Water hammer

[CMV]

Way off topic - sorry - but figured you guys would know this & get me going in right direction....

Replaced washing machine a couple months ago and ever since have had a bad water hammer effect in our upstairs bathroom. Always had a tiny one, but now it's unbearable. Used to, could hear the pipes make one soft "thud" when a downstairs toilet stopped flushing but it was very seldom. And one small noise & that was it. Now, after putting new machine in, those pipes make all sorts of racket pretty much whenever it is running. Oddly, even just when it's washing - not cycling water on/off - there's still noise. Running the shower in master bathroom (downstairs) makes the one upstairs make all sorts of racket now even if washing machine isn't doing anything. Much louder now and continual banging noises when it happens vs just one soft thud occasionally when something closed a valve.

SO I bought a set of water hammer arrestors from Lowes: https://www.lowes.com/pd/Sioux-Chief-Copper-3-4-in-Hose-Pressure-Reducing-Valve/3172327 they're pretty small but just screw in between the faucets and washing machine hoses. That helped some, maybe cut it 25%. In addition to that I tried partially closing the faucet valves to the washing machine going as far as to just let them trickle and take 20+ min just to fill. Also tried partially closing the main water valve basically reducing water pressure to whole house a little bit.

But really the only thing that makes it stop is to go upstairs and run some water in the shower when it happens. Turn that shower off, and it starts right back up in a minute.

The upstairs shower is the farthest plumbing from the main water line and hot water heater. That's only place in house that has this water hammer issue. Opening a sink or flushing toilet in that bathroom doesn't seem to do anything to stop the water hammer - only the shower. It's one of those one-piece fiberglass bathtub and shower stall type things too, so seems it would be pretty difficult to get to the pipes going to the shower valve but those are the ones making all the noise.

Not sure what to do next. Hate to replace a brand new washing machine, but I suspect it is somehow the culprit as this happened immediately after putting it in. I saw some larger arrestors/pressure tubes at Lowes that get sweated into copper pipes. Maybe that's what I need and the ones I bought are too small? If so, no idea where to put it - near the noise or near the main valve? Plenty of room behind the washing machine so I could buy a few more of what I have and just put a few in series if that would do anything - they look like they would thread into each other so I could make a chain of them in that would shut these pipes up! Instructions said could be installed in any direction.....I installed with the tubes pointing straight up if that matters.

 

[ch1ch2]

Are your water lines at the washing machine tightly affixed to the wall?
Seems to me most water hammer issues have the pipes moving. Less movement less hammer.

 

[CMV]

At the washing machine, yes. I would suspect if I tore into drywall in upstairs bathroom would find those pipes not well secured.

Washing machine is on first floor in a laundry closet in kitchen. Pretty much right behind where my main water valve is - within a few feet. All the noise happens as far away from that area as you can get.

 

[ch1ch2]

Been a while since I retired and I have forgot a lot, and I forget more everyday.
As I recall.... water has mass and that mass can be very heavy. When a valve shuts fast, that mass has to stop moving fast. That causes the pipes to shake or move causing the hammer noise.

 

[oosik]

The hot/cold water pipes going into my wash machine close with an audible clunk when the machine opens/closes its valves. It's not objectionable - just noticeable. The water moving thru the pipes has its movement stopped so rapidly - the mass slams into the valve and will cause the pipes to shake slightly. Will also make the "clunk" sound.
There are water hammer solutions that can correct this condition - if it's objectionable.

 

[PILOON]

Actual devices are sold for water hammer problem,
however,
A water hammer 'silencer' is really simple to make.
It is a section of pipe in which there is trapped air which absorbs the shock wave so to speak.
Somewhere in the water line near the washer cut, insert a 'T' and add a capped short ,6 inch or so length of pipe.
Note that short length must be vertical and empty after soldering is finished.
That pocket of air will act as a shock absorber to lessen or eliminate the bangs.

They also sell commercial units to do this but as described U can fabricate one.(also need vertical installation)

I am on a well and my pressure tank being a bladder type unit takes care of water hammers.

 

[Raspy]

CMV,

It's possible that you have water hammer risers in the wall behind the washer. These fill up with water eventually and lose affect. So the first thing to try is to drain the house. Shut off the water where it enters the house, open the outside fixtures and inside sink and shower valves. Disconnect the washer hoses and open their shutoff valves to allow air to go into the system. This will get air to all of these in-the-wall arresters, if they are there. Turn any electric water heaters off and gas water heaters to pilot while doing this. Then re-fill the house and see if that helped. If not, get bigger arresters that screw on at the hoses. The little ones that are about the size of a thumb are often not big enough. You should also have an accumulator on the cold side of the water heater. These can help with hammer as well as thermal expansion. If you already have one, make sure its pressure is a little below the street pressure while you have the house drained.

To re-fill the house, turn off the outside hose bibs and just crack the inside faucets. Then turn on the main shutoff part way. Close the faucets as they begin to run with water only. Then open the main all the way. Start the water heater(s). Then see if the water hammer is gone.

 

[ch1ch2]

CMV,

It's possible that you have water hammer risers in the wall behind the washer. These fill up with water eventually and lose affect. So the first thing to try is to drain the house. Shut off the water where it enters the house, open the outside fixtures and inside sink and shower valves. Disconnect the washer hoses and open their shutoff valves to allow air to go into the system. This will get air to all of these in-the-wall arresters, if they are there. Turn any electric water heaters off and gas water heaters to pilot while doing this. Then re-fill the house and see if that helped. If not, get bigger arresters that screw on at the hoses. The little ones that are about the size of a thumb are often not big enough. You should also have an accumulator on the cold side of the water heater. These can help with hammer as well as thermal expansion. If you already have one, make sure its pressure is a little below the street pressure while you have the house drained.

To re-fill the house, turn off the outside hose bibs and just crack the inside faucets. Then turn on the main shutoff part way. Close the faucets as they begin to run with water only. Then open the main all the way. Start the water heater(s). Then see if the water hammer is gone.

Thank you Raspy, though I am not the OP, knew there was something I was forgetting. Those water line risers are part of code for most new two story construction. My old houses did not have them and my current house is one story. My memory is OK, its my recall that does not work.

 

[Raspy]

Actual devices are sold for water hammer problem,
however,
A water hammer 'silencer' is really simple to make.
It is a section of pipe in which there is trapped air which absorbs the shock wave so to speak.
Somewhere in the water line near the washer cut, insert a 'T' and add a capped short ,6 inch or so length of pipe.
Note that short length must be vertical and empty after soldering is finished.
That pocket of air will act as a shock absorber to lessen or eliminate the bangs.

They also sell commercial units to do this but as described U can fabricate one.(also need vertical installation)

I am on a well and my pressure tank being a bladder type unit takes care of water hammers.

These stand pipes only work for a while because they fill up with water and have to be re-charged with air after a while. Note my post above. They are commonly installed behind the washer valves while building and are about 12" long. The problem with the bladder tank acting as a water hammer device is that it is typically at the wrong end of the pipe and far from rapidly closing appliance valves. It's the slug of water after the pressure tank that causes the hammer as it is abruptly stopped by an appliance valve, or sink valve. Those pressure tanks will control the thermal expansion and reduce pump cycling though.

 

[jimainiac]

It sounds like you have very high water pressure. Are you on a municipal water system? Do you know what your actual water pressure is? We once lived where we were on town water, and the pressure was quite high, resulting in banging pipes. The water hammer arresters help, but I ended up adding an adjustable pressure reducing valve near where the water line came into the building. I was then able to turn the pressure down to an acceptable level.