Expansion Tank Pressure Test

The hot water expansion tank is a two gallon tank that hangs off of your hot water system or your boiler.

Expansion tank pressure test.

Release or add air as necessary to make the pressure 2 psi below the pressure switch pump cut in setting. The test is also designed to be used on a typically sized pressure tank not on an oversized tank. Pressure test the cap with a professional pressure testing device follow manufacturer s instruction. For example if your well pump pressure control switch is set to cut in start pumping water from the well at 30 psi then set the pressure tank to 30 2 28 psi.

It is used to absorb excess water pressure. Use a bicycle pump or compressor to fill the tank to match the system pressure you noted earlier. If the pressure setting reads less than 12 psi it probably will since you drained water from the tank attach an air compressor or hand air. But there are some circumstances in which an adjustment to the pre charge may be needed.

A properly sized and charged tank is designed to keep the system pressure about 5 0 psi lower than the pressure relief while the system is at maximum operating temperature. Most home pressure tanks have on average about a 5 gallon draw down or supply of water. Heating boiler bladder type expansion tank compression tank pressure adjustment. Bleed air pressure out of the water tank or add air pressure into the water tank until the tank pressure is at the desired set pressure.

When water is heated or a hot water faucet is turned off abruptly pressure builds from expanding water molecules. With the water pressure relieved you can now get an accurate reading from your tank. When the pre charge was not to factory specifications when the air pre charge pressure needs to be increased to. Check pressure in the tank with your pressure gauge.

Air can be added with a compressor or bicycle pump. Most expansion tanks require a psi reading of about 12 psi. These tanks are usually 2 to 3 in height. If the pressure is less than 12 psi you will need to add some air s add air.

Always check the radiator expansion tank when replacing a faulty cap. Check your manual for the precise rating for your expansion tank. Use a tire gauge to check the pressure. Expose the schrader valve same valve you d find on a bike or car tire on the bottom of the expansion tank you may have to unscrew a plastic cap and firmly press your tire pressure gauge against the valve to get a reading.

If the cap fails to hold the rated pressure replace the cap. Determining the air side charge of an expansion tank in a hydronic heating system is a relatively easy task. Start by removing the protective cover from the air valve on the tank. For example if you have a pressure switch setting of 30 50 psi you pressure measured at the top of the tank should read 28 psi.