Pressure Relief or Expansion Tank Problem


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Old 09-06-06, 10:56 AM
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Pressure Relief or Expansion Tank Problem

Here's what happens. Everytime someone takes a shower, about 5 or 10 minutes later if we go to use a faucet anywhere else in the house the water comes shooting out with very high pressure. Is this a bad pressure relief valve, expansion tank or both? It's a Rheem Professional 50 tank (about 5 years old) and a Therm-X-trol ST-12 expansion tank probably 15 years old.
Thanks.
 
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Old 09-06-06, 11:46 AM
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It is not a problem with the pressure relief valve (properly called a Temperature and Pressure relief valve or T&P valve) nor is it likely a problem with the expansion tank.

Most likely it is a sticking pressure regulating valve, also known as a PRV.

The PRV reduces the (too) high pressure from the street main to about 60-80 psi for use in the house. It normally is located immediately after the main shut-off valve for the entire house.
 
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Old 09-06-06, 11:47 AM
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Wink

Id say check the tank for sure see if you get water out of the schrader valve on it.
takes a shower, about 5 or 10 minutes later if we go to use a faucet anywhere else in the house the water comes shooting out with very high pressure.
When you take the shower cold water refills the hot water tank. In a little bit the water there gets hot and it expands. So if your Therm-X-trol ST-12 expansion tank probably 15 years old.
Bladder is shot thats what you will get. The PRV on the water heater is ok

ED
 
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Old 09-06-06, 04:47 PM
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Ok so one of you thinks it's the PRV coming off the main and the other thinks it's a bad bladder in the expansion tank. What is the best way to test and find out the difference? I'll let you know plumbing is not my strong suit.
 
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Old 09-06-06, 05:10 PM
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check the air tank see if you get water out of the schrader valve thats like a tire valve on the tank. Or turn the water off to the home open some of the shut offs . The tank at the schrader valve should have a PSI of 2 lb lower that the water psi in in the home when its on.

Therm-X-trol ST-12 expansion tank

probably 15 years old. Ill bet on the tank bladder

ED
 
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Old 09-06-06, 07:24 PM
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Ok, I pressed in the schrader valve (the one on the bottom of the expansion tank) and there was no air or water or nothing that came out. Now what?
 
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Old 09-06-06, 09:11 PM
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I pressed in the schrader valve (the one on the bottom of the expansion tank) and there was no air or water
If this was with water off put air in in now see if you can

Does it say on the tank what the psi should be?? If not try 50lb of air in it. Then turn the water back on in the home
The book say Therm-X-Trol tank ST-12. Designed to accept increased water volume created when storage tank is heated keeping system pressure below relief valve setting

ED
 
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Old 09-06-06, 10:39 PM
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I'm just adding on to what Ed Imeduc said. When you go to pressurize the bladder turn off the main water shut off and open a faucet so there will be no pressure in the system when filling the bladder or else youíll not get the right amount of air in it. In a month youíll want to check the pressure in the bladder and see how fast itís losing psi. Again when you go to check the pressure make sure to shut off the main and open a faucet to get an accurate reading.
 
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Old 09-07-06, 03:56 AM
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Ok, I will try those steps sometime in the next few days and then report back on my progress. Thanks!
 
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Old 11-13-06, 04:56 AM
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Talking Problem finally fixed

OK, well it only took me 2 months to get to work and finish the job! I probably would have waited longer but my wife pointed out a water stain on the ceiling of our kitchen where the toilet upstairs was leaking because of the pressure build-up. Yes, it was the expansion tank. It took me about 2 hours to get the old one off with a lot of elbow grease, hammering and WD-40. It was really corroded onto the pipes. The old tank was full of water and little black shreds of the old bladder. I installed the new tank and no more pressure build-up problems after a hot shower! Thanks for helping me figure-out the problem and fix it myself!
 
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Old 04-16-14, 03:40 PM
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Recently bought a house with the Therm X Trol st-5 expansion tank already installed, have been here for several months now and it suddenly started making noise, like escaping air. Checked the air pressure, right at 50. Water comes out of the valve when checked, no air leaks at any of the fittings... notta clue, any suggestions?
 
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Old 04-24-14, 05:29 PM
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Water comes out of the valve when checked, no air leaks at any of the fittings... notta clue, any suggestions?
What valve does the water come out? If it's the schrader valve, the bladder in the tank has ruptured and the tank should be replaced.
 
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Old 04-28-14, 12:42 AM
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when I checked the air pressure in the tank, water came out of the schrader valve. So this is a simple fix then, thanks for your help.
 
 

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