"How often should I drain my water heater?"
Column #810 08/28/10
On The Level
Q. We bought a new townhouse a few years ago and we are trying to do all the right things to maintain it. This is our first home and we are new at some tasks that have to be done. I have friends at work who say the water heater should be drained and cleaned once a year. I havenít done that yet and I wanted to check before I did anything to be sure Iím doing it right. We havenít had any trouble with the water heater. Any suggestions?
A. I have to put in a good word for our local municipal water supply and suggest that you really donít need an annual water heater draining program like one would on well water. And if you live in a townhouse you are on City or County water. Thatís how they build them around here-- on municipal water and sewer services. Ask your friends at work if they are on well water.
One drains a water heater ostensibly in hopes of draining out any sediment that may have settled to the bottom of the tank. Since we canít see into the water heater tank some think that a given interval for draining tanks makes sense and on some water supplies that is true.
I tell people who ask me how often they should drain their water heaters to keep them clean to perform a simple task first. Lift the lid of the rear of a toilet and see what sort of sediment is on the bottom of that tank.
If there is little to none then I can conclude thatís what the bottom of the water heater will look like. After all, the basic function of the two tanks is the same. Both systems maintain a stand-by quantity of water in anticipation of use. The only difference is one is for hot water and the other for a flush. Both reservoirs will sit for hours on end without being used so if there is anything suspended in the water it is likely to settle to the bottom of the tank. City and County water is very clean and draining intervals of such water heaters can be timed in decades rather than years. Sometimes the public works guys will work on or repair a water main and the water might not be a hundred percent clear for a short while but that doesnít amount to anything to worry about.
Water heaters of any type do not fare so well on well water. Well water traditionally shortens water heater life and draining them from time to time is a good idea for hygiene but doing that wonít extend their life.
Frequently as gas water heaters age they will develop a mineral scale inside of the tank and when the burners come on and heat up the tank homeowners will hear a popping noise coming from the tank. Those are tiny bubbles of steam forming between the scale and the steel tank that instantly cool once they hit the water beyond the thin scale.
While draining a water heater for cleanliness I would leave the supply water on to give the drain spigot some pressure. You donít ever want to drain any water heater down removing all its water while leaving the unit on. Youíll ruin it. Thatís a common mistake when reopening a house thatís been winterized with all reservoir tanks drained down. The power gets turned back on first to get the lights back on and if the water heater (electric) breaker is on the elements will destroy themselves before water can get to them. It doesnít take long and itís the type of mistake that someone only makes once.
For those on well water I have to put a plug in for UVC sanitizer lights on the main supply coming in from the well. They have been out for many years and they will kill 99.9% of the bacteria that passes them on the way in the house. Ask any well professional and they will tell you that even after a well has been ďshockedĒ and sanitized with bleach, it doesnít take long for the bacteria to come back. And water conditioning doesnít sanitize.
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