Water Heater Maintenance Checklist

The checklist

Tools and supplies

• Garden hose and a bucket, or a route to a floor drain
• Flathead screwdriver for a stiff drain valve
• Thick gloves and safety goggles
• A socket and breaker bar for the anode rod (see the anode section)
• For tankless: a descaling kit with a pump, hoses and solution, or white vinegar

Tank heaters: step by step

1. 1

   Cause 1: Flush the sediment

   Turn off the gas or the breaker, close the cold supply, hook a hose to the drain valve and let the tank empty. Then open the cold supply with the drain still open and keep flushing until the water runs clear. A.O. Smith says draining usually takes 20 to 40 minutes, longer with heavy sediment. Full details are on our how to flush a water heater page.

2. 2

   Cause 2: Test the relief valve

   Lift the T&P valve's handle and let it snap back. You should hear a gush of water into the discharge pipe, and it should stop cleanly. Put a bucket under the end of the pipe first. If the valve won't open, or keeps dripping after you let go, replace it. HomeGuide puts that at $50 to $300 professionally.

3. 3

   Cause 3: Check the anode rod

   The anode rod is a metal rod that corrodes so your tank doesn't. A.O. Smith's troubleshooting guide says to inspect it every year or as needed. If it's eaten down to the core wire or caked with scale, replace it. Our anode rod replacement guide walks through it.

4. 4

   Cause 4: Set the temperature

   A.O. Smith recommends 120°F for the balance of heating speed, energy cost and safety. Most gas valves don't show degrees, just a dial, so check the tap with a kitchen thermometer after the tank has recovered.

5. 5

   Cause 5: Gas models: look at the burner area

   Some gas water heaters have air screens at the bottom that need cleaning. A dusty laundry room clogs them fast. While you're there, look through the sight glass: a steady blue flame is what you want. Yellow, lazy flames or soot mean the burner needs a professional look.

6. 6

   Cause 6: Electric models: mostly hands off

   An electric heater has no burner or flue to clean, so flushing and the anode check do most of the work. Don't open the element covers unless you're troubleshooting, and only with the breaker off. If the water runs out faster than it used to, read up on elements and thermostats.

Tankless heaters: annual maintenance

Navien recommends annual maintenance and descaling at least once a year. Hard water, a higher temperature setting or heavy hot water use mean more often.

The job is a descale: isolate the unit, pump vinegar or a descaling solution through the heat exchanger, then flush it with clean water. Rinnai's procedure uses 4 gallons of undiluted white vinegar and says the flush may take up to 45 minutes. Navien lists the inlet water filter, the intake air filter and, on condensing models, the condensate trap as the other maintenance items. The full process is on how to flush a tankless water heater.

One warning from Navien: if service is done wrong and the heater is damaged, you could void the warranty. Read your manual before you start.

Mistakes to avoid

• Flushing a tank that hasn't been touched in years. The old plastic drain valve may not close again once sediment is stirred up. Have a spare drain valve or a hose cap on hand.
• Restoring power to an empty electric tank. The elements burn out dry. Refill completely and run a hot tap until it flows steadily first.
• Cranking the thermostat up to cover a problem. If you need a higher setting to get enough hot water, something is wrong.
• Ignoring a dripping relief valve. It's telling you about pressure or temperature. Don't cap it.

When to call a pro

Call a plumber if the drain valve is clogged with sediment and won't open, the anode rod won't budge, or the relief valve fails its test. HomeGuide puts a professional tune-up at $100 to $500 and a flush at $75 to $250.