Water hammer arrestors?

[Frederick Skelly]

Hi folks.
I'm looking for information and experiences with water hammer arrestors. I have a year old dishwasher that "bangs" the pipes for the first few minutes after it starts running. In the back of my head, I keep thinking that banging might ultimately loosen a joint and cause a leak somewhere in the house. In addition, Ive noticed my washer does the same banging too, but to a lesser degree. I recently realized there are such things as water hammer arrestors.

1. Do they work?
2. Do they make a "whole house" arrestor - maybe something I could install in the basement? I've only seen the kind you place near the appliance.

I'd appreciate any experience or advice you can share, please.

Thank you,
Fred

[Ron Selzer]

take it for what it is worth as I have not dealt with water hammer before but have dealt with water expanding when heated sure seems like a small air bladder expansion tank piped somewhere in your system would handle this problem for you.
I have always lived in a house that has a pressure tank or expansion tank installed
Good luck

[Jerry Bruette]

Yes they work. I have them installed on the wash machine. The plumber installed some permanent ones when the house was built but they would get water logged. Then they wouldn't work and we'd have to shut off the water pump and drain the pipes to allow air back into the chambers. Got tired of that game and installed some spring loaded ones that attach between the hose and the washer.

Never heard of a whole house arrestor. My understanding is they have to be used at the end of the line by the appliance.

[Stan Calow]

Yes they work. I have them on my washer, hot and cold as per photo:
washer.jpg

Water hammer occurs when there is a sudden open and close of a valve like in your washer, or toilet. The water, which is rushing to the open valve suddenly stops when the valve closes and the pressure increase form a sudden stop causes the banging as the water can't compress. My washer, in its cycle, will open and close the water valve several times as it rinses out the detergent/bleach/softener and senses the load in the washer. So it used to bang like heck several times in a row, enough to get the washer to move. I installed the hammer arrestors (Sioux Chief is brand I prefer) easily myself (dont forget the tape). But I have had to replace them every few years. They need to be installed close to the valve where the hammer occurs, so they are made to go between the washer hose and connection on back of machine. Got them at the local hardware store so it must be a common problem.

[Lee Schierer]

As stated above water hammer is caused by valves closing quickly on a pipe that has high velocity flow. Solenoid valves are the usual culprits. Several things to look at. What is the pressure in your water system. Lowering the pressure (which also reduces flow velocity) may be all you need to do. A water pressure regulator can solve the whole house problem. Water hammer arrestor with captive air bladders or spring pistons mounted close to the shut off valve can cure individual problem pipes.

[Ed Aumiller]

Very often you can simply put a pressure tank WITH a bladder in it to help if you have city water supply...

If you have a well or cistern system, you may need to ADD air to your existing pressure tank, especially if your pump starts every time you turn a faucet on...

[Kev Williams]

Our houseboat has a small expansion tank mounted just above the fresh water pump,
it's mounted to the other side of that plywood board-
expansion tank.jpg
It's the ultimate in simplicity, it's just a quart-size fairly thick plastic 'tank' that's totally empty-
you just mount it empty with a Tee, the pipe fitting on the bottom as shown, then turn the water supply on-

If it's sealed properly it can't fill with water, and the air inside absorbs any water shock. It works great
on the boat, RV pumps hammer pretty good when they're close to shutting down at full pressure,
this tank absorbs it all nicely.

It's the only one I have experience with. Amazon has many versions of these, mostly in copper/brass. Not expensive...

[Bill Dufour]

In a laundry room it is simple to make one from a length of capped pipe. Tee with a valve on the bottom. When it gets waterlogged shut the valve off and open the drain faucet upstream of the shutoff. That faucet is set up to drain into the laundry tray. You need one arrestor for hot and one for cold. I suppose they could be tied into one chamber
Bill D

[Tom Stenzel]

In a laundry room it is simple to make one from a length of capped pipe. Tee with a valve on the bottom. When it gets waterlogged shut the valve off and open the drain faucet upstream of the shutoff. That faucet is set up to drain into the laundry tray. You need one arrestor for hot and one for cold. I suppose they could be tied into one chamber
Bill D

^--- This is what I've always done for my plumbing, a vertical capped pipe just before the valve. Haven't had problems with the air leaking or finding it's way out.

-Tom

[Stephen Tashiro]

2. Do they make a "whole house" arrestor - maybe something I could install in the basement?

Do you have a pressure regulator installed somewhere? City water pressure is usually higher than the recommended pressure for household plumbing.

[Frederick Skelly]

Thanks for all the help guys! Sounds like it's worth trying, whether I build or buy one.

Do the store-bought variety have any tendency to leak? The supply valve to my dishwasher is only about 3 inches from the electrical outlet for the garbage disposal. So the hose connection to the arrestor will be very close to the outlet, which makes me a tad uncomfortable.

Thanks very much!
Fred

[Jerry Bruette]

Thanks for all the help guys! Sounds like it's worth trying, whether I build or buy one.

Do the store-bought variety have any tendency to leak? The supply valve to my dishwasher is only about 3 inches from the electrical outlet for the garbage disposal. So the hose connection to the arrestor will be very close to the outlet, which makes me a tad uncomfortable.

Thanks very much!
Fred

Mine have never leaked. Just be sure to get them tight.

[ChrisA Edwards]

Timely thread, I just replaced a leaky cold water fill valve on my 6 year old LG washing machine.

This machine was the first one, we've owned , where the banging occurred each time it filled.

After the new cold water fill valve was installed, no more banging on fills. I can only assume they altered the rate the valve closes to eliminate this.

Before this thread, I was not aware of these Water hammer add ons, I think I'll add a couple of these for good measure.

[George Yetka]

Sure. I would add a small one under the sink at the anglestop that feeds the dishwasher if needed. this one makes it very easy. take off the hose install this put the hose on the other side. 2 small adjustables is all you need

https://www.amazon.com/sicoince-Arre...xpY2s9dHJ1ZQ==

[Malcolm McLeod]

..I'd appreciate any experience or advice you can share, please.

Thank you,
Fred

For the info geeks out there, and as several others have alluded to, the problem is caused by the momentum of moving water. That kinetic energy has to go somewhere when the valve slams closed, so it gets transferred to the pipe. The longer, larger the straight run of pipe into the valve or the higher the velocity, the worse the potential issue will be. (Try this on 35 miles of 10"D pipe! ...use really slow valve actuators.)

I've always heard this problem in conjunction with hard copper water lines, and I've always been told by plumbers that the 'proper' solution is to firmly and permanently secure the pipe during installation. It can't 'hammer' if it can't move. (I think Pex would obviate most of this?)

One caveat on the arrestors: They should have a bladder AND a way to re-charge the air-side chamber (i.e. a Schrader valve). If no bladder, the air will ultimately get entrained/dissolved in the passing water - - and be gone :: no more arresting by the arrestor. If the bladder leaks, you get the same result. Including an air valve and a means of physical access to the arrestor allows you to recover without draining most or all the system.