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I shut off the main water supply in the evening to replace the shower cartridge. I came back the next afternoon to finish the job. When I turned on the water main I started getting continuous water hammer. I shut things back down again.

I went and opened 2 of 3 sinks, the tub, and the outside hose all the way, but I still get this symptom.

I have valves to control the supply side (before the water meter) and after. The supply side is fully open, and I've been opening and closing the side after the meter.

What should I be doing so I don't ruin my plumbing just trying to fix a dripping tub spout?

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2 Answers 2

It is natural to have some water hammering when you had your water turned off for a day and turn it back on.

You probably had a sink on or something so that when you turned off the water the excess pressure pushed it out somewhere - not your shower. So your waterlines are filled up with air. The air has to go out places and will create huge air pockets that will make noise when moved. Turn on your water supply and turn on everything for a few minutes and it should quickly go away.

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Just wanted to give an update to help others. With the encouragement here, I went back and eventually got the water on. I did turn on all my faucets and outside hose about 1/3. I turned on the main until it started to hammer. I kept it there, thinking that the hammering would resolve itself. I waited at least 15 minutes, but it never went away, sometimes less, sometimes more. Eventually I turned it up, and kept turning it up, until the hammering disappeared and I could continue opening the valve all the way. So I guess with the valve open just a little, there was a region of hammering. –  jfklein May 28 '13 at 19:43
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If you turn it on just a bit and have lines open then your pipes will never fill up. You would be displacing the air through out - ie the hammering effect. You really just need to fill up the main line and push the air out the faucets. –  DMoore May 28 '13 at 20:50

I don't think water hammer is the right term for the noise you heard. Water Hammer is the slamming of pipes when a valve is closed caused by a total lack of air in the pipes. See http://www.dummies.com/how-to/content/how-to-quiet-noisy-water-pipes.html or http://en.wikipedia.org/wiki/Water_hammer

So a little air in a pipe is a good thing. Too much air can cause noise when the water is flowing. Too little causes noise right when you shut the flow off.

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