Dialectric or not

[Deleted User]

is neutral to both copper and steel, and is an accepted methodology under most codes.

You wouldn't be using plain steel in an open application. Make sure all tube in the system has an oxygen barrier, otherwise it acts like an OPEN system...

Avoid red brass because it has a higher content of copper and is therefore less compatible with steel pipes.

Di-electric unions actually set up their own electolytic cell causing internal corrosion to the point of complete blockage. I do not use them unless I can't find the alternative, and brass valves for the transition betwixt copper and steel is ALWAY an option.

One section of the code that bugs the crap out of me is the REQUIRED use of unions around items like boilers and tanks. The consumer see's the union and get's a mental image of velcro in their mind and starts thinking, "HMMMmm, I DON'T need a plumber.. I think I can do this myself!" Then, when they get the tank home, and find out it is 6" shorter than the old one, they stack the tank on shaky bricks, thereby creating a huge water/gas/CO vent/ possible flood and fire exposure. Kids get to horse playing in the basement, and one of them bounces off of the tank and knocks it down, then you've got REAL problems. And kids are prone to not tell their parents EVERYTHING that happened in their day. And when confronted about it, they plead ignorance.

I tell the inspector that if they don't know how to cut and re-solder pipes, that they probably shouldn't be messing with it... 9 out of 10 will let the union rule slide.

For the record, I've seen HO work that far exceeded most contractors...

ME

Jason_41

Dialectric or not

Does black iron fittings to copper need a dialectric union? I have gotten answers both ways. Maybe somebody here knowsthe right answer. What about black iron pipe to brass? Any and all responses would be greatly appreciated.

Rich Kontny_3

Jason

Typically not a problem in a closed loop system as the entry of fresh oxygen via makeup water is minimal. On open systems such as potable water (hot and cold) protection is necessary. Di-electric unions are usually not the best answer as they tend to leak after a while.

With pex or plastic systems this of course is not a problem.If you are refering to a closed loop heating system I would not be overly concerned. Might want to test the water for quality reasons though as I have seen acidic water tear apart boilers and their distribution systems.

ALH_4

Galvanic Corrosion

I haven't seen any issues with iron to copper, but if you are particularly concerned you could use a dielectric nipple instead of a union. The unions tend to leak. Actually, they almost never fail to fail.

bob young

can't go wrong with a flange union