The hot water in the units is provided by a 190 liters/50 US gal Hot Water Tank (HWT), heated by natural gas and vented externally. All units in the OGT have a Hot Water Recirculation Pump (HWRP) as part of the hot water system and most units who have installed new HWT also have an Expansion Tank. Unfortunately, the HWT have a shelf-life of 10-15 years. It is highly recommended that owners have water leak detectors in their mechanical rooms in case of a leaky HWT or pipe. Find options for leak detector sensors here.

Below is information about HWRP and HWET.

What is a Water Expansion Tank?

A Hot Water Expansion Tank (HWET) is a metal tank that has a poly bladder in the middle. One end of the expansion tank is connected to the cold-water inlet line going to the water heater. This end of the expansion tank will contain water and the opposite side will contain air.  Air compresses so when the water is heated it expands. The expanded water compresses the air in the expansion tank eliminating expansion in any water lines. The air end of the expansion tank will have a Schrader valve (the same as a bicycle tire). The Schrader valve has a plastic protective cap that can be unscrewed to access the valve.

Why do you need a HWET?

Water expands when heated and contracts when cooled. This expansion will cause Pex water lines, washing machine hoses and poly water lines to dishwashers and fridges to expand and contract. This expansion over time will cause the lines to crack and leak. To prevent this an expansion tank is installed on the inlet line of the water heater.

How do you know the expansion tank is working?

Testing the expansion tank to confirm it is working correctly can be done a couple of ways. One way is to tap the side of the expansion tank with a kitchen knife or a small metal object. The half of the tank containing water will sound solid. The half of the tank containing air will sound empty or tinny. If the entire tank sounds solid then briefly press the stem on the Schrader valve. If water comes out the Schrader valve the bladder has leaked and the expansion tank needs to be replaced.

What steps are needed to test an expansion tank?

Setting the proper air pressure in your expansion tank is critical and requires two steps. One is by installing a pressure gauge on the hose tap in the garage. This will tell you the water pressure of your unit. The second step is to close the main water valve (this is the valve you close when your unit is unoccupied). Also close the cold-water inlet valve to the water heater. Open a cold and a hot water tap at any sink and drain the water. When the water has stopped

flowing test the air pressure in the expansion tank with a tire pressure tester on the expansion tank Schrader valve. The pressure should be 2 to 3 psi lower than your system pressure. For example, if the water pressure at your hose tap in your garage is 65 psi then the expansion tank air pressure should be 62 to 63 psi. If the pressure is low it can be increased using an air compressor or a bicycle pump. If the pressure is high the stem on the Schrader valve can

depressed releasing the excess air. Checking the air pressure in the Expansion Tank annually is a good practice. If your water system does not have an expansion tank then contact a qualified plumber to make sure what

you have is eliminating water expansion.

Contributed by: Tom Dobrowolski