EXTERNAL PIPE LEAKAGE
DRIP! DRIP! DRIP! A leaking connector can perforate a hole right through the top of the tank, destroying the water heater. Even a young and well maintained water heater can fail if its pipe connections are poor.
Example: Galvanized or brass to steel tank.
Galvanized nipples are compatible with the tank connection dielectrically. Yet with an interior that is unprotected, the nipples corrode, clog and rust and eventually leak. Just as the internal tank is protected with glass lining, the nipple connected to the water heater should also be protected with a lining. Most water heater manufacturers are now supplying plastic lined nipples with new water heaters. To limit corrosion opportunity, install dielectric nipples at water heater connections and wall connections to put distance between dissimilar metals and reduce corrosion opportunities.
Although brass unprotected internally will not corrode like galvanized nipples, the introduction of brass to steel is not a dielectrically correct connection.Just as the anode being magnesium will corrode away to protect the steel tank, the unprotected area of the steel tank below the brass nipple will corrode to protect the brass nipple. To limit the introduction of noble metals to the water heaters, manufacturers apply a plastic coating to the copper probe on the thermostat and the temperature pressure relief valve.By reducing corrosion opportunities, the anode rods current is better directed to the areas where protection is most needed.
After maintaining 3300 water heaters SINCE 1987 and with repeat service being a large part of my business, I prefer a flexible connector for ease of future maintenance.Yet, where solid plumbing is code or a preference, I do not recommend the use of a dielectric union which so many plumbers use.The dielectric union consisting of a copper side and steel side separated by a rubber gasket. The steel side is internally unprotected from water contact.With time, that area corrodes and clogs restricting flow; just like a galvanized nipple. For best results, use a 3/4 FIP or MIP brass x 3/4“ compression union.Where galvanized fittings are exposed at the water heater, remove and replace with brass fittings to limit corrosion and clogging.Where gate valves are leaking or non closing, remove and replace with easy to operate 1/4” turn ball valves for ease of emergency shut down.To limit other corrosion opportunities, check for grounding of main water line — if not grounded, install a grounding rod with connection to the main water line. To stray current from the water heater, install a cross over from the cold line to the hot and to gas line using grounding clamps and #8 bonding wire on 100 amp service panels & #6 on 200 amp service panels.