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Draining and Flushing A Water Heater

Drain the hot water tank

drain flush hot water tank preventive maintenance 9-18-14Whenever you need to change an element in an electric hot water heater, leave the heater unused over a freezing winter, or when the heater needs cleaning, you will need to drain it, says the most reliable Littleton plumbing specialists.

You will also need to drain the water heater if it needs to be replaced.  For draining and flushing a water heater, you must open both its drain valve and the T&P valve, (or a hot water faucet in the house) to break the vacuum the water will pull as it drains. Without breaking the vacuum, some water will always stay in the heater.

Before draining an electric water heater, turn off the electric power at a cutoff switch near the heater or at the circuit breaker or fuse panel.  Throw the breaker (typically a 30-amp or 20-amp double pole) to the OFF position or remove both heater fuses.

Plumbing Pro Tip of the Week

Tip #1  For a gas heater, follow the manufacturer’s shut-down procedures printed on the side of the tank.  To keep water from coming back into the heater, turn the main supply valve off, too, normally at the valve on the cold side of the heater.

Tip #2  Attach a garden hose to the drain valve on the bottom of the heater and pull the opposite end of the hose outside the house or push it into a floor drain.

Tip #3  The hose end must be level with or below the bottom of the heater to allow all the water to drain out.

Tip #4  Open the T&P valve by lifting the lever or turn on a hot water faucet anywhere in the house.

Tip #5  Open the drain valve.

Tip #6  Let the heater drain completely, then close the drain valve and the T&P valve.  When refilling, to make sure the air gets purged from the tank so it can fill completely, open a hot water faucet in the house (if you haven’t already done so), and turn the faucet off when water begins to flow from it.  Then turn off the water coming into the heater.  Reapply the power to the heater.

Flushing a water heater

To flush a water heater, first drain the heater.  Leave the hose attached to the drain.  Then turn the water heater valve back on in spurts (full on for a few seconds and then off) to dislodge as much debris as possible in the tank bottom.  Do this at least a dozen times.  Observe the drain hose end for muddy water and debris.  Refill the heater when the hose runs clear.

PLUMBING TRADE SECRETS:  Hard water can build scale that reaches the bottom element in just a few months.  If you don’t drain the heater, the element will be covered by the scale and burn up.


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