Static water pressure changes

[Jona77]

Hi,

I just had my ancient strainer and pressure regulator replaced and they added a gauge on the house side of the regulator.


The plumber initially had it set at 65PSI. I turned it down to 60 static, with the shower running it sits at about 55. I noticed however that after a period of time of no water usage the pressure rises to around 75. L

Is this normal?

Is it just the water in the house warming up and expanding?

Is there cause for concern or a potentially faulty new regulator?

thanks

 

[Reach4]

Is it just the water in the house warming up and expanding?

Is there cause for concern or a potentially faulty new regulator?

Could be either.

If you turn off the WH heat for testing, you know there is not significant expansion. There will still be a bit of expansion as the house heat heats the pipes.

 

[Sponsor]

 

[Jona77]

Update:

the regulator works normally when water is running. With all fixtures shut off it climbs and stops at 88PSI

I texted the plumber he said it should be fine.. so static is 88 and running is whatever I set it to.. should a PRV hold the set pressure in static situations or will city main pressure leak through in static situation?

update 2: it’s now sitting at static 50 and not rising (pressure regulator 8: current set at about 45 with flow. same was it was when I saw the 88)

I’m wondering if there’s air in the gauge line

 

[Themp]

You did not state if you have an expansion tank along with the PRV? And it can get more complicated in that your PRV may allow dynamic bypass back to the city. And some city meters now have check valves which then makes them a closed system requiring an expansion tank. If you have a closed system then an expansion tank will help keep the pressure at the PRV set point. Do an internet search on PRV and expansion tank and you will get a bunch of links. Add Terry Love to the search and you will get a nice list of links to this forum with this discussion over the years.

 

[Jeff H Young]

When a pressure regulator is bad it can hold water running at where ever you set it but if you turn fixtures off pressure creeps up thats not what it supposed to do. read up on it a bit its simple but 38 psi if your water heater isnt coming on tells me its your regulater

 

[Jona77]

No expansion tank, the static was about 75 when I just first checked it then I just checked with the running cold water the pressure dropped to about 50 during running and is staying there now that it’s shut off.

yesterday when it climbed to 88 max my wife had just showered.. so I think what you guys are saying about thermal expansion may be the reason.. I’ll run some more tests and update later today

is an expansion tank the answer? 88 seems dangerously high.. that being said it was probably doing the same for the last 50 years and hasn’t been a problem?

 

[Reach4]

No expansion tank, the static was about 75 when I just first checked it then I just checked with the running cold water the pressure dropped to about 50 during running and is staying there now that it’s shut off.

yesterday when it climbed to 88 max my wife had just showered.. so I think what you guys are saying about thermal expansion may be the reason.. I’ll run some more tests and update later today. Note that some pressure gauges have a second "lazy" hand that records the peak pressure. Those lazy hands can move due to vibration. The drain on the WH is one place you can attach such a gauge for testing.

is an expansion tank the answer? 88 seems dangerously high.. that being said it was probably doing the same for the last 50 years and hasn’t been a problem?

1oo is not dangerously high for normal pipe. 120 is not dangerously high for normal pipe. 150 is not dangerously high for normal pipe, but some devices like toilet fill valves may have a problem. Pipes should not have a problem.

What would it take to repipe to PEX?

 

[Jeff H Young]

88psi I dont think is dangerously high but I belive higher than desired.
Id say determine if youve got a closed system if so yes add tank

 

[LLigetfa]

80 PSI is the code max in many jurisdictions after which a regular is required. Static pressure can vary on municipal systems for several reasons. If the municipality relies on water towers for pressure, the level of water in the tower affects the static pressure. When the municipality is pumping water into the towers, it can raise the static pressure.

The term "static" implies the pressure when there is no water drawn. When water is drawn, there is friction loss that can/will affect the pressure. Water draw can include what neighbors draw.

In some installations, the pressure regulator might be downstream of where outside hose bibs tie in in which case a pressure gauge can be attached to the hose bib to measure the pressure before the regulator.

 

[Reach4]

80 PSI is the code max in many jurisdictions after which a regular is required. Static pressure can vary on municipal systems for several reasons. If the municipality relies on water towers for pressure, the level of water in the tower affects the static pressure. When the municipality is pumping water into the towers, it can raise the static pressure.

What are you saying? Surely you are not saying that a thermal expansion tank should keep the pressure from rising over 80. Yet if you are not saying that, then your post seems unrelated.

 

[LLigetfa]

What are you saying?

What I was NOT saying is anything about expansion. The OP seems concerned about the 88 PSI and I simply stated that code addresses anything above 80 PSI static (infer excessive) but not factoring expansion. Extremely excessive pressure IMHO is the pressure that is relieved by the TPR on the water heater but any pressure above 80 PSI should be considered excessive. Unless the home has dodgy piping, I would use 60 PSI as the target "regulated" pressure and between 60 and 80 as the expansion max pressure.

This thread title is about static pressure but static pressure upstream of the regulator is not being measured so unclear whether the measured pressure is from a faulty regulator or expansion.

 

[Reach4]

What I was NOT saying is anything about expansion.

Unless the home has dodgy piping, I would use 60 PSI as the target "regulated" pressure and between 60 and 80 as the expansion max pressure.

Mixed message. You seem to infer that in a normal well designed system that the water pressure should never rise to even 90 psi due to thermal expansion. You are not the first.

See what you can infer from this: http://tools.watts.com/ETP/

 

[Jeff H Young]

in original question op was asking about whether its normal to get a 20 psi differance in pressure . I would say if water heater is off it shouldnt creep like that with new regulater installed but maybe it will seat better in a few days weeks. He never did mention incoming max pressure that matters too it might not be any higher than 88 psi

 

[Jona77]

So the plumber is coming back on Monday to install a expansion tank for the hot water heater

it’s thermal expansion for sure I’d say. only happens when hot water is used the prv has a check valve in it he said so it is a closed system after the prv