I flushed my natural gas fired water heater last weekend. No, I wasn’t playing poker, and this was certainly not a gamble. I was just performing annual maintenance to increase the lifespan and sustain energy efficiency of a major home appliance. On the contrary, not flushing a tank annually is a gamble that increases the odds of premature water heater failure. And premature failure odds increase if you have an electric water heater, where sediment will bury and corrode the heating element inside the bottom of the tank. Why be suprised by a water damaged carpet or the replacement cost of a new water heater when a few minutes of preventive maintenance can give you the winning hand?
Flushing is an annual chore relatively easy to do, and doesn’t take too much time while 40 or 50 gals water drains and refills the water heater. Flushing removes calcium, lime, or other mineral sediment build-up on the bottom of the tank that otherwise reduces capacity and insulates the water from the bottom fired gas burner or in-tank electrical element, reducing heating efficiency. Annual maintenance is important is an area such as Salt Lake City, where the water is somewhat alkaline. . . .
Here’s the simple water heater setup. Modify the water heater’s original compression drain valve outlet at the bottom of the tank, replacing it with a 3/4″ IPS straight ball valve with 3/4″ hose threading to allow sediment to pass through without restriction. Then, all you need is to hook up a short length of garden hose from the valve to a nearby floor drain. Of course, this is most easily done at the time a new water heater is installed. Otherwise, drain and then refill the existing tank after conversion following this method.
Now, here’s the flushing procedure, to be done when there is low household demand for hot water. First, and very importantly, turn off the thermostatic gas supply valve or electrical power attached to the water heater so the empty tank or element will not burn. Now, shut off the heater water supply valve at the top of the tank, the pipe marked by blue where it enters the tank. The house water supply shutoff does not need to be turned off. Then open an upstairs sink hot water faucet or two to allow air to replace water draining out of the hot pipes and tank. After a garden hose is connected from the water heater drain outlet to a basement floor drain, open the drain outlet ball valve. Monitor water flow out of the hose. Hot water should begin to flow at least moderately. If water flow is a mere trickle, there may be sediment blocking the ball valve at tank bottom. Turning this valve on and off several times may clear the valve. Also, turn on and off the heater water supply valve several times to add water, breaking up sediment at tank bottom, and jet force sediment through the valve. Again, check the hose end at the drain to be sure water is flowing. The fill supply pipe enters the tank at the top and extends to near the bottom of the tank for this purpose, to in effect swirl and self-clean with makeup water.
After water ceases to flow out of the hose, the water heater is drained, and most sediment should be gone. Now, close the drain ball valve at tank bottom, and open the heater water supply valve at the tank top to fill the water heater. Don’t forget that when the tank is full, air in the tank and hot water pipes is replaced by water which will come out of the sinks hot water faucets, so monitor and shut them off. Finally, turn on the electrical power or gas supply to the water heater. On gas water heaters, the thermostatic valve’s pilot light will need to be relit. Then, turn the valve to on, making sure the burner fires up. Hot water recovery time for most heaters will be about an hour.
Now you’ve got peace of mind in the assurance that you’ve done what you can to prolong the life of your water heater, save an unnecessary and costly repair, and cut down on your electrical or gas utility bill. I’ll bet your next shower will be noticebly hotter. That’s a winning hand.