A water heater's tank is made of steel and plumbing lines are often made out of brass or copper. This poses a problem. Brass or copper may not touch steel without causing the steel to rust and corrode. The brass or copper will remain unharmed when touching steel. This can cause a weakened water heater lining. Plastic-lined nipples were created to deal with this problem. If you have a brand new water heater and it is attached to copper lines, check to see if any corrosion has occurred. If it has, you should have plastic-lined nipples installed immediately to prevent corrosive damage to the water heater which could cause a leak.

If you are handy with plumbing, you can install gate valves on your hot and cold lines on top of your water heater. Install brass valves into plastic-lined nipples. This is better than installing directly into steel. Don't attach copper or brass directly to steel or the steel will corrode and rust. Now you have the ability to turn the water on and off at the water heater.

Heat traps can be used where the plastic-lined nipples are installed. Hire a plumber to do this to increase the water heater's efficiency. Make sure adapters are attached to the copper plumbing. If the water heater has a combination anode rod inside, the plastic-lined nipple will still be important. Now you can attach a plastic-lined nipple. If you have a curved dip tube installed inside your water heater, you will need a three inch long plastic-lined nipple as well.

The easiest method of adding plastic-lined nipples if you have steel plumbing is as follows: Attach to both the hot and cold lines a plastic-lined nipple where the lines protrude from the wall. Attach to both of the hot and cold lines another set of plastic-lined nipples where the lines connect to the water heater. Use copper flex-connectors to connect the hot line from the wall to the water heater and do the same for the cold line. Heat traps should be installed to your plumbing lines for increased heating efficiency and to keep the water in the lines warmer.

Plastic-lined nipples may also be installed on the T&P valve. A lack of corrosion or rusting will keep the T&P working properly without getting any trapped water inside. This can assist, but it isn't absolutely necessary.