Dielectric Unions, circulators, etc.

Paul Pollets

DE unions or nipples are not needed in a closed loop hydronic system. Black malleable unions are fine and won't leak.

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Jean-David Beyer

Dielectric Unions, circulators, etc.

My hot water heating system has many metals in it. Aluminum heat exchanger, steel plumbing in the boiler, steel pipe near the boiler, copper pipe elsewhere (finned tube baseboard upstairs, copper tube radiant heat downstairs, indirect water heater).I have Taco 007-IFC (cast iron) circulators in the copper tubing.

To avoid electrolysis problems, it is often suggested to use dielectric unions at connections between the different metals, but this does not seem to make sense in the case of the cast iron circulators because the circulator motors are electrically connected together by the green wire (ground) connection, as is all the copper tubing, so all those fancy unions (if I had any) would be defeated by the common electrical connection.

So am I missing something? If the grounding of the electrical stuff shorts out any insulation provided by the hypothetical dielectric unions, is there any point to using them?

Jean-David Beyer

Thank you.