressure via the Stop-Check Valves in the shower faucet make a difference? (doubting it at this point)
09-19-2005, 12:08 PM
Replace the toilet ballcock and see what happens...they're cheap, less than $10. Fluidmaster or Korky quite fill are two good brands. Replace the line from the shutoff while you are at it too. See if that makes a difference...
You are describing classic water hammer when you say it occurs when you open and close a faucet quickly. Where are the air chambers and shock arrestors located relative to those faucets? If they are not right at the faucets they will be ineffective and not stop the hammering noise.
09-20-2005, 06:49 AM
1/2" 12" riser 18" for 3/4" the manifold can be disconected and dumped.
09-20-2005, 02:36 PM
One other thing to consider after a little remodling would be to check the pipe hangers in basement or places where the pipes are anchored.
Have someone to open and close those new faucets while you watch and listen and try to find a loose pipe.
Water hammer can cause a pipe to rattle. If you check, I bet you'll find movement.
Just a personal comment. I lived in a home for a lot of years. I put a pressure gage in a cold water pipe near my water meter. I had 18" air chambers behind all lavs. had 75 to 80 lbs. of water pressure with no pressure regulator and no noise. Neither clothes washer or dishwasher caused a hammer. I may have drained the water down 2 or 3 times to unload the air chambers. I loved the higher pressure. Never had a copper leak. But I did look for pipe movement and then shimmed with pipe covering material.
09-20-2005, 06:02 PM
Thanks for everyone's comments and suggestions .. you've re-energized me to tackle it again this weekend and test a couple of the options raised. Will advise if successful ... regards, Stevo
09-20-2005, 07:56 PM
Let us know..............
09-21-2005, 08:21 AM
pick up a water pressure tester at the hardware store. it screws on to your hose bib, let us know the pressure.
keep on BANGING down the road till then :D thank,s plumber
10-07-2005, 08:49 PM
If anyone's referencing this thread later, thought I'd provide the fix.
It was actually 2 problems:
- Main issue was shower faucet ... turns out the pressure balancing spool inside the valve was making the loud knocking noise as it slid back and forth. I tried replacing just the spool with a new one but noise persisted. So finally I replaced the faucet entirely with a new model and it worked - complete silence!
- Water pressure was also too high (100+psi coming in from street) ... installed a pressure regulator on the main line, set to 60psi and pipes much quieter in the house.
Thanks again for suggestions that came in .. my reno is back on track!
10-08-2005, 07:08 PM
You said you had moved the pipes.I would bet that one of them is loose and jumping when you close the valve quickly.See if you can make some shims or wedges up and place them where the pipes go thru the framing.I was replacing some sheetrock in our ceiling and got to witness the banging first hand.I just wedged and anchored the pipe,presto no banging! :)