Do I need a pressure reducing valve?

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Mj23

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Two-story house, approximately 5500 ft.². Uponor Pex pipe throughout.

House is 13 years old, although I have only owned it for two years.

Water pressure measured at outside hose bib at 70 psi, with occasional spikes up to 90 psi. I think the spikes primarily happen at night.

I have an expansion tank, but I do not have a pressure reducing valve. I believe that the system is open.

I have had a slab leak in the last six months. Plumber thinks I need to install a valve to keep from having future leaks.

would you install a pressure reducing valve? If so, what pressure would you keep it up, at in a house of this size?

do I really need a pressure reducing valve or will the expansion tank ”absorb” the occasional spikes?

is there any harm to having a pressure reducing valve?
 

Breplum

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No harm in having a PRV. In my o., the spikes are ok.
Your old Uponor pex if colored is the era that is experiencing massive failures due to the color application concept Uponor used back then.
Contact Uponor should you need to replace every and anything. Sadly, ticking time bomb.
 

Mj23

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No harm in having a PRV. In my o., the spikes are ok.
Your old Uponor pex if colored is the era that is experiencing massive failures due to the color application concept Uponor used back then.
Contact Uponor should you need to replace every and anything. Sadly, ticking time bomb.

I have the clear Uponor pex pipes.

from reading other posts, it seems that even with having an expansion tank like I do, these occasional spikes can happen, and are OK, unless they get over 120 psi. I have never had one quite that high.


How important is it to have a pressure regulating valve? Are these occasional spikes to 90 or 95 psi enough of a reason to install one? Usually pressure is around 70 to 75 psi.
 

Jeff H Young

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Id say you are right where the divider is between having a prv and not having one make sence. I see about 3/4 of my jobs have prv,s over 80 its not debatable technicaly you should have one but Its up to you I dont think its going to cause a leak nor do i think its going to imediatly make a differance long term I think its smarter to install a prv but they arent free and dont last forevever my opinion is install a prv
 

Mj23

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I want to make sure that my expansion tank is installed correctly.

I have 2 50 gallon water heaters.

how big of an expansion tank do I need? What air pre-charge should it be Set at?
 

Reach4

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https://www.watts.com/resources/planning/etp is a sizing calculator that is more complex than many.
Even if you don't want to fill in the blanks, it will show factors that factor in. While I would put 130 into the "Final Pressure" box, some may be more cautious. I would comment that if somebody would put 80 into that box, they might be shocked at the size tank needed to stay within that limit.

https://s3.amazonaws.com/s3.supplyhouse.com/manuals/1260456129163/20367_PROD_FILE.pdf is another set of info.
 

Mj23

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Thank you. I have monitor the pressure for a 48 hour period.

incoming pressure is 75 psi. There are occasional spikes to 90 psi, but I don’t know when the spikes occur. I don’t think they are related to complete the thermal expansion and may be related to fluctuation at the main .

I agree, it is borderline for having a pressure reducing valve installed, and I am getting quotes around $1200 , labor included.

I am leaning towards getting one, but it doesn’t sound like an urgency from reading all of the replies.
 

Reach4

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I would lean away, myself. What you see as 90 psi spikes might just still be thermal expansion that you would still see after a PRV was installed.
 

Jeff H Young

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Being a plumber I didnt concider the cost 1200 bucks for what size regulator ? Just wondering and where you would mave to mount it is it galvinized pipe? Honestly on my own house Id probebly concider further investigation and no rush to buy anything . no sence having an x tank on an open system. Im not understanding how you know it gets to 90 psi it could be a slight water hammer that bumps that tattle tale needle on the pressure guage when a toilket or valve shuts off
 

Mj23

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you are absolutely right. It could certainly be a waterhammer that bumps the red needle on the pressure gauge. I have never seen the black needle go above 75 psi.

If it is indeed just a water hammer, do I need to worry about that? Will a pressure reducing valve even change that?
 

Jeff H Young

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I dont think a regulator would change the hammer except that you would likely set it lower than 75 psi and lower pressure generally means less hammer , that little bump shouldnt hurt .
 

Reach4

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Mj23: Watch your needle, or make a movie of your needle, after taking a hot shower and all water use is then stopped. No toilet flushing etc. While you probably have an "open" system, I don't think it is yet a certainty.

But yes, a bit of water hammer can certainly give your tattletale hand a kick. Even a vibration can move that hand. Tapping the guage can make that hand move.
 

Mj23

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I dont think a regulator would change the hammer except that you would likely set it lower than 75 psi and lower pressure generally means less hammer , that little bump shouldnt hurt .
Thank you for all the replies. Yes, I do believe that I have an open plumbing system. As far as I know, there is no backflow preventer valve at the water meter.

If 90 to 100 psi spike is not that worrisome, at what pressure spike, would you begin to worry and think about a pressure reducing valve? 120? 130?

All this is an issue because I have had a slab leak within the last six months, and I have the clear Uponor pex pikes approximately 12 years old, which, in some instances have had mass failures.
 

Reach4

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If 90 to 100 psi spike is not that worrisome, at what pressure spike, would you begin to worry and think about a pressure reducing valve? 120? 130?
You presume that the pressure spike is external, rather than internal. It well could be, but it could be internal too... when you run your dishwasher, for example.
 

Mj23

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Even if it is internal, and it may well be, is a spike up to 100 psi something to worry about? At what range do you start to worry? And what should be done about it?
 

Reach4

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I say 130, which is a tad under what Watts says/implies in their sizing for a thermal expansion tank. Did you look at that first link in #7? The limiting factor is that you don't want the pressure to be high enough to send water out of the T&P, which is a nominal 150 psi. The other link in number 7 has similar info.

Now others disagree on this, and that is fine. I have presented my case. If they think they could keep the pressure under 80 in a closed system, they would find they would need unusually large thermal expansion tanks. A disagreement on this matter is healthy, and I understand there are good arguments. To summarize mine, hard sticking to 80 psi and less gives huge sizes for thermal expansion tank. The argument on the other side is that the code says .... Good point.

While I continue to think I would not put in a PRV in your case, I will point out that there is such a thing as a bypass PRV. That is like a check valve parallel to the PRV, which feeds water backwards if the inside pressure gets sufficiently higher than the incoming pressure.

If something in your house lets go before 150, it is usually going to be a float valve in a toilet. This is non-destructive, with the pressure being relieved by water going down the toilet overflow. They used to sell fill valves with this as an intentional feature: limit thermal expansion pressure by releasing water. Then people got concerned about wasting water, and the pressure relief valves for thermal expansion became less common. Thermal expansion tanks became the preferred way.

Now I am not saying that flex lines are not more likely to fail at 130 than at 50 psi,
With an open system today, don't presume that will continue. It used to be that almost all systems were open. As water systems change meters etc, they often add a check valve into the system.
 

Mj23

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Fantastic. I am going to hold off on the pressure reducing valve.

Now regarding the expansion tank:

I have two brand new 50 gallon tank water heaters. My plumber installed a 2 gallon expansion tank, Everbilt brand, set to the factory pre-charge of 40 psi.

Going by your expansion tank guide, I need a 4 gallon tank set to approximately 70 or 75 psi, which is the incoming water pressure.

I discussed this with my plumber, who had no idea about any of this. He says that he has installed several expansion tanks and never changed the factory pre-charge. however, he is willing to do anything that I ask him to do, including install a new expansion tank.

does it make sense to have a 4 gallon expansion tank set to a pre-charge of 70 to 75 psi?
 
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