New 2 gallon expansion tank factory set to 40psi and circulation pump

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Strider518

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I just finished installing a new expansion tank (factory set at 40 psi) for my natural gas water heater. I use a Grundfos type UP 15-10 B5 circulation pump. Other markings on the pump label are: P/N 59896213 P1 and what looks like a mathematical formula: I 1/1(A) with the number .22 below it. And P1(W) with the number 25 below it.
Do I need to change the pressure on the expansion tank?
BTW my street water pressure is about 50psi.
Thanks.
 

LLigetfa

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BTW my street water pressure is about 50psi.

I did an actual test at a garden hose faucet: 65 psi.
So then your street pressure is not 50. Do you have a PRV or does the pressure vary? Maybe there is a PRV and the outside hose bib is plumbed before it. Test at the HWT draincock to see if it reads the same as at the hose bib.
 

Michael Young

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I just finished installing a new expansion tank (factory set at 40 psi) for my natural gas water heater. I use a Grundfos type UP 15-10 B5 circulation pump. Other markings on the pump label are: P/N 59896213 P1 and what looks like a mathematical formula: I 1/1(A) with the number .22 below it. And P1(W) with the number 25 below it.
Do I need to change the pressure on the expansion tank?
BTW my street water pressure is about 50psi.
Thanks.
set the tank pressure to 50psi
 

Strider518

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Hello to all, and thank you for your advice. So, here's what I did, (with pressure at a cold water hose bib at 65 psi):
1.Hot water tank up to temperature.
2. Circulating pump running.
3.I opened one hot water tap at the kitchen sink.
4.I pressurized the expansion tank to 65.
 

Jeff H Young

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never run circ pump with water turned off and a faucet open . it could suck dry. otherwise good job!
 

GReynolds929

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Measured pressure needs to be static pressure (IE: no water running in system) shut water off the water heater (turn off power if electric) open a faucet or the T&P to relieve pressure and leave open. Add air in expansion tank to match measured static pressure. Ideally the expansion tank would be removed and reinstalled, but can be done without removing. Not sure why recirculation was running or making sure water heater was at temp.
 

Strider518

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Thanks to all again for the advice. Forums like this are (at least) worth the cost of a plumber's service call. I remember a cartoon from about 30 years back where there was a picture of two men: One was obviously a Plumber, and the other one was a Banker, with the background implying there were in a bank. The Plumber was handing money to the Banker. The caption read something like this: "The fellow on the left is a plumber, and the one on the right is a plumber too."
Here is a better description of when and how I pressurized the expansion tank.
1. I measured 65 psi at a garden hose bib. There were no open faucets, hot or cold, anywhere in the house.
2. When I got ready with my air compressor and tire pressure gauge
3. The water heater already in use, was up to temperature
3. The circulating pump was already on according to its control
4. I opened one hot water tap
5. I pressurized the expansion tank
I can remove the expansion tank and start over if necessary. I'm the home owner and retired, so I've got time. I like doing things like this and want to do them right.
 

Reach4

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When you measure or fill the connected expansion tank precharge air, the water pressure should be near zero.
 
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