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Years of deposits can be removed from water heater

QuestionWe have a gas water heater that is now seven years old, and we've never drained a bucket of water from it as you suggested in your article, "Drain bucketful of water occasionally or install softener. " It must have a tremendous buildup of scale from our hard water because we do not have a water softener either. It works fine but makes loud popping and banging noises after we run the hot water. Is it too late for us to do anything about scale buildup at this point?

AnswerI'm glad you found the article of interest. The rumbling, popping, and banging noises you hear are pockets of water trapped between layers of sediment turning to steam as the water heats. It's like having a zillion mini-volcanoes exploding inside the tank.

I bet the noises are pretty annoying, but there are two more compelling reasons to minimize or eliminate sediment buildup. First, the mineral precipitates form an insulating barrier between the water and the surface of the tank bottom so the tank requires much more expensive energy to heat the water. Second, excess heat on the tank's bottom can lead to premature tank failure.

The quick answer to your question is that an electric water heater may require professional attention, but because you have a gas unit, the odds could be in your favor. To assess your tank's status, begin by draining it. Since the gas burner must be shut off during draining, follow these initial steps (depending upon the water heater's technology). For a standing pilot model, turn the gas thermostat control knob to the pilot position. For an electronic model, turn off the power supply to the heater. Now open the hot side of a household faucet (preferably one nearest the tank) and allow the water to run until it is cool to the touch.

Next turn off the water supply to the tank. With the hot water side of the faucet still open, or by removing the flexible copper tubing connected to the top of the water heater from the cold side using an open-end adjustable wrench, open the drain valve and empty the tank into a suitable drain. Be sure you shut off the main water supply first—unless you enjoy a cold shower. Either method allows air to enter the tank to help it drain properly. Once you remove the flexible tubing, plan to replace it with a new one to guarantee no leakage once the water supply is turned back on.

If your tank doesn't drain properly, the drain valve may be partially or totally blocked by sediment. If this is the case, you'll need to remove the drain valve to physically check its opening as well as the tank's drain valve opening. Before attempting this, create an air lock on the tank by ensuring that no faucets (hot or cold) anywhere in the home are open and by turning off the cold water supply line to the tank.

Next, take a 3/8-inch soft copper pipe roughly 24 inches long and smash one end down with a hammer to form a chisel-like end. Use this chisel end to poke into the sediment to help break it up and to clear the opening. Don't be afraid to penetrate the sediment; the idea is to break it up as much as possible so the water can drain out. Once the opening is cleared, reinstall the drain valve (make sure the valve is in the closed position), turn on the water supply to the tank, and introduce air into the tank by opening the hot water side of a household faucet. Now open the drain valve to drain the tank. If it drains normally, great! However, if it doesn't drain, try the process again. If the tank still doesn't drain, it's possible that the sediment level is above the drain valve level, an indication that the problem has gone too far to permit you to save the tank.

If the tank drains normally, then try a product called Mag-Erad to remove the sediment build-up in your tank. Mag-Erad is a patented food grade chemical concentrate which is non-toxic when used according to the product's directions. You'll need two 1-lb. cans for a 30- to 40-gallon tank, three for 50 to 60 gallons, four for 65 to 75 gallons, and five for 80 to 100 gallons. Designed for use in gas-fired (not electric) water heaters, the product is available for $22.50 per can (including shipping) from Tri-Bros. Chemical Corp. (847-564-2320). I have not personally used the product; however, I've heard through the channels from water heater manufacturers that this is the product to use.

To use Mag-Erad, make sure the tank is completely drained and the drain valve is closed. Again, turn on the hot water side of the faucet closest to the heater to introduce air. Then remove the temperature pressure relief valve (TPR) to vent the tank and provide an opening to insert a funnel. The TPR is located on the side of the tank and should be connected to a discharge tube that points to a floor drain.

For safety, it is recommended that the relief valve be replaced or inspected every three years; however, if you have an older valve, it most likely will never again close properly. Because these units cost very little, it's better to replace it once you have completely cleaned and flushed the tank. The TPR is designed to pop open and provide relief if the tank builds up too much pressure. If this safety valve didn't open, the tank could explode—an excellent reason to replace the valve!

Now follow the manufacturer's complete instructions on the Mag-Erad label, which includes mixing the chemical concentrate with water and pouring the mixture into the relief valve opening using an automotive-type funnel (with a long flexible spout). Then turn on the burner and set the thermostat to 120°F for two hours (consult your owner's manual for the specific settings for your tank) for the actual cleaning cycle.Drawing Courtesy of Tri-Brothers Chemical Corp After two hours, slowly open the cold water supply for 10 to 15 seconds to temper the water. Now turn the gas to the pilot position and drain the tank. Fill the tank roughly halfway and drain it again. Once the tank is drained a second time, remove the drain valve and again use the copper pipe to agitate the sediment. You may have to repeat this procedure a few times to remove all the sediment from the bottom of the tank, something that may be impossible manually because the tank has a concave bottom. Be open to the possibility that a second treatment of Mag-Erad may be necessary. When you're done, don't forget to install the new relief valve and close the drain valve.

Since your tank has not been cleaned in seven years of ownership, expect to spend a half-day on this messy project. My advice is to not wait so long to clean out your next heater; you'll save time and money, prolong the life of your heater, and not have to put up with the annoying popping and banging noises.

To reduce future sediment buildup, perform regular maintenance on the tank by draining a couple of buckets of water every other month. Good luck!

Copyright © 2004, 2006, & 2008 LAF/C.R.S., Inc. All rights reserved.
Question answered by Leon A. Frechette.

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