Maintaining Your Tank Water Heater

Tank water heaters are not quite the simple tub of hot water they appear to be. Inside the shell, there is a rather complex chemistry going on. Ignore it, and your water heater could fail before its time. But following a few simple maintenance tips should keep your cabin flush with hot water for years to come.

Power-drain the tank
Tank water heaters can act as a repository for sediments, so flushing the tank on a regular basis can be instrumental in preventing the rust from corroding the tank from the inside-out.

Here are some instructions you can follow (just keep in mind all drainings are not equal):

1. Make sure you turn off breakers for electric heaters; if you have a gas heater, turn the setting to pilot.
2. Turn off the water heater inlet valve.  
3. Open the drain at the bottom of the tank, open the pressure vent, and then let gravity drain water through a hose to a suitable drainage point. This will take some time, and you might notice the water you drain is mostly free of sediment. That doesn’t necessarily mean there isn’t sediment on the bottom of the tank; the sediment may have settled into a somewhat compacted layer on the tank’s bottom. This layer is often difficult to dislodge with a gravity drain.
4. To get all the sediment out of your tank, you need to add a jolt of fresh water to the mostly empty tank after the aforementioned gravity drain. Leave the vent open, and then open the inlet valve. Cold water will stream into the empty tank, disrupting the sediment layer. 
5. Turn the inlet back off and re-drain, repeating as necessary.

Replace the sacrificial anode as needed
Your tank water heater is basically a metal tub that is filled with water. We all know that metal rusts when exposed to water, so how come we can buy water heaters with 12-year warranties? Shouldn’t they rust out long before then?

The answer is a unique device in your heater called a “sacrificial anode.” This long rod, usually screwed into the top of your water heater (check your manual for exact location) is usually made from aluminum or magnesium. Both of these metals corrode more readily than the steel tank, so the rod “sacrifices” itself, preventing the corrosive elements in the water from rusting out the steel tank.

Sacrificial anodes corrode at different rates, depending on water chemistry, tank temperature and other factors. A good rule of thumb is to replace the anode every two years to maximize tank water life. Magnesium anodes, rather than aluminum, are preferred by most plumbers, since magnesium is more effective and these anodes also tend to be easier to replace.

Rotten egg odors?
Sacrificial anodes are essential to preventing tanks from rusting, but they can have an unfortunate side effect: The breakdown of the anode material can serve as a catalyst for bacterial activity. If your hot water smells of rotten eggs, but your cold water is odor-free, it’s a good bet that your water tank is inhabited by harmless, but stinky, sulfate-reducing bacteria. For many cabins, extended periods of heater downtime can increase the likelihood of having smelly hot water (bacteria need temps less than about 140°F to get going, and cabin outages can create prime breeding periods).

One of the best ways to get rid of the bacteria is to add a pint of hydrogen peroxide for every 40 gallons of hot water.   This may take a bit of creative plumbing; a common approach is to install a valved T on the heater’s inlet pipe to add in the peroxide. Most tanks are odor free within an hour of adding the peroxide.

TIP: Water that is soft and naturally corrosive will react more strenuously with sacrificial anodes, increasing the likelihood of stinky water and premature tank failure. For corrosive water, consider replacing the sacrifical anode with a powered anode. It’s more expensive, but doesn’t corrode, and IT starves bacteria SO IT WON’T cause stinkiness.