A tank water heater needs a few simple maintenance tasks to keep working well. The U.S. Department of Energy says periodic maintenance can significantly extend your water heater's life and minimize loss of efficiency. This guide covers the three main tasks: flushing sediment, checking the anode rod, and testing the temperature and pressure relief valve. Always follow your owner's manual first, because steps vary by model.
Safety first: read this before you start
Water heaters combine scalding water, high pressure, and either natural gas or high-voltage electricity. Follow these rules:
- Gas smell: If you smell gas, stop. Do not touch light switches, use a phone, or do anything that could make a spark inside the house. Leave on foot, then call 911 and CenterPoint Energy's leak line from a safe distance. Do not try to shut off the meter or fix a leak yourself. This follows CenterPoint Energy's gas leak safety instructions.
- Scald risk: Water in the tank and from the drain valve can cause serious burns. The U.S. Consumer Product Safety Commission reports that 140°F water can cause third-degree burns in six seconds and recommends setting water heaters to 120°F. See the CPSC tap water scald safety alert. Wear gloves and closed-toe shoes, and let the water cool for a few hours before draining if you can.
- Electric units: Turn off the breaker before you drain. Do not turn the power back on until the tank is completely full. Heating elements that run without water around them can burn out.
- Gas units: Set the gas control to the setting your manual specifies (usually "Off" or "Pilot") before draining. If you are not comfortable with the gas control or relighting a pilot, call a professional.
- Relief valve discharge: Never stand in front of the relief valve discharge pipe when testing it, and never cap, plug or remove that pipe.
Why sediment builds up
Minerals in your water settle to the bottom of the tank over time. Sediment takes up space, separates the water from the gas burner, and makes the unit work harder. Signs include popping or rumbling sounds, rusty or cloudy hot water, and running out of hot water faster than usual. Homes with hard water build up sediment faster.
How to flush a tank water heater
Many manufacturers recommend flushing once a year, and more often with hard water. Check your owner's manual for your model's schedule. The general steps are:
- Turn off the power at the breaker (electric) or set the gas control to Off or Pilot (gas).
- Close the cold water supply valve at the top of the tank.
- Connect a garden hose to the drain valve near the bottom of the tank. Run the other end to a floor drain or outside, at a level lower than the valve. Make sure the hose end will not spray hot water on anyone.
- Open a hot water faucet somewhere in the house to let air into the system.
- Open the drain valve slowly. Let the tank drain until the water runs clear.
- With the drain still open, briefly open the cold water supply to stir up and rinse out remaining sediment. Repeat until the water runs clear.
- Close the drain valve and remove the hose.
- Open the cold water supply and leave the hot water faucet open until water flows steadily with no air sputtering. This means the tank is full.
- Close the faucet. Restore power or return the gas control to its normal setting following your manual.
- Check the drain valve for drips over the next day.
Stop and call a professional if the drain valve will not open, will not close fully, or leaks after you close it. Old plastic drain valves can break when opened. Do not force them.
Checking the anode rod
The anode rod is a metal rod inside the tank. It corrodes on purpose so the steel tank does not. Once it is used up, the tank itself starts to rust. The Department of Energy recommends inspecting the anode rod every three to four years. See the Department of Energy guide to storage water heaters.
Replace the anode rod if you see:
- Steel core wire showing through along much of its length
- Heavy pitting or a rod worn much thinner than its original size
- A thick coating of calcium deposits
For most homeowners, this is a task to leave to a technician. The rod often sits under a cap on top of the tank and can be hard to loosen. Replacing it requires shutting off water and draining some of the tank, and many basements do not have the overhead clearance for a full-length rod. Forcing a stuck rod can damage the tank fittings.
Testing the temperature and pressure relief valve
The temperature and pressure (T&P) relief valve opens if the tank gets too hot or the pressure gets too high. It is the most important safety part on the water heater. Check your manual for the testing schedule. To test it:
- Make sure the discharge pipe runs down toward the floor or a drain and nothing is in its path.
- Stand to the side. Lift the valve lever briefly. Hot water should flow out of the discharge pipe.
- Let the lever snap back and confirm the flow stops.
If no water comes out, turn off the water heater and call a professional. If the valve keeps dripping after the test, or if water discharges from the pipe during normal use, call a professional right away. A discharging valve can mean the tank is overheating or over-pressured, or the valve is failing. Never try to repair, adjust or plug the valve.
When to call a professional
Call for service if you smell gas (after you leave the house and call 911 and the gas utility), if the relief valve leaks or does not open, if the drain valve is stuck or leaking, if the anode rod needs to be checked or replaced, or if you see water leaking from the tank. A technician can also handle the full maintenance visit for you. Learn more about water heater service and repair at Krinkie's.
Common questions
How often should I flush my water heater?
Many manufacturers recommend flushing once a year, and more often if you have hard water. Follow the schedule in your owner's manual.
How often should the anode rod be checked?
The U.S. Department of Energy recommends inspecting the anode rod every three to four years. Replace it when the steel core is exposed or the rod is heavily worn.
What temperature should my water heater be set to?
The U.S. Consumer Product Safety Commission recommends 120°F to reduce the risk of scald burns.