Why doesnt Thermal Expansion Tank work?

[keith melling]

Having experienced the symptoms of classic thermal expansion, water coming out of Hot Water Heater relief valve, we installed an Amtrol 4 gal tank on our new 50 gal heater. The incoming street pressure is about 180. After installing the tank, we are still having water drip out the relief valve. A pressure gauge on the water heaters drain reads 150, drops to 75 when a toilet is flushed, then slowly works its way back up to 100-130, back down again when water is used. Is this the way the expansion tank is supposed to work? We were led to believe there would be no pressure build up and no leaking once the tank was installed. Also, whenever the pressure exceeds 110 or so, flushing a toilet causes a loud groaning noise when first the toilet inlet opens to bring in water. It stops fairly quickly. It does not happen again until the next flush with pressure over 110. We even tried a second expansion tank with the same results. Are we doomed to forever wasting gas and water?

[RichParticipant]

: Having experienced the symptoms of classic thermal expansion, : water coming out of Hot Water Heater relief valve, we installed : an Amtrol 4 gal tank on our new 50 gal heater. The incoming : street pressure is about 180. After installing the tank, we : are still having water drip out the relief valve. A pressure : gauge on the water heaters drain reads 150, drops to 75 when : a toilet is flushed, then slowly works its way back up to : 100-130, back down again when water is used. Is this the way : the expansion tank is supposed to work? We were led to believe : there would be no pressure build up and no leaking once the : tank was installed. Also, whenever the pressure exceeds 110 : or so, flushing a toilet causes a loud groaning noise when : first the toilet inlet opens to bring in water. It stops : fairly quickly. It does not happen again until the next flush : with pressure over 110. We even tried a second expansion tank : with the same results. Are we doomed to forever wasting gas : and water?Answer, The T&P on the tank is set for 150 PSI. Plumbing code calls for a pressure reducer on the main water supply line if the pressure is over 80 PSI. You can buy these at the local hardware store for $75.00 for a 1 inch model.You will find that everything will last longer with the reduced pressure.

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