About every 5 minutes my pipes pulsate for about 30 sec. I have just done a renovation and added new plumming fixtures.
The city has flushed their pipes.
Do not have a sprinkler systen or surge tank. I did turn off the water to the hot water tank and the surging stopped. Both my plummer and the city don't have a solution. Please help - its driving me crazy.

How long since you drained and flushed you water heater?

The water heater is lesss then 2 years old and I have never drained or flushed it. During the remodeling the plummer connected new inlet and outlet PVC(?) pipes.

Did the plumber install any kind of device on the output line of the water heater? I know of one municipality that requires a pressure regulator on the water heater outlet pipe if CPVC pipes are used.

Nothing was installed on the output line. The only thing different is that he put a flex line on the output to connect to the CPVC.
I'm draining and flushing the water heater and will post the results.
As far as I can determine there is no pressure reducer on the main line.

Was any kind of hot water recirculating pump installed?

Thanks for the replies.
No recirulationg pump.
Finished draining and flushing the water heater. Pretty clean except for some stuff that looked like sawdust? Still has the same problem.
When I turned on the faucet closest to the heater to vent the air, it vented for about 5-8 minutes and now no water from the open faucet.

No water, hot or cold or both, single leaver or two handle faucet? Remove aerator on spout. Any water?

It's a two handle faucet but only the hot side was effected. Cleaned the aerator and feed line, both had grit in them, but still some grit in the shut off valve. Hot is still very slow but will have to shut off the main valve to clean the sink shutoff valve.
Biggest problem is that I still have the pulsating pipes although I think it is a little less after draining and flushing.

I have the impression that the pulsating occurs even when no water is being used. Am I correct or is it only when hot water is being used?

You are correct, the pulsating occurs with no water being used, about every 10 minutes for about 10 sec.

If you had no recirculating pump installed under the cabinet or near the end of the line of you renovation, you must have something not plumbing related rubbing or vibrating a pipe. Sure sounds like a recirculation pump.

Thanks for your help.
Will start where the water comes into the house and try to find any interference or plumbing issues.
If I find an answer I'll post results so others won't have to go through all this trouble.

Would this be a gas or electric heater?

It is an electric water heater

This may seem silly, but humor me. The next time the pipes start to shimmy go out to the water heater and place your hand near the hot water outlet nipple. More vibration there? Now try the cold side. The way I track down a noise problem is to track it back to where the vibration's the greatest. That's the source and once you know that you got it whipped. Cheers, Tom

When you flushed the water heater and refilled it, did you open ALL of the hot water faucets in the place when it was filling? If you didn't , there is more than likely some air still trapped in the water heater and the pulsating is from a heat expansion taking place. I always open all the hot faucets and run the water into the heater and make sure there is absolutely NO AIR coming out before closing them.

Handyman, I don't believe it's air in the lines that's causing the pipes to pulsate. If it were air simply opening any hot water faucet would bleed the system down. But I like the way you went about analyzing it. Heat expansion in a water heater expands one mof two ways. It expands back down the cold water inlet or it expands into a expansion tank. It don't run around knocking pipes. But still, good reasoning on your part.
TRIX; Herald may be on to something. Do you have a recirculation pump installed? Regards, Tom

Tom- The hot side, at the nipple does not vibrate however the cold side does. This may not be a fair comparison because the cold side has about a 1 foot long flex pipe before it connects to the CPVC

Handyman 2007 - I drained and flushed again and refilled with all the hot water faucets open. Closed the farthest away faucets first. It helped a little but still vibrating with the circuit braker still off, cold water.

Do not have a recirculation pump installed

Recap;
This occurs when no water is being used.
The only thing that seems to make it stop closing the valve on the water heater inlet.
The heater is approximately two years old and this did not occur prior to renovations.
Turning off power to heated has no effect.
There is no recirculation pumps or "instant hot water devices" installed.

Are all of the pipes CPVC or or part copper and part CPVC?

There is no recirculation pump, is there a recirculation line? May sound like a strange question but that's the set up I have, where gravity and syphoning cause the recirculation.

At this point I would suggest that the vibration is in the water it self, not the pipes because closing the cold water valve on the heater is the only thing that will cause a change.

Suggest turning off main house valve to eliminate outside world. If vibration or pulsation is there with main valve closed the source has to be in the house.

After thought, do you have fridge with ice maker, or water dipenser, could something there be causing vibration.

The renovation is CPVC and original house is copper. I isolated most of the new plumbing, CPVC, but the vibration continued.

I'll have to check on the gravity and syphoning. Need to check what was installed and see if anything could cause that problem. This may be the answer

Closed the main house valve, pulsating still exists.

Closed the frig ice maker valve. Pulsating still there.

I turned off the cold water inlet valve to the water heater to revarify the pulsating stops. It stopped.

Would an expansion tank installed on the cold water inlet side of the water heater help?

Cold water input of heater is connected by a flex pipe to CPVC. Stop valve on the CPVC right? CPVC added to existing copper from main line into house right? I'm guessing water heater was relocated.

If it is indeed the vibration in the water, or water movement within the pipe, and not the pipes themselves, as suggest by it ceasing upon closing the heater input valve, we have eliminated the outside world and source must be in the house.

Please close valves at each fixtures, one at a time, and see if you can cause a change.

Your assumptions are correct except the water heater was not moved. The water heater is on a wall ajoining the new construction so the CPVC came to the water heater.

I'll start turning off valves and post the results when I finish.
Thanks

The first toilet I isolated seemed to solve the problem. I may have others but this seems to be the fix.

Thanks to all that helped.

Tell us more. You mean to say that a loose washer in a toilet cause all this?

My plan was to close each water valve a one at a time and see if it made a difference. When I closed the first toilet shut off valve the pulsating stopped. I kept the valve closed all night and then replaced the toilet fill valve and opened the shutoff valve this morning. So far I haven't heard or seen any pulsating. Last night was the first night in about 3 weeks I haven't heard the noise.

Flushing the hot water may have helped some.

I still may have similar issues but following the suggestions above I hope I'll be able trace them down.

Kudos and congratulations on a great job of analyzing and tracking down a difficult problem. Give yourself a pat on the back and two weeks vacation.
I love it when a asker. Especially a female, can go in and do a job just as good as a licensed plumber. GOOD JOB! Tom