How to Chlorinate a Water Heater

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Learn how to chlorinate a water heater properly, to eliminate the unpleasant odor or black water problem. Chlorination is a simple but delicate process. It can be done either by using the continuous chlorine feeder, which provides 100% efficiency in fixing these problems, or by flushing with the common household bleach, periodically.


Step by step guide for proper chlorination of water heaters

  • Before chlorination takes places, it is imperative to turn off both electrical and gas supply to water heater.

  • Also close the water supply to the heater on the main shut off valve.

  • Since the water inside the heater’s tank is still hot or warm, there is a buildup pressure that has to be reduced. Open the closest hot water tap and temperature and pressure relief valve (T&P) valve, located at the top of the unit.

  • Locate the drain valve at the bottom of the heater, connect one end of the garden hose to the valve and the other end to the drain. Drain enough water to compensate the amount of chlorine you are planning to put in. More about draining here.

  • For chlorination, use the household bleach and put it in the water heater tank. The best way to do it is through the opening where the T&P, anode rod or hot water inlet are located. Use the pipe wrench to remove the T&P valve, anode rod or hot water outlet pipe, all located in the upper part of the unit.

  • For every 30 gallons of water put one gallon of bleach, through one of the recommended openings. If the water heater has a capacity of 60 gallons, use 2 gallons of bleach. Close the opening that you used for putting the chlorine in.

  • Open the closed water inlet valve to fill the tank. When the tank is full, close the valve.

  • Let the bleach stay inside the water tank for at least one hour.

  • Now, open the hot water faucets and let the water/bleach mixture run out, so it cleans the hot water lines.

  • Use the bottom drain valve; connect the garden hose to flush the remaining bleach mixture from the storage tank.

  • Close the drain valve and fill the tank with fresh water. Let it stay for at least 15 minutes.

  • Purge all the air from the hot water supply line and drain the water from the tank through the drain valve. Close the faucet.

  • After you have drained all the water from the tank, check the anode rod to see is there any deterioration. Replace the anode if it is needed.

  • Turn the electric switch ON, including the gas supply to the water heater.

  • Resume the water heating.

  • The bad odor should now be eliminated.

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