Expansion Tank Pressure Test

Heating boiler bladder type expansion tank compression tank pressure adjustment.

Expansion tank pressure test.

Check pressure in the tank with your pressure gauge. When water is heated or a hot water faucet is turned off abruptly pressure builds from expanding water molecules. Check your manual for the precise rating for your expansion tank. 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.

Air can be added with a compressor or bicycle pump. If the pressure is less than 12 psi you will need to add some air s add air. When the pre charge was not to factory specifications when the air pre charge pressure needs to be increased to. Most expansion tanks require a psi reading of about 12 psi.

Pressure test the cap with a professional pressure testing device follow manufacturer s instruction. The hot water expansion tank is a two gallon tank that hangs off of your hot water system or your boiler. Most home pressure tanks have on average about a 5 gallon draw down or supply of water. Most expansion tanks come pressurized to 12 40 psi but before you install the tank you have to match the system pressure.

It may have caused a dangerous build up of overpressure causing bursts or cracks which ultimately lead to. 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. 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.

Use a tire gauge to check the pressure. Use a bicycle pump or compressor to fill the tank to match the system pressure you noted earlier. These tanks are usually 2 to 3 in height. 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.

Determining the air side charge of an expansion tank in a hydronic heating system is a relatively easy task. For most installations the factory set air pre charge in an expansion tank is correct and should be left alone. Start by removing the protective cover from the air valve on the tank. 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. It is used to absorb excess water pressure. 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. 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.