Water Hammer - How Many Arresters Needed?

[Sterling]

I have a water hammer issue mainly affecting two bathrooms, one directly above the other. The hammer is present when both toilet valves close, when closing the cold water on both sinks and when closing one of the shower valves. I added arresters to the washing machine about 10 years ago and it seems fine. When the house is quiet I can hear the shock wave moving back and forth until it dissipates. I originally thought I had unsecured copper pipes but have ruled that out. The normal water pressure is 58 PSI. I can easily access the 3/4 copper right before it splits to the two bathrooms. Would adding a single arrester at that point accomplish anything? Or will I have to add arresters at every fixture?

 

[Reach4]

Are you closing the cold water valves on the sinks and the shower controls rapidly? That is not what is normally done, so those don't usually need water hammer arresters. Water hammer is a single bang when you close a valve quickly. Is that what you hear-- a single bang?

And do you hear noise when you close those valves fairly slowly/softly?

 

[Sponsor]

 

[Sterling]

Thanks for the reply. The valves aren't being closed unusually quickly. Just normal use. If they are deliberately closed slowly there is no noise. And yes, when the valve closes it bangs hard (so much that I thought a pipe was loose). The one hammering shower valve definitely has a shorter "throw" to turn off than the one that doesn't hammer. Both sinks have modern single handle fixtures that open and close by moving the lever up and down. I suspect I wouldn't have an issue with old-school taps that required twisting to open and close.

I did try draining the whole system and that did stop the hammer for about 2 or 3 uses. I am pretty confident that water hammer from fast closing valves is what I am dealing with.

 

[Jeff H Young]

normaly you dont need any water hammer arrestors. if you dont have low flow water saver restrictors or if you tampered with or removed them , you are much more prone to have hammer. So the water hammer has always been a problem?
Im all for adding the arrestors when it works just saying there is a cause loose pipes is a common cause

 

[Sterling]

The water hammer seems to have become an issue over the last few years as the plumbing fixtures have been replaced. Nothing has been tampered with. And being recently retired, I am just home more now to hear it. For example, if I stand in the adjacent room while someone closes the shower valve, the bang is much more obvious than to the person using the shower. I have stuck my head up into the basement ceilings and have found no sign of any physically loose pipes. The house is relatively small and the copper lines are relatively simple. As I mentioned, I added arresters to the washing machine about 10 years ago. It was the only problem back then and the arresters worked on it.

 

[Jeff H Young]

Sterling well adding the arrestor might help Ive found on severe water hammer issues I sometimes get a little sound from the arrestors. its almost a science on all the things that can cause it Ive found partialy pinched off copper lines or blocked with pebbles can cause it not to suggest these but just an example. If flow starts out fast and then slows down after a number of seconds its a sign that contributes to hammer. sounds like your problem is anoying but not horrible . so another arrestor and or something Ive never tried and not suggesting but might actually help might be an expansion tank. if you have a water pressure regulator Id probebly put one . but just adding one would be an expirament .