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[Merged thread] Marvin: Whirlpool 30 gal gas water heater 9-10 years old

[Merged thread] Marvin: Whirlpool 30 gal gas water heater 9-10 years old


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Old 12-14-13, 09:10 PM
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Cool [Merged thread] Marvin: Whirlpool 30 gal gas water heater 9-10 years old

Recently had piping replaced due to freezing. Repaired all piping to both sides hot and cold. Drained the tank to let out all the air. Turned on the water from the meter, which i found out the pressure at the meter was over 180psi. Also had replaced p.r.v. Set at 40 psi.
Before even having an opportunity to light the burner, the pop off t&p
valve kept popping off. I then bought a 2.1 gal type expansion tank xt-8. Also replaced t&p valve. It still pops off even after i drained the tank and started all over. I have been in the plumbing trade and industry before for over 18-20 years. What is wrong!!! Perplexed!!!
 
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Old 12-14-13, 09:44 PM
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Cool Water pressure@water heater

If the pressure at the meter is over 150 psi. And the pressure reducing
valve is set at 40 psi and it is in the cold water line before the heater, what is the pressure of water when filling the tank?
 
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Old 12-14-13, 10:48 PM
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Is there a valved bypass around the pressure reducing valve? If yes then the bypass valve may be leaking. Otherwise I would suspect the PRV itself is leaking.
 
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Old 12-14-13, 10:48 PM
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If the T & P valve was releasing water without even heating it then the water pressure must be too high.

I've never heard of over 180psi water pressure in a house. Are you sure the PRV is actually working now ?
Have you rechecked the water pressure recently ?

I believe the T & P valve releases water at 180f or 150psi.
 
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Old 12-14-13, 11:00 PM
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Forty psi, assuming that there is no leaking through the PRV or an external bypass valve arrangement. A water heater that has no expansion tank could raise the pressure by thermal expansion from the initial cold fill to operating temperature enough to open the safety valve.
 
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Old 12-14-13, 11:51 PM
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I believe the T & P valve releases water at 180f or 150psi.
While temperature & pressure safety relief valves can be obtained with several different pressure ratings the most common ones are 150 psi and 210 degrees F. I don't think I have ever seen one with a temperature rating other than 210 degrees F.
 
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Old 12-15-13, 06:08 PM
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Cool Lowery:added note

The water heater has a 40 psi expansion tank installed before the cut off in the cold water supply on top of the heater. It is a 2.1 gal
xt-8 precharged at 40 psi. The t&p valve is 150 psi, 210 degree normal
watts 100xl. Thereis no other valve between the prv and the cold water cut off. There is an emergency gate valve cut prior to the prv.
 
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Old 12-15-13, 06:17 PM
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Lowery41:added

The pressure by the gauge reads 38-40 psi upon open the outside hydrant, which is right by the prv under the floor. Therefore i presume the pressure is 38-40 in the house. When the hydrant is turned off the pressure builds back up to 180 plus, the gauge only reads 180psi. I have talked to a rep. From the water company, he says several people have installed a second prv. I have been thinking about placing one in front of the one installed at 40 psi and set the other one at 65-70 psi.suggestions!! also the rep said they have placed a vaccum breaker or back flow peventer on the meter.
 

Last edited by LOWERY41; 12-15-13 at 06:25 PM. Reason: SPELLING CHANGE AND COMMENT
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Old 12-15-13, 06:31 PM
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you are correct this one is 210 degrees. i hope i did not mislead anyone on that.my apologies.
 
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Old 12-15-13, 10:16 PM
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If your pressure gauge is reading 40 psi when the water is flowing but jumps to 180+ when the water is not flowing then the PRV has an internal leak. Rebuild kits are available but they cost about 70% of what a new PRV will cost and there is NO guarantee that the rebuild kit will fix the problem. In other words, you need a new PRV.

Second issue is that an expansion tank needs to have the same static air pressure (air pressure when no water pressure) as the nominal water pressure.

Try connecting the pressure gauge to a tap inside the house such as the laundry connection or even the drain on the water heater. Open the valve slightly (laundry or WH drain) to read the static water pressure and then turn on a faucet somewhere in the house to read the dynamic pressure. It is normal for the dynamic pressure (pressure when water is flowing) to be a little less than the static pressure but not by a whole lot. Turn off the faucet and observe the static pressure again. With the PRV set at 40 psi static the dynamic pressure might drop as low as 35 psi and should rise back to the 40 psi mark when the water flow ceases. Anything else and your PRV is the most likely problem.
 
 

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