Commercial water heater dielectric union

Discussion in 'Water Heater Forum, Tanks' started by Keith R, Jan 27, 2020.

  1. Keith R

    Keith R New Member

    Jan 27, 2020
    I'm the facilities manager at a not-for-profit youth center. I need to deal with three 1 1/2" dielectric unions (code requirement) on two 100 gal. water heaters. At least they appear to be 1 1/2". In each case a ring of corrosion has formed around the steel side of the union/galvanized nipple threaded joint. These joints each show a tiny leak at this point.

    What is the best way to confirm the i.d of the pipes without disassembling the system? Are they really 1 1/2" or maybe 1 1/4"?

    Can I replace only the galvanized nipple from the water heater body in each case and re-use the steel side of the union with a new flat rubber ring seal?

    Is there any likelihood that the galvanized nipples are actually attached to important inside parts of the water heaters (anode?)? Two of the corroded unions are bottom/side mounted inlets, one is the top mounted outlet. The outlet of one water heater shows no corrosion.

    If I have to replace the unions in total, I'd like to use Shark Bite couplings since the current press ring couplings don't leave a lot of room to work and I don't want to risk melting their O-rings by trying to sweat 1 1/2" couplers in the lines (my large diameter sweating skills are suspect anyway).

    Am I missing anything I need to pay attention to?

  2. Reach4

    Reach4 Well-Known Member

    Sep 25, 2013
    Presume the pipes are schedule 40. Use a digital caliper to measure the OD. It will be 1.66 or 1.90.

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