How To Handle Corrosion Problem Spots in a Water Heater

7 Common Places to Find Corrosion

Corrosion can cripple the life of your water heater no matter if you have a tank-type, commercial or solar water heater system. Learn where the 7 trouble spots for water heaters are and how to protect your water heater from corrosive elements.

  1. Electric Elements. Galvanic corrosion occurs when one metal corrodes because it is in contact with a second metal. This is the type of corrosion most often found in electrical water heaters. Electrical elements (the heating plates inside the tank) are made of steel with a copper sheath. When both the outer copper and the inner steel base become wet, electrolysis and corrosion result. If the corrosion continues, eventually the element will fail to heat the water in the tank. If you replace the electrical element and corrosion occurs within a year, it is the anode rod which will need to be replaced.

    You can prevent galvanic corrosion by installing galvanized unions using plastic nipples on top of the tank. Plastic plumbing is not subject to galvanic corrosion. PB and CPVC can adapt to most metal pipes.

  2. Anodes. Anode rods are essential to the long-term health of your water heater. The anode rod prevents corrosion of the rest of the water heater by sacrificing the metal within the rod. In essence, if working properly, the anode rod will corrode instead of the water heater. Sometimes, anode rods can become covered by a very hard layer of calcium carbonate (see Anode Rods). This will prevent the anode rod from doing its job and the water heater itself will start to corrode. The only way to tell if an anode rod is covered in calcium carbonate is to remove it and attempt to bend it. If it bends easily then the anode rod is no longer serviceable.
  3. Combustion Chambers. The combustion chambers in gas water heaters are another trouble spot for corrosion. They should be checked regularly for corrosion and rust. To do this, first set the gas control to PILOT. Remove the hatch cover and then the draft diverter (the hood on top of the tank that gathers exhaust gases and diverts them to the vent) and the baffle (this will be inside the flue pipe inside the tank). You will need to use a flashlight to check inside the flue pipe for any water damage. If there is any rust or corrosion call a plumber as soon as possible.

    In commercial water heaters, you will need to drain the tank and check the interior for rusting. If it is present, call the manufacturer for maintenance.

  4. Vent Pipes. Another problem area in gas water heaters are the vent pipes. These pipes above the water heater vent the combustible gases from the water heater to the outside. The venting system has numerous plumbing codes with specific instructions for professionals, so do not attempt to do any work on the venting system yourself. Simply check the pipes for any rusted holes. If you find any, call a plumber immediately. By-product gases as well as any unused natural gas will escape from these holes and linger in the area directly surrounding your water heater.
  5. Corrosion Caused by Softened Water. Water softening removes or chemically reacts with hard minerals in order render them inert. The most common water softening agent is salt, which can often be more corrosive and consume anode rods faster than the hardening minerals found in hard water. If you have softened water, check the anode rods a minimum of every two years.
  6. Corrosion Resistant Materials to the Rescue. Many water heaters now use more corrosion resistant metals or other materials for the tank lining instead of steel or glass. Some of these corrosion resistant materials include copper, stainless steel plastic or cement. If you’re concerned with corrosion problems of the tank itself, consider installing a tank made out of some of these corrosion resistant materials.
  7. Solar Water Heater Systems. Today, solar water heating systems have eliminated most of the corrosion problems they faced in earlier versions. One problem area that should be checked however is the heat exchanger. Inside these machines is an oily heat exchange fluid which does not drain in cold weather (although it does not freeze either). In this situation, corrosion can occur; solar water heaters should be monitored in cold seasons.


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