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How to Remove Lime From a Hot Water Heater

Misty Amber Brighton

Preventive maintenance is key to a longer life of your hot water heater. Poorly operating heaters will produce water that is not as hot as you prefer it. Bad maintenance can lead to faulty elements, higher utility bills and a shorter life for your tank.

Lime deposits are often a cause of faulty hot water heaters, so removing lime deposits will save you money in the long run.

  1. Turn off the breaker to your hot water heater. Place a piece of tape over the breaker to make sure no one turns it back on while you are working. If you have a gas water heater snuff out the pilot light. Shut off the water supply to the water heater by using an adjustable wrench.

  2. Turn on a hot water faucet at about half strength to vent the hot water heater. Leave this faucet running for the time. Open the drain valve at the bottom of the heater tank by turning the valve counter-clockwise with adjustable wrench until a small amount of water trickles out of the valve.

  3. Attach a garden hose to the drain valve and hand tighten. Place the other end of the garden hose into a nearby sink or bathtub drain. In order for the water to drain properly, the hose should slant downward, not upward. Make sure there are no kinks in the hose. Allow the water heater tank to completely drain, which should take about 30 minutes for a 40-gallon tank. Once the tank is empty turn off the hot water faucet.

  4. Locate the anode rod, which is a large recessed bolt on the top of your hot water heater tank. Your anode rod will likely be secured with a hex head screw that is around 3/4 inch. Use an Allen wrench to remove this screw. Take the anode rod completely out of the water heater.

  5. Pour 3 to 4 gallons of apple cider vinegar into the hot water heater. Apple cider vinegar, unlike white vinegar, has an acidic value that is known to dissolve lime. Allow the vinegar to sit in the hot water heater for a period of at least 24 hours; longer if the tank is severely caked with lime but don't exceed 48 hours.

  6. Open the drain valve to allow the vinegar solution to drain out of the tank. Check the hose periodically for large chunks of lime. Once the tank has completely drained of the vinegar, clean the anode rod by wiping with apple cider vinegar and re-insert. Check the drain valve for any leftover pieces of lime deposits and whisk away with a soft toothbrush. Once the tank is empty and all lime is removed, close the drain valve.

  7. Turn on a hot water faucet again to vent the system. Turn the water supply back on. Allow the tank to fill until you first notice signs of water entering the tank, which will take about five minutes. When this occurs shut off the hot water faucet. Completely fill the tank before turning on the breaker to the water tank or lighting the gas pilot.