Tank. Volume. (Gallons). Max. Accept. Volume. (Gallons). A. Diameter ST 8. ¾ NPTM. 5. ST 9. ¾ NPTM. 7. ST For larger applications: Visit , download the AMTROL App or contact Technical. AMTROL ST (Therm-X-Trol) is a water heater expansion tank, designed for use in domestic hot water heating systems to eliminate the potential hazards of. Amtrol STV THERM-X-TROL Expansion Tank, Gallon (N) - Water Heaters - Back. Amtrol ST Thermal Expansion Tank.


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The only way to be sure is to test it yourself. It simply attaches to your system anywhere that a hose would connect and tells you the water pressure at the fixture.

Additional Information

To test the pre-charge of your expansion tank, all you need is a standard tire pressure gauge. My tire gauge has a bleeder valve, which makes removing excess pressure really easy.


Open the drain valve all the way. Take note of the water pressure. Mine at the Utah house is 60 psi: Imagine, for example, that you want to check the air pressure of a yoga ball.

Amtrol STC Therm-X-Trol Thermal Expansion Tank

This photo shows it closed: Cold water valve turned off 2. Keep it open throughout this procedure. If you amtrol st-12 expansion tank a hot water recirculating pump, turn it off and close the valve on the return line: Turn off the recirculating pump and close the return valve 5.

Connect a drain hose to the drain valve of your water heater the same valve amtrol st-12 expansion tank you tested the water pressureand open the valve all the way.

THERM-X-TROL ST Expansion Tank - -

Do a slow count to 10, then close the valve. Partially drain your water heater to relieve water pressure With the water pressure relieved, you can now get an accurate reading from your tank.

But, if you get no pressure reading from your tank which is what happened to me todaythen that probably means the diaphragm in your tank has ruptured or otherwise failed, meaning your expansion tank needs to be replaced.

Amtrol st-12 expansion tank was my zero pressure reading today: Generally, you should replace the old expansion tank with a new one of the same size. Going bigger is fine — going smaller is not.

ST-12 Therm-X-Trol Inline Thermal Expansion Tank (4.4 Gal)

You can also find them at Home Depot, Lowes, or amtrol st-12 expansion tank local hardware store. The original installing plumber had actually used the smaller tank size in this house, so I figured this was the right time to correct that mistake and go one size bigger.

Next, I removed one side of the support strap that was helping to amtrol st-12 expansion tank the old tank in place it was screwed into the ductwork overhead.

Your unit may not have a support strap it only needs one if the tank is installed horizontally. Remove old support strap Third, I placed a towel on top of the water heater, underneath where the expansion tank connected to the cold water line.

Since the failed tank is likely full of water, be ready for it to spill. Overview What Is Thermal Expansion?

With modern amtrol st-12 expansion tank codes mandating backflow prevention, thermal expansion can cause pressure buildup in domestic water systems. When demand is put upon a potable water system, hot water is drawn from the water heater.

Cold water from the supply line enters the water heater to replenish it.


The cold water is heated to replace the hot water used.