When to use Dielectric i.e. IDWH, Boiler

Jack Waller

Have been reading intently for months and now it has reached the point where I must install my system in my acreage home. Many thanks to all the generous contributers.
I have thrown out my old basement and main floor furnaces and HW tank so I can use my chimney to vent my Trinity Ti150. I will use a mainfloor fancoil and a combination of fancoil and radiant in my walkout basement, plus I have the IDWH and a radiant shop floor of 4 loops - 1000 feet 1/2 pex. I hope sometime in the future to have more radiant but right now this is too expensive a retrofit. General advice would be much appreciated.

I will have many questions but for now a couple small ones.

1. Where do I need dielectric unions

2. My RTV52 SS IDHW has a warning about having to use loctight sealant on connections to, I assume, stainless nipples at the tank. Is Teflon a no no?

Jack in Edmonton Oiler country

Brad White_74

Dielectric Separation

Jack, note I did not say "dielectric unions". They have an annoying tendency to leak on long weekends when you have company over. I prefer bronze ball valves or a 4-inch long brass nipple. Victaulic Dielectric Waterways are also effective. I am sure that there are other means and methods out there; this is just what I specify and use.

Where do you use them? Wherever you are connecting dis-similar metals such as copper and steel or especially galvanized steel and copper and in the presence of an electrolyte, water in this case. (Brass and bronze seem to break the dielectric issue for reasons which have never been fully explained to me. They work, old timers swear by them.)

Essentially two metals in the presence of an electrolyte create a current. The less noble metal (steel in a steel-copper match-up) is an anode and will corrode, sacrificed in the process. Stray current such as an errant active ground, will accellerate this process. Some steel-copper joints have lasted for years without incident, same with copper and cast/malleable iron. I do not know why.

I cannot speak to the specifics of teflon. There have been abundant threads (so to speak) on screwed pipe dopes, wicks and tapes which may be beneficial to you.

hr

The new Grundfos iso-flanges serve as

true dielectric seperation with the plastic ring.

Personally I don't see a dielectric union fitting anywhere in a hydronic system. I'm not sure any are rated for that temperature potential.

However some inspectors still insist on dielectric unions at boiler connections. Go figure.

Actually I don't like dielectric unions on any of the potable water side either. Plastic lined dielectric nipples, even the funky copper flex tubes are better than DE's

hot rod

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Unknown

those

Those dielectric unions are worthless in my book and experinces, true u may have electroliss problem with two differnt metals however, I have never have problem if u use the male copper fittings into the steel fittings, never use the female copper over the steel pipings..... I never use them on heating systems...
Plumbing, only when the codes required it so it pass the inspection and then I replacedthe leaky connections with 2 years time, with all copper connections... I NEVER seen a directed male adt into water heaters leak...

Couderay

Dielectric Unions

They seem to have a love hate relationship with many people I have had good and bad luck with them on boilers and hot water heaters alike. Copper to steel be it galviized, or stainless I like to use them, even on steel piping. They are on my boiler outlets and inlets. Yes they have leaked put a little never seize and it helped. My mothers boiler eats them for lunch. So for her I used brass valves off the inlet and outlet and went right to copper. Teflon tape is fine but I use rector seal for all my joints, it works for me.

Jerry_15

Right on you guys. Dialectric unions (and for that matter galvanazed pipe)are one of the biggest scams ever foisted on the trade and the public, and it wouldn't surprise me to see them outlawed some day. Not soon enough. There is no need, or place for them on a closed loop system. Even the plumbing trade has gone gone to cop flex connectors for water heaters. Think about it; a cheap plated steel connector, the only advantage of which is a rubber gasket for quick connection. I don't mess with unions much anymore, since it's far quicker to saw it out and press in a coupling. I have taken out more than a couple of water heaters where the only corrosion/restriction is at the union. I have also cut into 100 yr old houses where black pipe was used for DHW for the feeds. Clean as a whistle. The galve was a horrorshow. The only fittings that cannot be used on a closed-loop are galv. Brass to black, ok. Copper right to black (I'll hear about this one), or to a valve, ok. A nice brass nipple (on DHW) and a valve solves all. Otherwise black is beautiful, and code too.

gerry gill

i'd personally not use dielectric fittings

as they will themselves become a future problem..i agree with Brad and the others..our code allows a brass interface with a steel/copper connection..it works..the reason sometimes you see a dissimilar metal connection (copper to steel) lasting for years and years on a potable sytem is because there is something else more anodic in the system that is currently sacrificing itself to the copper (cathode).. in my case my copper connection directly to my potable water heater after 12 years shows zero signs of corossion..why, because i'm on my fourth anode rod in that period..i just replace it every so often and it places a more anodic substance into the system...this is my argument against copper return piping on steam boilers..the system is open to the atmosphere so the condensate gets oxygen, and to make matters worse, carbon dioxide, its hot, which acts as an accelerant, and there is the dissimilar connection to the boiler..people say, ''hey the coppers lasting fine''...no joke..its the cathode..its the boiler thats getting an accelerated death..

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Jerry_15

If you're on your fourth anode rod I would take a look at ground connections from electrical close by. This bonding was required by many local codes, and is a disaster. AC creates spectacular electrolysis, especially when it's close to the equipment. I've never figured out the reason. Lightning strike perhaps? They used to even bond it to the gas lines, but gave it up, I think. Dialectrics suck. A couple of brass nipples will do the job. Even a dirrect copper connection is better, as you have already figured out.

gerry gill

i've been changing the anode

more because i want to than because i have to..i just do it as normal maintenace..but your right i think..i've wondered also about the required hot to cold to gas bonding wire..it itself creates an electric path for dissimilar metal corrossion.

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Unknown

how do u want, Gerry?

How many anode rods u want Gerry? I have a whole bunch of them here, I have to take the rod of water heaters prior puttin them to service on well water system, otherwise u will get rotten egg smell soon after the installion... Shorten the life of water heater? Nope, water heaters last longer on treated well water system than city water.... Why?

gerry gill

they last longer?

us city plumbers are being jipped, hehe..i don't know squat about wells...must be some serious water treatment..what about dissimilar metal electric current? thats what the anode was fighting against..doesn't that happen with well water?

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