Whether you have a tankless water heater or a standard water heater, they can develop limescale. Limescale causes rock layers to form on the tank bottom, which makes the heater run less efficiently. A water heater that has lime buildup commonly makes a popping or hissing noise. It is possible to remove the limescale by following these tips.
Prepare to Remove the Limescale
To flush limescale from the water heater, gather:
- rubber gloves
- scrub brush
- adjustable wrench
- garden hose
- wire coat hanger
- pipe compound descale solution
Shut off an electric water heater from the main electrical panel. For extra safety, test for a current with a multimeter.
To turn off gas water heaters, rotate the dial on the thermostat to "OFF." Locate the gas supply line, which is commonly on the side or behind the water heater, and rotate it clockwise.
Drain the Water Heater
Let the unit cool, and shut off the cold water supply, which is commonly located on top of the tank. If you have a tankless water heater, refer to your manual for valve location and flushing directions.
Open a nearby tap halfway, and rotate the drain valve on the bottom of the tank with an adjustable wrench, and wait for a small amount of water to drip.
Keep rotating the wrench left until it comes off the tank. Straighten a wire coat hanger, and insert the pointed end into the drain valve. Clean as much limescale as possible with the wire, and replace damaged valves. Attach the hose to the drain valve, and lay the other hose end in a sink or outside.
Ensure the hose has no kinks and slants down. Allow the water to drain, which commonly takes about forty minutes. If the water seems slow, shake the hose.
Clean the Tank
Find the anode rod, a recessed bolt, which is commonly on top of the water heater. Remove the hex screw with an Allen wrench, and store the parts in a safe place.
Fill the tank with three or four cups of apple cider vinegar. Apple cider vinegar has acid content that breaks down limescale, which white vinegar lacks.
Let the vinegar stay in the tank for twenty-four to forty-eight hours, but no longer than forty-eight hours. Set a bucket under the drain valve, and keep the drain valve open, so the solution will pour out.
Flush the tank with clean water to rid the system of vinegar and remaining lime scale. Check inside the drain valve opening for lime scale remnants, and scrape them with wire. Rub some pipe compound on the drain valve threads, and reinstall it.
Relight gas water heaters according to instructions in your manual. It is ideal to replace water heaters more than fifteen years old.