How to test the T&P valve and check the anode rod
To test a T&P valve, A. O. Smith's manual says to operate it by hand at least once a year, with no one near the discharge pipe. Water should flow, then stop when the lever closes. Inspect the anode rod within three years of installation, then yearly. Have a plumber replace a valve that won't reset.
What a water heater relief valve test and anode check do
These are two separate safety and lifespan checks on a tank water heater. The temperature and pressure (T&P) relief valve is the tank's emergency release. If the water ever got too hot or the pressure too high, this valve would let it out. The risk is a valve that has seized from years of sitting still, and you only find that out by moving it.
The anode rod is a metal rod inside the tank that wears away so the steel tank doesn't. When it's used up, corrosion moves on to the tank. Softened water uses it up faster.
Intervals come from your heater's manual, so check that first. One A. O. Smith residential manual says to operate the valve at least once a year. It says to inspect the anode no later than three years after installation and yearly after that, or yearly from the start if your water is artificially softened. Other brands may differ, and some manuals call for a qualified technician to do the anode inspection.
How to test a T&P valve, step by step
- Read the manual for your model
Look up the maker's interval and warnings. The model number is on the tank's label.
- Clear the area
Make sure no one is near the outlet of the discharge pipe, and that hot water won't damage anything. It may be scalding.
- Place a bucket
Set a heat-safe bucket under the pipe end, and wear closed shoes. Keep your hands away from the outlet.
- Lift the lever
Raise it for a few seconds, and let it snap back into place. Water should flow out, then stop.
- Watch for a few minutes
Check the pipe for drips after the test. A valve that hasn't moved in years may not reseat cleanly.
- Date the anode check
Work out the heater's age from its serial number, and schedule an inspection by the three-year mark.
- Book the plumber
Ask for an anode inspection and a written note of what they find, then add it to your home records.
T&P valve test results and when an anode is used up
| What you see | What it means | What to do |
|---|---|---|
| Water flows when lifted, stops when released | The valve works | Note the date and test again next year |
| Nothing comes out | The valve may be stuck | Stop and have a plumber replace it |
| Keeps dripping after you release it | The valve didn't fully reset | Try it once more. If it still runs, it needs replacing |
| Drips now and then on its own | Often thermal expansion from a check valve on the water line | Ask your water supplier or a plumber. Don't plug it |
| Anode: most of the rod under 3/8 inch thick | Used up, per the manual | Replace it |
| Anode: about a third or more of the core wire showing | Used up, per the manual | Replace it |
| Anode: still thick and mostly intact | Fine for now | Recheck in a year |
T&P valve dripping or stuck? What to do next
A relief valve that won't open or won't close needs replacing, and the tank has to be drained to do it. The A. O. Smith manual says to close the cold water inlet, drain the heater and fit a new valve. On any heater, this is a good job for a licensed plumber, and permit rules vary by area.
Never plug, cap or remove a relief valve to stop a drip. The manual warns against it directly, because the valve is what releases dangerous pressure.
Anode work means turning off the gas or power, shutting off the water and draining about 5 gallons before the rod comes out. The new rod's threads get sealed with Teflon tape or approved pipe sealant, then the tank is refilled and checked for leaks. Don't leave the rod out to solve a smell problem, because the manual says that voids the warranty. A special rod may help with odor.
If you smell gas, leave the area and call your gas company. Don't work on gas parts yourself.
What homeowners say about how to test a T&P valve
Once a year, fill a tub with only hot water and look at the color. One owner saw rust-colored water and a plumber found a small tank leak before it burst. Do this check yearly once the heater is about 10 years old. Another owner's anode had dissolved and the tank leaked right after its 6-year warranty ran out. (Reddit)
The anode rod nut is often seized. Owners report needing a long breaker bar and help, and some gave up and had a plumber do it. (Hacker News)
Where owners disagree: DIY pros say explosions need several safety failures at once and call many warnings plumber scare stories. Still, test the T&P valve and keep the temperature near 120°F. (DIY Stack Exchange)
How often to check an anode rod, and other questions
Why does my T&P valve drip a little?
If it drips periodically, thermal expansion is a common cause, often linked to a check valve in the water line or at the meter. A manual suggests asking your water supplier. Don't plug it.
How often should I check the anode rod?
One A. O. Smith manual says no later than three years after installation, then annually. With artificially softened water, it says to check every year.
Can testing the T&P valve cause a leak?
Sometimes. An old valve may not fully reset after it's lifted. That's still worth learning now, because a valve that won't open can't protect the tank.
Sources: manualsdir.com, This Old House
General guidance for U.S. homes, not professional advice. For gas, electrical and structural work, call a licensed pro.