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Plumbing in the Home/gas water heater installation


Hi, thanks for taking my question.  I need to replace a 40 gallon gas water heater in my home.  It is slowly dripping and I want to replace it before it lets go. ( I have the water shut off at the heater and only turn it on when I need it, just in case it lets go, I will ONLY have 40 gallons in my basement instead of a flood).  My question is:  I have copper piping through out the house, however. above the heater there are two dialectic unions on the two water lines. and looks like two  2" nipple going into the top of the water heater.  What is the correct type of fitting coming out of the water heater.  Should I use a galvanized nipple or black nipple? Or is a copper nipple better? If so, do they make 2" threaded copper nipples? Your help is greatly appreciated, thanks again....Sam

Hi Sam,
Actually brass is best. The dielectric unions are crap and usually start to leak in a few years. In fact I would go with brass nipples and unions. Here is something like what I mean...use a 3" or so brass nipple and this;

The issue is galvanic reaction. Dissimilar metals in contact, like copper and steel create an electrical current which accelerates corrosion.

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Dana Bostick


Pretty much any residential plumbing questions. For "item specific" details such as a specific model of fixture, I will need to research and there may not be any useful information available. Note: I live and work in Southern California. We do not, as a rule, use hot water or steam heating systems, oil fired boilers or private water wells so my knowledge in those areas is pretty limited. There are others here on AllExerts that can probably answer those questions better.


Retired, Licensed General Contractor with Plumbing license. Active Home Inspector, Litigation Consultant and Infrared Thermographer, Online Marketing specialist.

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