Short answerFlush a tank water heater once a year to clear sediment, and check the sacrificial anode rod every 3 to 5 years, replacing it when it is mostly bare wire. In Southeast Michigan's hard water, those two steps are the difference between a tank that lasts 8 years and one that lasts 15. Test the temperature and pressure relief valve at the same time.
Two jobs that most tanks never get
The average 40- or 50-gallon atmospheric gas water heater in a Washtenaw or Wayne County basement is installed, forgotten, and replaced when it leaks. That is a shame, because the two maintenance tasks that extend tank life are simple, and the tank itself is designed around them. Sediment flushing keeps the burner from cooking a layer of mineral at the bottom of the tank, and the anode rod, a long rod of magnesium or aluminum screwed into the top, exists to corrode so the steel tank does not. When the rod is gone, the tank starts rusting from the inside, and the leak follows within a few years.
Both jobs are more important here than in many places because of the water. Municipal water in Ypsilanti, Ann Arbor and the Detroit-system suburbs runs moderately hard, and the well water in Augusta, York, Lodi, Salem and the rural townships is often very hard, with iron on top of the calcium. Hard water means more sediment and a faster-consumed anode.
Why sediment matters
Water heated in the tank drops calcium carbonate and other minerals out of solution, and they settle to the bottom, directly above the burner on a gas unit. A half inch of sediment acts as insulation between the flame and the water. The burner runs longer to reach temperature, the tank bottom overheats, and the steel and glass lining fatigue. You can hear it: a popping, rumbling or kettling sound after the burner lights is water boiling under the sediment layer and bursting through it.
Sediment also:
- Reduces usable hot water, because it occupies tank volume and holds cold water near the bottom.
- Clogs the drain valve so badly that by year ten it will not drain at all.
- Fouls the burner and the flame arrestor screen on newer sealed-combustion tanks, which can cause the pilot to go out, the symptom covered in water heater pilot light won't stay lit.
- On electric tanks, buries the lower element and burns it out.
How to flush the tank
This is a reasonable homeowner job on a tank that has been flushed before. On a 12-year-old tank that has never been drained, the drain valve is likely plastic, brittle and packed with sediment, and opening it can leave you with a valve that will not close. In that case, let us do it, because we bring a replacement valve.
- Turn the gas control to "Pilot" or "Vacation," or shut the breaker on an electric tank. Never run the burner or elements with the tank partly empty.
- Shut the cold water inlet valve on top of the tank.
- Connect a garden hose to the drain valve at the bottom and run it to a floor drain, a sump pit, or outside. The water will be hot; let the tank cool for an hour if you want to be safe.
- Open a hot water faucet upstairs to let air into the system.
- Open the drain valve. The first water out will be rusty or cloudy. Let it run until clear.
- With the drain still open, briefly open the cold inlet in short bursts to stir up and push out the remaining sediment. Repeat until the water runs clean.
- Close the drain, remove the hose, open the cold inlet, and wait until water runs steadily from the open upstairs faucet before relighting the pilot or restoring power.
Once a year is right for city water. On a well in the rural townships, every six months is not excessive.
The anode rod
Pull the anode rod every 3 to 5 years. On most tanks it sits under a hex head on the top of the tank, sometimes under a plastic cap, occasionally combined with the hot water outlet nipple. A new magnesium rod is about 3/4 inch thick and 3 to 4 feet long. A spent one is a thin steel core wire with chunks of crumbling material or nothing at all hanging from it.
Replace it when more than about 6 inches of bare wire is showing, or when it is pitted down to half its original thickness. Options:
- Magnesium: the standard, protects best, consumed fastest in hard water.
- Aluminum/zinc: lasts longer in hard water and reduces the rotten-egg sulfur smell that magnesium rods can cause in well water with certain bacteria.
- Segmented (flexible) rods: for tanks installed under a low ceiling or ductwork where a 44-inch rod cannot be lifted straight out. Common in Michigan basements with 6-foot-6 clearance.
- Powered anodes: an electrically driven titanium rod that is never consumed. Worthwhile on a tank you expect to keep a long time, or in a well-water house fighting sulfur odor.
The hex head is often seized after years of heat cycling. It takes a 1-1/16 inch socket, a breaker bar, and someone holding the tank so it does not twist on its connections. If it will not move, stop before you crack a fitting.
The relief valve and the rest of the checkup
While you are down there:
- Lift the T&P valve lever on the side or top of the tank for a second. Water should rush out of the discharge pipe and stop when you release it. If it dribbles afterward or did not flow, the valve needs replacing. It is the device that keeps a tank from becoming a pressure vessel failure, so this matters.
- Look at the venting on an atmospheric tank: the draft hood should sit square on the tank, the metal flue should slope up to the chimney, and there should be no rust flakes or soot on top of the tank. Hold a match near the draft hood edge with the burner running; the flame should pull in toward the hood, not blow out.
- Check for corrosion at the water connections on top and around the base, and for a damp spot under the tank. A tank that is sweating or seeping at the base is near the end, and water heater lifespan and replacement signs covers what that means.
- Confirm the temperature setting. 120°F is the usual recommendation for scald safety and efficiency.
- Look at the expansion tank if you have one, a small blue or white tank on the cold line. Tap it; the top half should sound hollow. If it is waterlogged, it is no longer doing its job.
Any smell of gas near the tank means leave the house, then call DTE at 800-947-5000 and 911 from outside.
When it is time to call instead
A tank older than about 10 years that has never been serviced, a drain valve that will not open or close, an anode hex that will not break loose, a T&P valve that fails the test, or a tank in a tight spot with no clearance above it. Those are the jobs we do on a water heater repair visit, and the dispatch fee covers the inspection. If the tank is near the end anyway, we will say so plainly, and the replacement conversation starts with water heater replacement cost in Michigan.