How to Drain a Waterlogged Expansion Tank on a Water Heater

An expansion tank is a safety feature often found on hot water heaters as well as on boilers used to heat homes. When water heats up, it expands, which puts high pressure on the tank in the boiler or the water heater. This weakens the tank over time, possibly causing it to burst. The expansion tank allows water to flow out of the main tank when it expands, relieving pressure on the tank. Some expansion tanks contain a rubber bladder that pushes the water back into the main tank as it cools, but if your expansion tank does not contain a bladder, it can become waterlogged. Draining it is a fairly easy maintenance task.

Garden hose
Bucket

Instructions

- 1
  Locate the pipe that runs between the water heater and the expansion tank.
- 2
  Close the valve on the pipe between the water heater and the expansion tank.
- 3
  Connect a garden hose to the drain valve on the expansion tank. Place the opposite end of the hose in a floor drain, a sink or a bucket. Take care when handling the water so you don't get scalded. Open the drain valve.
- 4
  Open the air valve on the tank when water starts to flow out of the hose. Depending on how your system is set up, the air valve will be located on the side of the expansion tank, on the drain valve, or on the valve between the water heater and the expansion tank.
- 5
  Close the drain valve and the air valve after the water has drained out of the expansion tank.
- 6
  Open the valve on the pipe between the water heater and the expansion tank.

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