Electric water heaters are common and useful appliances in many homes. Due to the pressure involved with heated water, they can be quite dangerous, so make sure you hire a licensed plumber for installation and maintenance. The electric water heater has many external features, but let's talk about a few of the internal parts.
Underneath the exterior is a wrap of insulation to keep heat trapped for energy efficiency. Underneath that is likely either a glass or porcelain lining which seals water inside the tank. Cold water flows into the heater through a dip tube, which forces cold water to the bottom of the tank. Hot water exits directly from the top of the tank. The dip tube allows for more consistent hot water, because cold water enters low, is heated up, then exits as hot water. Without the dip tube, cold water may just get sucked directly through a loop while hot water stays at the other end of the tank. It also allows water to be used “first in, first out” instead of constantly mixing hot and cold for a medium temperature on the hot line.
Two heating elements are inserted into the tank, which act like elements in an electric oven to heat water. One element at the bottom does most of the work – as cold water first comes in at the bottom of the tank through the dip tube. The upper element is supplemental and maintains water temperature throughout the day. Due to physics and the fact that water is rarely pure distilled H2O (nor should it be – humans need minerals and other elements mixed in), buildup /could/ occur on these elements that lead to a burnt out element. And it does build up there. But not as fast as it could, thanks to our next component, the anode rod.
An anode rod is a sacrificial element. This means its entire purpose in your water heater is to attract sediment and corrosive elements, before they can damage the tank itself. Through electrolysis, the anode rod attracts ions in the water which would otherwise attack the water heater tank lining and lead to corrosion, rust, and leaks. The lifespan of your anode rod depends on the type of water you have. Because it is made from a material that is ‘weaker’ than the tank, it accepts the brunt of damage for your tank overall.
Finally, we have a thermostat. This gauges the temperature of water in the tank, and controls power to the heating elements for consistent water temperature. While there is some debate about the temperature of water INSIDE the water heater, it is largely agreed that water at fixtures should not exceed 120f for most purposes to prevent scalding. Higher temperatures are believed to prevent growth of legionella, which leads to legionnaires disease. For the best of both worlds, a tempering valve can allow hotter water inside the tank while mixing water temperature to safer levels as it leaves. There are more components to the water heater, but these are the most important and misunderstood portions inside the tank. Each one serves a vital, and underappreciated, purpose.
Too Long, Didn't Read Version: Your water heater is a wonderful piece of equipment that is simple, complex, and underappreciated. Simple routine care may prolong the life expectancy and protect your family.
-Marshall Tramp, CPI, RMP
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