High water pressure for a few seconds

Mccliff

I am facing a ‘water pressure build up’ issue in my new home, which was bought a year ago. The water comes rushing out about twice the normal pressure when I turn on any faucet in my home. It will last only for 2-3 seconds and then drop back to normal pressure in most cases. Sometimes, the pressure will not come down until I turn off the faucet and then turn it back on. The pressure seems to build up only when the water hasn’t been used for a while. I am quite concerned about this issue. I tried turning the screw on the top of my pressure regulator to down the pressure, but the water still comes out way too high when the faucets are first turned on. For the time being, I have decided to seek the help of a plumbing service in Markham to fix this. But I want to know whether is there anything I can do myself to fix this. Any help will be appreciated. Thanks in advance.

hot_rod

Sounds like the PRV has failed? Any idea what the incoming pressures is? Typically you want to stay within. 3:1 ratio
Delta P of incoming to regulated pressure

Could be the main line pressure is spiking

A gauge with a second lazy hand would record spikes

Zman

I agree
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Steamhead

That PRV probably has a backflow preventer. If there is no expansion tank on the water heater, the pressure will build when the heater comes on.

Lance

OK. Several things can be happening. Pressure regulator, (PRV) bad. Also lack of an expansion tank or if the water heater has an expansion tank, it may have failed or may not have been pressured properly to take care of pressure build up when the water heater heats up colder water.
Could be both.
Two ways pressure should be checked, one we call static with nothing running and one with flow. Pressure drop reading could be a clue to restriction or PRV problem. I recommend a water pressure gauge with a maximum pressure pointer be used to see if you are getting overnight overpressure from the main, or internal. Test two ways, 1 by isolating the main from the water heater and with the house isolated with the water main valve off. Many water meters installed today have one way valves and will not let house pressure back into the main. Pressures can exceed over 300 pounds and burst or bulge a water heater. Water gauge can be bought at depot or plumbing supply store with a hose connector and max point needle. 0- 100, may need 0-200PSI.
Water will not compress when heated so pressure rapidly increases when heated in a sealed system without room for expansion. good luck.

Jamie Hall

If you have a PRV you must have an expansion tank. That's not an option. And it must be a fairly good sized one, although it is very difficult to specify and exact size.

hot_rod

Jamie, do you mean a BFD, backflow device, instead of PRV pressure reducing valve?

Paul48

Most PRV's create a closed system, and necessitate an expansion tank.

Jamie Hall

hot rod said:

Jamie, do you mean a BFD, backflow device, instead of PRV pressure reducing valve?

Could be either one. They both act as check valves, among other things.

hot_rod

Best I recall DHW thermal expansion tanks never existed in our industry until BFD were added to water meters or as additions to PRVs

Unless the PRV has a specific listed check device?

Isn't that why boiler fill valves require listed BFDs? A fill valve is basically a PRV. We use the exact same valve with different spring settings for both application

Paul48

My thinking is that separate, additional BFD's are required because you are definitely connected to a source that could contaminate public drinking water. The same holds true for sprinkler systems. I think that by the very nature of their design, PRV's act as a check valve, unless there is a bypass included in their design. I have heard that some have that feature.

hot_rod

Paul48 said:

My thinking is that separate, additional BFD's are required because you are definitely connected to a source that could contaminate public drinking water. The same holds true for sprinkler systems. I think that by the very nature of their design, PRV's act as a check valve, unless there is a bypass included in their design. I have heard that some have that feature.

Then why BFD on domestic water supplies that don't have boilers, sprinklers, or irrigation?

I think AHJs and domestic water suppliers have learned that PRVs are not always adequate protection against reverse flow. And of course some homes and buildings don't have PRVs, or functioning ones. Common domestic water PRVs are not listed or testable for back flow conditions.

Adding BFDs at the city supply, often in the meter yoke could subject the PRV up to 150psi, assuming the water heater has an operating relief valve, and no DHW expansion device has been installed.

If you lose incoming pressure to the PRV, that is a lot of pressure to expect a PRV to work against in the wrong direction, in the event of a thermal expansion caused pressure increase, for example.

Typical domestic water PRV, are not designed to provide protection against reverse flow, certainly not a 150 ∆P condition. If they were they would have a listing certification to assure they were designed and tested to that potential condition.

Our 573 AutoFill boiler fill valves do have a small spring check on the outlet, as there was a time when that single spring check was considered adequate BFD protection.

There are many types of BFD manufactured and specified according to the hazard. Some are testable, other not. There seems to be a lot of cities now requiring listed, testable BFDs and yearly re-certifications.

Paul48

Do you see a lot of BFD's on residential supply lines? I've never seen one in this area.

MilanD

In my area, prv on the house line lasts about 5 years. Also pressure reduction should be about 1/2 of city. Anything more and prv doesn't seem to like it (psi creep). Also a functional expansion tank is a must. We are at 180psi street side. My dhw pressure safety valve told me something was off and the pressure gauge confirmed. Replaced prv. Checked and inflated expansion tank to op psi and problem solved.

hot_rod

> @Paul48 said:
> Do you see a lot of BFD's on residential supply lines? I've never seen one in this area.

If a water company receives any govt funding, it is required to have BFD

Often they are installed in the meter pit and homeowners may not know they have one

I see some third party companies now implement and maintain BFD programs for smaller cities and villages

hot_rod

> @MilanD said:
> In my area, prv on the house line lasts about 5 years. Also pressure reduction should be about 1/2 of city. Anything more and prv doesn't seem to like it (psi creep). Also a functional expansion tank is a must. We are at 180psi street side. My dhw pressure safety valve told me something was off and the pressure gauge confirmed. Replaced prv. Checked and inflated expansion tank to op psi and problem solved.
Or a like to work within a 3:1 delta p. So with high inlet like that consider tow PRVs to drop to 45 psi. First and second stage setup

Paul48

"If a water company receives any govt funding, it is required to have BFD"

I like having to pay for small towns and cities. Like the 80% of the towns in CT that we pay state police to cover, because they have no police dept.

j a_2

Are you sure you don't have a flow problem as opposed to a pressure problem. Get yourself a cheap gage at the cheap o depot and attach it to your outside hose connection turn it on observe the pressure then go inside and turn on a tub then check the pressure again. 30 psi is really the min. 80 is about the max

Jamie Hall

It would also be worthwhile, if you get a gauge, to observe the pressure after all the water has been turned off in the house. If it ramps up slowly -- which wouldn't surprise me -- the PRV is leaking slightly when it should be closed. This wouldn't surprise me, as on that much pressure drop it will be really under stress under low flow conditions, and may have wire drawn the seat. If that is the case, you need a new PRV.

j a_2

It's a nice feature to install a bypass

EvanRojas

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.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.