How To Prevent Rusting in a Water Heater

Upgrade To Plastic-Lined Nipples

Problems with rusting

What Are Plastic-Lined Nipples And Why Do I Need Them?

Pipe nipples are small fittings that connect two pipes together. Many pipes and pipe nipples are made out of brass or copper because these metals are “noble” metals. This means that brass and copper do not chemically react with oxygen—the cause of corrosion or rusting—as much as other metals do (such as steel). The hot and cold water lines on top of the water heater are usually made of brass or copper. Unfortunately, most water heater tank linings and pipes are made out of steel. If these different metals touch each other, the brass or copper will actually promote rusting on the steel tank while the brass or copper remain rust free.

To solve this problem, dielectric unions and plastic-lined pipe nipples were invented. If your water heater system has only copper or brass pipe nipples directly touching the steel tank, replace them with plastic-lined nipples immediately. Don’t panic though. There shouldn’t be serious corrosive damage to your water heater unless your water heater is brand new or only a few months old.


  1. Attach a plastic-lined pipe nipple to both the hot and cold water lines where the pipes protrude from the wall.
  2. Attach another set of plastic-lined nipples to the water heater itself where the hot and cold water lines connect to the steel tank.
  3. Next install copper flex-connectors to connect the hot water line from the wall to the water heater tank. Do the same for the cold water line. Set up heat traps here as well to increase your water heater’s heating efficiency (see Shrink Your Power Bills). Be sure to attach adapters to the copper plumbing
  4. If you have an affinity for plumbing you can also install gate valves on your hot and cold lines while you are installing the plastic-lined nipples. Use brass gate valves and install them into the plastic-lined nipples connected to the water heater tank. Then connect the hot and cold water lines to the gate valves. This will give you control over the water lines at the water heater connection itself. You can install heat traps here as well where the plastic-lined nipples are installed. Hire a professional plumber to do this.
  5. There are several other places you may need to install a plastic-lined nipple.
    • Connect one to the T&P (temperature&pressure) valve to prevent trapping water inside the valve. This is not essential to the function of your water heater, but it is a safety precaution so that water flows freely from the T&P valve.
    • You should also use a plastic-lined nipple if you install a combination anode rod (see Anode Rods).
    • Lastly, if you have or wish to install a curved dip tube inside your water heater, you will need a 3inch long plastic-lined nipple to connect the curved dip tube to the water heater itself (see Knowing More about Dip Tubes).


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