Friday 22 March 2019
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How and why you should flush your water heater

Flushing isn’t just for toilets. Depending on your water source, there’s likely to be some sediment inside your water tank. It could be chipped off debris from the tank, or contaminants in the water. If your water is hard, there are lots of benign mineral deposits. They’re safe for drinking, but when they accumulate, they can interfere with your boiler.

Even if your water source is soft, there may be chlorine and other disinfectants that can solidify and collect at the sides and bottom of the heater. When the water boils, this residue circulates within the water, blocking pipes and altering the boiling temperature. This means you use more energy to get the same amount of heat. Sometimes, the water won’t boil at all.

When your heater stops working, your first step is to call a plumber, or to visit a hardware store and buy a replacement. While these are options, you can sometimes resolve the problem by flushing your water heater. Drain all the water, rinse it out, and refill it with fresh water. If you do this once a year, your boiler will last a lot longer.

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Identifying sediment

Listen to your water heater, literally. Don’t press your ear against it – you’re likely to get a bad scalding. Instead, get the house as quiet as possible, then turn on the heater and listen. If you hear popping or rumbling sounds, it probably means you have a nasty sediment problem. The damage will depend on the kind of boiler that you’re using.

If your water heater is electric, it probably has a heating element at the bottom of the tank. These are more effective because as the water hot, it gets lighter and flows to the top of the tank, while colder water sinks to the bottom and gets heated in turn. Unfortunately, when sediment builds up, it settles on those hot filaments at the bottom of the tank.

When you turn on the heater, the sediment gets bounced around on the heating elements, or sometimes prevents them from heating up effectively. Steam from the boiling water struggles to get through the layers of residue. That’s what causes the popping noise. Gas heaters respond in a slightly different way.

Since the flame is outside the heating tank, the sediment itself gets heated up and reaches a higher temperature than the water. Since these hot spots are at the bottom of the tank, they can pierce it and cause leaks or spoil the heater altogether. Most heaters have a drain valve for flushing. However, once you open it, the drain can get clogged by sediment.

Unclogging a blocked opening

If the opening is blocked, you can’t drain the heating tank completely, and even if you do, it may be unable to close. This can lead to a persistent leak in your water heater. You can remove the sediment by constructing a vacuum adapter. It’s easy to make using parts from your local hardware store and any YouTube tutorial. You might also need a new drain valve.

Most heaters have a pressure valve to prevent the boiler from exploding when the water gets too hot. Remove the pressure valve and insert your vacuum adapter. Place a vacuum hose on the other side of the adapter. The suction will pull out any clogged sediment, and it’ll draw out the water as well. The ‘vacuum hose’ could simply be a garden hose.

Another option is to use gravity rather than suction. Turn off your power source then open your hot water tap at full pressure. Let the water run for about ten minutes. This reduces the heat inside the tank by drawing in cold water from the mains. Now use the drain valve to let out the rest of the water in the heater. You can put a colander at the outlet, to trap sediment.

Open both the tap and the drain at the same time, so that all the water in the heater flows out. If the drain gets clogged, close the tap and repeat the process so that more water flows into the tank to dislodge the sediment. If the clog is completely plugged, take out the drain valve and insert your home-made drain adapter. Use that to let the water out.

You may need a few cycles of flushing before the sediment is all extracted. You’ll know it’s gone when the water runs clear. At this point, the old drain will probably be too full of residue to close properly. Once the heater is completely empty and free of sediment, install a new drain valve. You can do it yourself, or you can call a plumber to help.

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