Vibrating cold water pipe...

[pug_ster]

Hello,

I own an 80 year old 6 family, 3 story building. Sometimes I would hear the water pipe vibrating. We noticed that the water pipe vibrating right after when the cold water got shut off (IE turning water off a sink). It would vibrate for about 3-4 seconds and it would stop vibrating. When the cold water vibrating, it would go from the walls upstairs in the apartment to the basement next to the water meter. I had contractors who would come in from time to time but doesn't know what what caused the pipe to vibrate. Thanks.

[pug_ster]

Actually I believe the problem is caused by water hammer.

I shut off the cold water main, turned on a faucet in the basement. After all the water is drained, I turned on the water again. Now the thumping has stopped But I think I will need to get someone to install the water hammer arrestor. Thanks anyways.

[HayZee518]

think of your water line as a long vertical run with branches at each apartment. if the lines aren't supported to the studs along the run, they will move, even when they branch out from the main run. even cold water lines expand and contract. to arrest the vibration a two foot "stub up" at the line's highest point may cure the problem. the vibration could be visualized as the cold water being shut off at a faucet, being throttled down that the faucet washer doesn't securely meet the faucet seat, so it vibrates much like a reed in an instrument. with an air column in an arrester this sudden shut down of the water flow will compress the trapped air in the stub up and act as a shock absorber.

[pug_ster]

Thanks for replying. What do you mean that I put a 2 foot stub up? Do I put an arrestor coming out of the 3rd floor (highest floor) bathroom and/or kitchen cold water line? Do I have to put arrestor(s) along the main water line in the basement?

[pug_ster]

I thought about getting a professional plumber that might be able to help me to fix the problem but I went into the cheap route. I brought 2 sets of 1/2" Water Hammer Arrester, 3/8" x 3/8" x 3/8" compression T valve and a 3/8" to 1/2" supply line tube. I installed this in my toilet and bathroom cold water sink line 2 days ago. I do hear some vibration but it is significantly reduced.

The reason why I brought this is that Home depot only have Water Hammer Arrester in 1/2" size. I assume that people use this for a washer machine or a garden hose. I'm going to a plumbing supply store and maybe they would sell water hammers for a bathroom toilet or something.