My house has a city water supply. The water pressure is at 60psi. Whenever a faucet is turned on (hot or cold) or a toiler flushed the water pressure pulsates as seen in this video and all the pipes throughout the house pulsate along with the water pressure. (see the video in the link above.)

What could be causing this?

Things I have tried:

  • Try to remove air pockets in the pipes by draining all pipes (hot and cold) starting with the highest faucet in the house, then slowly refilling the pipes. This seemed to work for 30 minutes or so, but may have just been wishful thinking.
  • Inspect pressure reducing valve. It is at between 15 and 20 years old and looks OK to me. (I have no idea what a bad one would look like.)
  • Ignore the problem. This hasn't work at all.

Edit 1:

  • The house was built in 1999
  • I have owned the house since 2006
  • The problem started about 6 months ago, approximately October, 2021
  • This is a two story house built on a slab, i.e. no basement
  • The whole house has copper pipes

60psi water pressurePRVPRV tag

  • Are there long runs of unsupported pipe? You might try to attache additional brackets. Also look for automatic valves that could be triggered by abrupt pressure change -- particularly toilet fill valves (and animal trough valves). Temporarily shut the flow to all toilets to see if that's the issue, and, if so, adjust or replace the float valve. Apr 3, 2022 at 21:54

3 Answers 3


The low frequency of the pressure oscillation, as observed in the video to be sub 10Hz, suggests that this is a tall or long water column (thus heavy) traveling through a section of pipe with a large air cushion in it.

In contrasty, the frequency for water hammer from expansion of plastic piping (PEX, Poly, due to its elasticity) is much higher, well in the audible range and can sound like a screech, hum or buzz.

Banging or rattling sounds are caused by piping that is not fastened properly, can move freely as a result of water hammer, which then bangs against nearby surfaces like paneling, studs etc... The solution is to properly fasten the pipes, and install water arrestors nearby problematic faucets and valves (washing machine, dishwasher etc...)

If all the piping is rigid (e.g. copper) it can also be caused by water oscillating in & out of an expansion vat, often found near the water heater.

A further cause could be any pressurized flexible garden hoses, sprinkler attachments etc..

Air pockets may occur in the house piping if the piping was emptied for plumbing work, but then a section of piping never refilled with water after the system was recommissioned. To avoid water cushions, refill the system while keeping faucets open.

Look throughout your house for faucets or other outlets in odd locations (outside, storage/basement, closed off bathrooms), and for sections of pipe that are no longer used, e.g. capped off, but still connected. Unfortunately these may be hidden in walls, ceilings & floors.

Often a vertical run (and upwards) can have air trapped in it, which collects in it over time from air mixed with water entering the house. If there is a faucet at the end, you can open it to let the air out, until water pours out. This phenomenon is in fact exploited in capped-off dry vertical pipe columns used as water hammer arrestors.

If it's capped you'll have to uncap it. Close it off with a valve rather than a cap, so that you can repeat this after any future work or after air recollects in the pipe section.

You'll need to shut off the water main before uncapping, of course. If the section has a shutoff valve at the beginning of the run, you can close the valve to see if it reduces the oscillating effect.

Sometimes an unintended "high loop" (upside-down "U") can keep water trapped in it if the flow-through is slow compared to the diameter of the piping: water streams through as in an underground canal but the air cushion never gets pushed through. Make sure it can flush through with maximum flow for sufficiently long time.

  • I again drained the whole house and very slowly refilled the pipes. It has been about 36 hours now and the problem has (so far) not returned.) So I'll mark this answer as the accepted answer Apr 5, 2022 at 17:35
  • @HairOfTheDog ok glad you got it resolved. Hard to diagnose via screen & keyboard, but your trial/error seems to have paid off.
    – P2000
    Apr 5, 2022 at 19:05

A bad PRV and a good PRV look exactly the same from the outside, for about 99.37% of "bad PRV" issues. The failures are mostly internal. You can get a rebuild kit of new internal parts and rebuild it.


I can now say with 100% confidence that this problem was solved by replacing the pressure reducing valve. I am 100% confident because I had the PRV replaced about two months ago and the pulsing water pressure symptom has never been seen since the day the PRV was replaced.

  • Those valves do use a spring, and the bouncing of the pressure needle is very spring-like. The valves also have a LOT of replaceable parts inside, though the labor to replace them could exceed a new valve cost, especially if paying a professional's hourly fees
    – Xen2050
    Dec 24, 2023 at 7:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.