Is your water heater making odd noises? Does it seem you run out of hot water sooner than you used to? Maybe it’s time to flush the sediment out of your water heater.
I often see it stated that a build up of sediment in the bottom of your gas water heater leads to lower efficiency. This would at first seem to make sense. The flames are heating the bottom of the tank, and if there is a thick layer of sediment then maybe it would be harder to heat the water in the tank and lead to lower efficiency.
However, I read somewhere that a buildup of sediment does not impact the efficiency of the water heater. I believe it was a study done by Battelle Labs, but I don’t remember for sure. The study found that there was no significant reduction in water heater efficiency with a buildup of sediment.
If you think about it carefully it makes perfect sense. The flames still transfer their heat to the metal bottom of the tank, which is wetted on the inside of the tank, and thus the heat is transferred into the tank at the same efficiency. The difference is some of the material being heated is sediment, which will impart that heat to the water it’s in.
Hence there is no real loss of efficiency. There may be less water available to use since sediment does displace volume, but with no impact on water heater efficiency. However, if you don’t live in an area with hard water you probably won’t accumulate enough sediment to make a noticeable difference in the capacity of your hot water heater.
There are noises that gas water heaters can produce as a result of mineral deposits or sediment buildup, like gurgling, popping and banging noises. This is caused by the heat from the burner causing some of the water sitting against the bottom of the tank to turn into steam bubbles. As the bubbles work their way up through the sediment they can produce all sorts of odd noises.
The solution is to flush the sediment out of the heater.
With electric water heaters the elements can become incrusted with mineral deposits which can flake off and contribute to sediment buildup. With electric water heaters the buildup of minerals on the heating elements does not cause a decrease in efficiency. The heat generated by the heating elements still ends up inside the tank, so no decrease in efficiency. The buildup can however lead to higher temperatures in the elements and cause premature failure of the heating elements.
Tankless water heaters can also suffer from scale buildup in the heat exchanger. Obviously sediment buildup is not a problem for tankless water heaters, but scale build is. The buildup of scale on the heat exchanger can lead to reduced water flow causing the heat exchanger to over heat which will lead to problems.
In fact, if you read the owner’s manuals you will find that most tankless water heater manufactures specify the maximum hardness of water that you can use the unit with and still have a valid warranty. Too hard and the warranty is void. In those cases they recommend using a water softener.
Most also recommend that you de-scale your water heater periodically to prevent the buildup of scale. I think they have you run vinegar through it or something. I can’t exactly remember and I am too lazy to go look. From reading the owners manual it doesn’t sound like anything I would want to spend my Saturday afternoon doing.
Another area where sediment and scale are a problem is with hot water recirc systems. Hot water recirc or recirculating systems pump hot water for long periods of time and thus suffer from scale buildup. This is probably the primary reason for recirc pump failures.
Hot water demand systems such as the Chilipepper, Metlund D’mand System, and the Armstrong system, do not suffer from scale because they don’t really circulate hot water. Since the pumps shut off as the hot water arrives, they never really pump water that is actually hot, and they never run for long periods of time with hot water in them. Hot water is the culprit to blame for scale buildup, and so demand systems simply don’t have a scale buildup problem.
If you need to flush the sediment from your water heater: Flushing Your Water Heater
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