Water hammer

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Apr 13, 2013
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I've had water hammer at my house ever since moving in a few years back. I hear it when using my master bath toilet & tub upstairs and the washing machine directly below on the main floor. I don't hear it when using the kitchen faucet or any other bathroom in the house.

What can I do about this? The loud banging is unsettling.
 
Search for "Water Hammer Arrestor"

You can self install or hire a plumber. The banging is usually caused by fast closing valves in washing machines and dishwashers. Install the arrestor as close to the culprit as possible.
 
For the toilet, most have a shut off valve near the floor that you can partially close to reduce the rate of flow, and with a lower flow rate when the fill valve shuts off there should not be any water hammer. Of course the toilet will take longer to fill, but it probably will prevent the toilet water hammer.

I'm not a plumber, but from what I think, If you can, add a dead ended upward piece of pipe near each valve that shuts off, that trapped air allows the water to flow into it when the valve closes, that may help absorb the jolt of water when a valve closes.
 
install a pressure tank. if youre on a well, check you current tank for proper pressure.
 
They are that short-lived?!!


As they’ve gone bad, I’ve replaced my toilet feed valves with the arrest or type that shuts off more slowly.

I do have a bit of a hammer due to my one long run that goes across my home. Sometimes it happens, sometimes it is not present.
The Kenmore washer I replaced about a year ago had the most severe hammer from those valves shutting off. When it finally died I replaced it with a Whirlpool and so far the new arrestors I installed after buying it have been holding up, so we’ll see.

Over time I would begin to hear the hammering increase in volume slightly. I would replace them soon after.
 
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Those arresters haven't done jack for us. I installed them all over the house and they never worked.

The only thing that works for me is draining the entire water system. This keeps it at bay for about a month and then I need to drain again.
 
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It sounds like the problem is on one line that serves that part of the house. A couple of questions; do you know the diameter of the line from the washer to the upstairs bathroom? Also, how old is this house?

If the plumbers used a ½ inch line running between the laundry up to the bathroom that would be insufficient. They do that to cut costs. They also cut costs by not installing the extra capped pipe above the connections. Better installations use ¾ inch pipe until last run to the usage point then ½ inch from there.
 
Post a rough schematic of the trunk line ( with diameter and length- all on the high side)

Pretty sure this can be remedied without much pain
 
Interesting thread........

I had never heard of the “arrestor” until very recently.

I want to use automatic timers on my outside hose faucets. In researching the various models available, the glaring comment that came through loud and clear via the reviews was to use an arrestor at each faucet to prevent damage to the pipes and plumbing joints.

I have read that you can install an arrestor for the “whole house” at the closest point to where your water main enters the house, but I’ve yet to hear how effective that would be.
 
I have read that you can install an arrestor for the “whole house” at the closest point to where your water main enters the house, but I’ve yet to hear how effective that would be.

I installed a super jumbo one at that point and didn't have a positive effect whatsoever.

I guarantee the water hammer I have would win an Olympic Gold Medal.
 
Obtain a gauge, connect it to the closest faucet towards the meter. If the pressure is over 60 psi, I would install a pressure reducer to get the pressure to 50-60 psi. Mine was running 80-85, once I got the pressure down, the hammering stopped.
 
Turn off the main water supply and drain the complete system by opening ALL faucets and let then drip dry. I had a home where I had to do this about every 6 months months to stop a water hammer. Water hammers can be very destructive.
 
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I have read that you can install an arrestor for the “whole house” at the closest point to where your water main enters the house, but I’ve yet to hear how effective that would be.
That would not work very well. Water hammer occurs when the point of use closes suddenly so the water moving in the pipe must stop quickly. An arrestor at the far end will absorb this impulse of pressure instead of it hammering to a stop. One at the supply end might only help on a second wave of repeated hammering if a wave starts moving back and forth.
Turn off the main water supply and drain the complete system by opening ALL faucets and let then drip dry. I had a home where I had to do this about every 6 months
If you have the tradidtional setup of a vertical dead-end pipe to hold a bubble of air, eventually the air will be absorbed in the water and it will no longer be effective until you drain the pipes to establish a new bubble. Of course any unintentional bubble would do the same thing.
 
Hydraulic Hammer is not difficult to remedy ( assuming a properly built system) but in order to do so, the solution(s) have to be rated superior to the effect of the hammer on it or it will be overwhelmed and fix nothing.

In addition, the placement in relation to the wave ( positive or negative phase) has to be correct too otherwise the wave velocity will overwhelm it too

Need to differentiate true hydraulic hammer versus air slugging- both can rattle pipes
 
If you install an upward dead end pipe, you should have a smooth transaction of the direction of flow of the long run of pipe as it gets to the upward dead ended pipe that holds air.

In other words, if the long run is horizontal, like below a floor, you want a section of pipe with a decent radius between the end of the long run and the entrance of the upward dead end. The water should be making smooth turns to enter the upward dead end if it has to make any turns. A sharp 90 may prevent the water from being able to access the dead end air space smooth enough, and you would still get a water hammer even if the upward dead end pipe was long enough to contain enough air to do the job of absorbing the jolt.
 
When I bought my house it didn't have a washer, but it had the hookups. The washer I bought water hammered so bad it broke every lime deposit in the pipes free and plugged every water outlet except the kitchen sink!

I did arresters and no issues. However, I recently moved the laundry room and did not put in the arrestors and I don't have water hammer issues. I used Pex FWIW.
 
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