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How to Clean a Tank-Style Water Heater

February 04, 2016

Get the gunk out and get more life from the old heater

Calcium carbonate builds up at the bottom of the water tank and reflects the heat back against the glass lining. This reduces the efficiency of the heater and shortens its life.

Here’s how to clean it:

  • Turn off the heat source, either gas or electricity
  • Turn off the water supply to the heater
  • Attach a garden hose to the bottom of the heater, run the other end either to the outside or to a floor drain.
  • Open the T-slot in the water heater’s drain using a slotted screwdriver. You’ll hear it let go when it is opened.
  • Open the pressure relief valve to speed drainage. You’ll hear air rushing in when itr is open.
  • Drain the tank of water and some sediments.
  • Turn the water supply to the heater back on to forcibly flush the tank. This will force out all of the calcium carbonate that has settled into the bottom of the water heater.
  • Flush for about 20 minutes, then shut off the water supply.
  • Close the drain, disconnect the garden hose, reset the pressure relief valve.
  • Turn the water back on, turn on the water heater, and turn on the power.
  • Marvel at all of the junk that you removed from the water heater. 

 Cleaning the water heater this way each year can increase the life of the heater five years or more and prolong the day when you need to upgrade to an expensive high-efficiency unit.


—Mark Scott owns MARK IV Builders in Cabin John, MD. 


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