Lately when I turn on any faucet in my house the water comes rushing out at about twice the normal pressure for about half a second and then drops to normal pressure. I am worried the pressure is building up to high in the pipes. If I turn off the faucet and then turn it back on within a minute the pressure comes out normal. Its only when the water hasn't been used for a while that the pressure seems to have built up in the pipes. I tried turning the pressure down on my pressure regulator by turning the adjustment screw on top one full turn counter clockwise but the water still comes out way too high when the faucets or the clothes washer or shower is first turned on. After a second the pressure drops way down now that I adjusted the regulator.


The problem is your expansion tank, or lack thereof. Your home has a check valve somewhere in the system, possibly included with the pressure regulator or as part of the municipal water meter. When your water heater turns on, the heating of the water causes it to expand, and that pressure has nowhere to release until you open a faucet. What you need is an expansion tank installed in your water lines. If you already have one, then it has failed (they usually have a bladder separating the air from the water, and this can fail over time or if not properly maintained). Installing a tank isn't too difficult, but will require shutting off the water to your house, cutting your pipes, and adding a T to your water line. If you have an existing tank, then they are often threaded and are simple to replace (the connection is often threaded and can be screwed off). Note that if you don't fix this, valves in your toilet and other fixtures will start to fail, or the TPR valve on your hot water heater will begin to leak water.

example expansion tank

  • I don't have an expansion tank. So why would I have this problem after 40 years? My neighbor doesn't have this problem. He said my pressure regulator might be starting to go bad but its only a cone shaped brass object with an adjustment screw on top. Can these go bad? Or could my water heater be starting to go bad? However the high pressure problem occurs when I turn on cold water from a faucet too. I noticed the problem about a month ago shortly after I put a new toilet valve in one of my toilets and also about the same time I had new sprinkler valves installed. All of them say anti-siphon. – Ken Nov 18 '12 at 23:22
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    Anti-siphon is another word for a check valve, it keeps water from going from your house back into the municipal water supply (and possibly introducing contaminates). Your toilet valve probably went because of this problem, they tend to be the first to leak and keep your pressure from getting to high. Your hot and cold water lines are connected via the water heater, their pressure should be identical. – BMitch Nov 19 '12 at 1:37
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    @Ken: It's possible your old toilet valve was leaking under the pressure and so you never got the build-up of pressure you're seeing now. In fact, it's entirely possible that the high pressure caused that valve failure. – Hank Aug 8 '13 at 17:29
  • Details about expansion tanks, and installing one: diy.blogoverflow.com/2013/02/… – Jon Onstott Oct 13 '15 at 17:42

You don't need an expansion tank -- your pressure regulator (or pressure reducing valve) needs to be replaced. Water pressure on the city side is typically higher than what the consumers (toilet, shower, sinks, etc.) in your house are designed to handle (typically 50-60 psi). When the pressure regulator starts failing it will bleed pressure from the city side into your house lines causing higher than normal water pressure due to a failing diaphragm inside the regulator. Buy a new pressure regulator, install it (super easy) and your problem will be solved. Areas with high city pressure (it's around 90 psi where I live!) typically need a new regulator every 15-20 years. If yours lasted 40, you're very fortunate!

  • If that were the case, then turning off the water and then back on a few minutes later would result in high pressure a short time later. The irregularity and delay points to expanding water from the water heater running in a system that now has a check valve installed. – BMitch Aug 8 '13 at 17:29
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    Not necessarily. If the system has some elasticity (e.g. anti-water-hammer devices) then a slow leak in the regulator could slowly build up pressure in the system, which is then released the next time the faucet is run. Until the pressure had built back up again due to the leak (which could take some time) the pressure would be normal. – Daniel Griscom Jan 10 '16 at 17:50

user14440 is exactly right. Replace the regulator. I had the same situation. I never had an expansion tank for 25 Years and never had this problem. I messed with my regulator to improve my sprinkler system last summer and shortly after, I started having build up and failed toilet valves. Adjust your pressure valve lower. If the problem persists, replace it.

I used the regulator on the main line and turned it down 10 pounds, from 70 to 60 pounds and my problems stopped immediately. No more faulty toilet valves or bursts of pressure from faucets first thing in the morning. You can get a pressure gauge at any hardware store. It screws on to any hose bib or washing machine supply valve.


I have this same problem. It only started after I changed my shower valve... I suspect the valve is bleeding the hot into the cold and creating the problem.

  • Not sure how crossover would cause an increase in pressure, hot and cold water lines are connected through the hot water tank unless you have a check valve there. If you replaced the shower valve because it was leaking, then it was likely leaking because of the over pressure problem. If another valve doesn't start to leak, then it results in high pressure. – BMitch Jan 10 '16 at 14:44

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