Homeowner Helpers: Is your hot water tank full of gunk?

Homeowner HelpersIf you’re like most people, the water in your home is heated inside a hot water tank that looks nice on the outside but is probably disgusting on the inside. Unless your water heater is new, the bright, white exterior probably encloses a steel tank that’s black, ugly and filled with sediment.

Even super-diligent people I know don’t seem to realize where their water travels on its way to the shower. There are two reasons everyone should.

Even the safest tap water contains minerals that accumulate in the bottom of every hot water tank. Constant temperature fluctuations in the tank and long periods of stagnation create the perfect conditions for minerals and impurities to precipitate out of the water and settle onto the bottom of the tank.


Annual water heater flushing is the first and most important maintenance step to getting rid of mineral deposits.

hot water tank mineral deposits

This is the kind of mineral sediment that gets flushed out of the bottom of tank-style water heaters. Appearance will vary depending on the chemistry of your water.


At the bottom of every tank-style hot water heater there’s a drain valve, and this is the only place where crud can leave the tank.

The process of flushing is simple:

  • Shut off the electricity or gas supply to the water heater.
  • Shut off the water valve supplying the tank.
  • Connect a garden hose to the bottom valve.
  • Place the end of the hose in the closest drain.
  • Then turn on the water valve supplying the tank.

As new water is added to the tank from above, it leaves through the drain valve at the bottom, carrying a surprising amount of ugly stuff with it. This is the basic flushing process, and it should happen once a year.


If your water heater has been neglected for years, expect a lot of gunk to come out. It’s not unusual for five to 10 lbs. of minerals to flush out from high mileage heaters in hard water areas.

To conserve energy and make the flushing process safer, I always shut the electricity off to our heater a day or so before flushing, allowing the hot water to be used up, rather than dumping it down the drain.

The cost factor

Water heater sediment is ugly, but appearance isn’t the only reason flushing makes sense. Reducing energy costs and boosting the hot water capacity of your tank is the most important reason for flushing.


The more minerals in the bottom of your tank, the less effective your water heater will be. Flushing is an effective way to remove most of the sediment, but it won’t get it all. So, if you’d like to do better, consider the vinegar tea kettle treatment.

Vinegar is a safe, effective and inexpensive acid that dissolves waterborne mineral deposits quickly and easily. It’s very effective for cleaning kettles, and it works just as well on water heaters, too.

Making a sacrifice

The only hitch is getting the vinegar into the tank after the initial flushing, and this involves becoming familiar with something called a sacrificial anode rod.


hot water tank anode Steve Maxwell

The partially used sacrificial anode, right, used to look like the fresh one, left. The anode corrodes slowly so that your water heater tank doesn’t.

Corrosion is an ever-present danger for the steel tank of your water heater, but corrosion is a funny thing. It always attacks the easiest metal to corrode first, leaving the more inert metals alone until there’s nothing else around.


That’s why every water heater has a replaceable rod inside the tank. This is called a sacrificial anode, and it usually threads in through the top. As long as enough corrodible metal remains on the rod, your tank is safe from rusting.

Part of water heater diligence involves removing the anode to see how it’s doing, replacing it after it’s about half gone. A 1 1/16-inch socket is standard for removing all water heater anodes, though the job often requires a lot of muscle.

hot water tank Steve MaxwellShut off the water to the tank, then let all the pressure drain out the open drain valve. Use a piece of pipe or 2×2 lumber placed between the outgoing water pipes from the tank to stop the tank from turning as you wrench out the old anode.


Most brands of tank-style water heaters are very similar, and I needed to pry off a white plastic collar around the anode hex head on the top of the heater to get my socket wrench down onto mine. You’ll probably need to do the same.

Anode removal is a little beyond normal DIY work, but whether you do the job yourself or hire a pro, anode inspection and replacement is still a necessary part of optimizing water heater life. Whenever you declare it to be “anode day” at your house, it’s also a good time to have two or three gallons of vinegar on hand to dump into the tank down the anode hole for deep cleaning results.

Vinegar rinse

Before you do any of this anode stuff, flush the system as best you can, as I explained before. Next, shut off the drain valve, but leave the hose hooked up for now.


After the anode comes out, dump vinegar into the tank with a funnel in the hole left by the absent anode, then leave it there for three or four hours. As long as the remaining sediments that didn’t flush out are soluble minerals (and they almost always are), the vinegar will dissolve them. Of course, you won’t have hot water while all this is happening, so pick your time of day.

Finish up by flushing the vinegar out as you did before. Remove the garden hose and close the valve, replace the anode rod (either the old one if it’s still good, or a new one), and turn the water to the tank back on.

Open hot water taps somewhere in the house until air stops coming out and water flows freely. When you’re sure the tank is completely filled with water (and only then), turn the electricity or gas back on.


You’re now very much in the minority. You’ve got a squeaky-clean water heater that’ll work as efficiently as it’s designed to for the next year or so.

Got a maintenance task you’re not sure how to do?
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About the Author

Steve Maxwell

Steve Maxwell

Steve Maxwell has been helping Canadians with home improvement, gardening and hands-on living since 1988. Visit for videos, stories and inspiration.



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