Is an expansion tank needed for my new water heater?

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Lanmark79

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Hello, I'm Lanmark, I came across this cool plumbing forum and
it certainly looked like a great forum to get some good advice on plumbing..

So I just installed a new electric water heater, and I have my house psi set to 52 from my PRV.

I have my new water heater, a 38 gallon set to 130 F on both thermostats.

I'm connected to the city main water. I suspect that my PRV is about 15 years old. My house was built in 1988 I think. I do not have a expansion tank installed, but I'm thinking that I need one.

I tested my house pressure after not having any of my foucets on for over an hour, and I started on 50 but it slowly kept climbing all the way to 62-65 psi! Until I opened a kitchen foucet, then I fell back down to 50 psi.

I currently notice small bursts of pressure running when I first turn on my foucets, then it quickly decipates.
I used my outside hose foucet, with a Watts pressure gauge to check my house pressure. My hose foucet is connected to my closed pipping system..now, do you recommend that I get an expansion tank, and probably go and also replace my PRV with a new one as well? This is what I'm thinking, but I want to be sure before I go spending money on more stuff for my water system.

Someone said on another forum that if my gauge only goes up to 60 psi, I probably don't need an expansion tank. However, it was climbing above 60 psi before I turned a foucet on. Which had me concerned some.

Plus the fact that my T&P valve is literally my only safegaurd from having my water heater turn into a bomb, with my brother living right on top of where it is sitting, if it were to blow up.

Thanks in advance for any advice or tips you guys can give me.

Update: I just checked my house pressure again, after not having the water used for about 30 minutes, and my pressure gauge read a good 66 psi with no climb, which isn't too bad actually.
 
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Reach4

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I'm connected to the city main water. I suspect that my PRV is about 15 years old. My house was built in 1988 I think. I do not have a expansion tank installed, but I'm thinking that I need one.

I tested my house pressure after not having any of my foucets on for over an hour, and I started on 50 but it slowly kept climbing all the way to 62-65 psi! Until I opened a kitchen foucet, then I fell back down to 50 psi.
You probably need one. To see the pressure gauge climb, take a hot shower or bath, immediately turn off the faucets, and leave the faucets closed for a half hour.

If the water pressure only climbs to 90, then your PRV must be a bypass PRV and the water presssure is maybe 80, but then do you even need a PRV?
 

Lanmark79

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Okay, thanks for the tip, I will try that.
I have the NR3XL PRV, which I'm pretty sure has a built in bypass.

I'm on city water and there is a meter, and probably a check valve installed, so I definitely need one.

Anyway, having a bypass could explain why on our older water heater, the T&P valve never leaked, but eventually just flooded from the bottom.
 
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