How to Bleed a Water Expansion Tank

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Things You'll Need

  • Bucket

  • Adjustable wrench

One of the methods used to heat homes is a hot-water heating system. This type of system consists of running pipes that contain hot water from your boiler through the rest of your house. The heat is distributed through baseboards along the floor or radiators. As the water cools, it is returned to the boiler to be reheated. One of the components of a hot water heating system is an expansion tank. As water heats up, it expands, putting pressure on the pipes and the hot water tank. The expansion tank is a pressurized tank that the heated water flows into to relieve the pressure in the hot water system; as the water cools, the pressure returns it to the system. As part of your routine maintenance, you'll need to drain the tank once or twice a year.


Step 1

Turn the boiler off, and wait a couple of hours to let the water cool down. Find the shutoff valve and the drain valve on the expansion tank. (The shutoff valve goes into the furnace; the drain valve is on the bottom of the tank.) Close the shutoff valve.

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Step 2

Put a bucket or large container underneath the drain valve and open it. The water should flow into the bucket. If the water doesn't begin to drain, use an adjustable wrench to open the vacuum-breaker plug (located on the drain valve).


Step 3

When water stops draining into the bucket, close the drain valve (and vacuum-breaker plug, if you opened it) and reopen the shutoff valve.

Step 4

If you're bleeding your whole system, proceed to bleed the radiators. If you're just bleeding the expansion tank, turn the boiler back on.


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