Expansion Tank Pressure

Start by removing the protective cover from the air valve on the tank.

Expansion tank pressure.

It is used to absorb excess water pressure. The key concepts are. The hot water expansion tank is a two gallon tank that hangs off of your hot water system or your boiler. This is where expansion tanks come in.

Use a tire gauge to check the 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. You re good to go. Check your manual for the precise rating for your expansion tank.

Heating boiler bladder type expansion tank compression tank pressure adjustment. For example water heated from 90 f to a thermostat setting of 140 f in a 40 gallon water heater will expand by almost one half gallon. Expansion tanks are used to absorb any excess pressure created due to thermal expansion which prevents an over pressurization of the system. Most expansion tanks require a psi reading of about 12 psi.

If the pressure is less than 12 psi you will need to add some air s add air. If the expansion tank s pressure is lower than your house s water pressure you ll need to fill the tank to the matching pressure using the same type of air compressor you d use to re inflate your car s tires. This increases the overall water volume and pressure inside the tank which must be relieved to avoid the potentially negative effects of thermal expansion. A detailed procedure for sizing diaphragm type expansion tanks is given in reference 1 as well as several other industry publications.

For example if a 15 gal. Pressure and air vents. Pressurizing the air side of the tank to equal the static pressure of the water at the expansion tank location and before adding water to the system. But there are some circumstances in which an adjustment to the pre charge may be needed.

If your pre charge was set properly or only needed a minor pressure adjustment then hooray. 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. When water is heated or a hot water faucet is turned off abruptly pressure builds from expanding water molecules. In any situation where water in a closed system is heated an expansion tank is required.

Irc 2009 p2903 4 thermal expansion control. Most expansion tanks come pressurized to 12 40 psi but before you install the tank you have to match the system pressure. Tank is hanging from the ceiling replace it with a no. 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.

For most installations the factory set air pre charge in an expansion tank is correct and should be left alone.