water heater pressure


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Old 05-31-20, 12:23 PM
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Unhappy water heater pressure

what should the pressure be at the drain valve of my water heater when no water is flowing in the house? currently it is at 140 psi (no water flowing) with kitchen sink on it is about 50 psi. I had a leaky T&P relief valve so I replaced it but it still leaks randomly and sometimes constantly.What am I missing? BTW, I have 140 psi at water bid on outside of the house.
 
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Old 05-31-20, 01:16 PM
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Welcome to the forums.

The pressure at the bottom of the water heater should be the same as the rest of the house.
140psi is too high for water pressure. 60-70psi would be max.

You should look into a whole house PRV (pressure reducing valve).
If you install one then it would be recommended to install a pressure tank on the cold water side leading to the water heater.
 
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Old 05-31-20, 01:36 PM
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Hi Pete. Thank you for the greeting. I do have a prv installed. I turn the screw clockwise and counter-clockwise but it does not change the pressure at the water heater drain or outside bid with no water flowing (still 140 psi). but refilling the toilet tank the psi drops to about 20 psi or if i run the kitchen sink it drops to about 40 psi at the water heater. does it sound like the pressure reducing valve is faulty and would I still need to install a pressure tank if I have the prv already?
 
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Old 05-31-20, 01:52 PM
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You need to adjust the valve one turn , let the water run to settle the pressure and then check it.
Turning the adjustment in raises the pressure.

Many PRV valves don't allow water to flow back into the system. You could check and see if yours does. If acts like a check valve... you'll need a pressure tank.
 
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Old 05-31-20, 02:36 PM
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Hmmm...ok. in your opinion, what would be an honest rate to have a pressure tank installed?
 
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Old 05-31-20, 04:37 PM
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If you let out about a gallon of cold water from any faucet, does the pressure always go back to 140 PSI within 10 minutes? Try at several random times.

 
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Old 06-01-20, 07:55 AM
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Hi Allan,

yes it does go back to 140 psi.
 
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Old 06-01-20, 11:20 AM
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yes it does go back to 140 psi.
Replace the PRV and install a thermal expansion tank.
 
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Old 06-01-20, 08:16 PM
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ok on the PRV. is there a difference between a thermal expansion tank and installing a pressure tank on the cold water side that Pete mentioned in his post above?
 
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Old 06-02-20, 07:25 PM
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ok on the PRV. is there a difference between a thermal expansion tank and installing a pressure tank on the cold water side that Pete mentioned in his post above?
 
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Old 06-03-20, 05:11 AM
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No difference. The thermal expansion chamber and a pressure tank are the same thing, the most modern versions have a bladder inside so the water does not absorb the air cushion inside.

Every new tankful into the water heater will expand when heated. The expansion tank is used to prevent a significant pressure rise over and above what it was (140 PSI?) an hour before possibly tripping the temperature/pressure relief valve on the water heater.

A two gallon expansion tank is more than enough for a household water heater while a tank of at least 30 gallons is recommended for a well pump water system.

Some pressure reducing valves will prevent back flow into the water main as a way of relieving pressure from expanding water. This increases the need for an expansion tank although the function of the PRV is separate from the function of the expansion tank.
 
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Old 06-03-20, 01:57 PM
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Thank you kindly Allan. I appreciate the explanation.
 
 

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