iron to copper on hydronic system

**jfcl** · 03-25-2006, 09:06 AM

I've read here that a dielectric union is always required when joining iron pipe to copper pipe. My hyrdronic (baseboard) system is entirely copper except for the pipes at the boiler which are iron. The transition to copper is done with copper (or brass) fittings mated with iron fittings. No dielectric unions.

I know the water in a closed hydronic system becomes less aggressive over time but does that also mean that dielectric unions are not necessary? Thanks!

**Kristi** · 03-25-2006, 11:28 AM

Nothing will stop the inevitable electrolysis from happening (that I'm aware of, but I have not done and seen what many of the others here in the forum have yet!) other than a complete separation of the dissimilar metals from eachother... which a dielectric union does for you. There's no way I'd leave it like that, I would get the union(s) in there and preserve your system.

hj · 03-25-2006, 12:12 PM

Di-electric unions are more cosmetic than practical. The water is the medium for electrolysis to occur and a di-electric union does not provide sufficient separation between the two metals to prevent it. It has been years since I have installed a wet heat system, but I do not remember ever using dielectrics when I did. The isolation valves and zone valves usually provide adequate separation.

**Kristi** · 03-25-2006, 02:03 PM

Really, HJ? Dielectric unions are only cosmetic? I've put them in for a long time (as it's code here) but never thought they would be described as having no purpose at all. Now I want to go back to the jobs a decade and a harf ago and case them out!

Not entirely off topic, but I just encountered a nasty bit of electrolysis yesterday... the electrical is grounded to the service copper line, and the PRV is just a crusty mass of rust - it was barely identifiable! It's amazing what level corrosion can get to in a short few years...

**master plumber mark** · 03-25-2006, 02:19 PM

they make the customer feel warm and fuzzy--thats all

if you were to actually take one apart after about 3 years you

will find that they usually corrode shut lots quicker than just

copper male adapters gong into a water heater.....

I honestly dont know if I would install them on a boiler or not

all they are going to do is eventually restrct the flow through them and

I suppose thay can take theheat??

Kristie ---where have you been>>>??

havent seen you post here in ages

**Cass** · 03-25-2006, 02:20 PM

I once worked on a 4 story apartment building that would develope 4-5 dialetric leaks every year.

I searched for the cause and never could find the source.

I had that account for 4 years, lots of fun, and almost burned it down once. The only time I have ever come close to doing anything like that and the only damage was to my hand.

**Kristi** · 03-26-2006, 08:24 AM

WOW! well, I can say that this is a prime example of why this forum is such an invaluable tool (definitely for me). Where else could tradesmen tap into so many other tradesmens' experience? I haven't had any reason for follow up over the years on my installations, and since it's in our code I just don't even question them - which is quite unlike me

MPM, I'm now known as the Preggo Plumber! I had 3 solid months of ******** progesterone poisoning (morning sickness) and have barely dragged my ass back to work only in the last 8 weeks! Let me tell you, the smells that come with service work DO NOT go well with early pregnancy! I only have 3 months left before life changes forever... problem is, I'm a career woman! So you'll see more of me for the next couple, then I'll probably disappear for another couple, then I'll definitely be back