Upgrading To Plastic Lined Nipples Can Help Keep Your Water Heater From Rusting

Steel will rust when it comes into contact with brass or copper.  Hot and cold water lines on top of the water heater are often made out of brass or copper.  The water heater's tank is made of steel.  When they are connected together, the steel tank rusts and weakens while the brass or copper connections do not rust at all.  Dielectric unions and plastic-lined nipples were invented to defeat this problem.  We will discuss plastic-lined nipples in this article. If your tank is installed with copper only pipe nipples touching the steel tank, you should replace them with plastic-lined nipples immediately.  Don't panic though.  Unless your water heater is brand new and only a few months old, there won't be a damaging corrosion problem.
If you are handy with plumbing, you can install gate valves on your hot and cold lines on top of your water heater.  Use brass valves and install them into plastic-lined nipples instead of directly into steel plumbing.  Do not install it to the steel plumbing directly or it will cause the steel to rust.  This will allow you to have positive control of your water lines at the water heater itself.
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 you have a combination anode rod installed, the nipple you choose is very important as well.  Install a plastic-lined one if at all possible.  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.  Make sure to have heat traps installed as well for increased heating efficiency. Plastic-lined nipples may also be installed on the T&P valve.  This keeps the T&P from getting any trapped water inside and allows it to flow out of the T&P for your safety.  This is not essential, but it can help.