Dielectric unions


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Old 10-28-05, 01:03 PM
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Dielectric unions

I am repiping my munchkin 140. On the inlet and the outlet of the boiler I am using carbon steel fittings then connecting to 1 1/4 copper pipe. Do I need dielectric unions between the steel and the copper? I am using the steel because I already have them and copper fittings are to expensive where I live.
 
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Old 10-28-05, 03:00 PM
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Any time you mix dissimilar metals such as copper to steel, you need di-electric fittings. If not, electrolosis will occur. This eats away at the metal and shortens the life of the pipe. It is noticeable in the form of a white crumbly substance at the joint where the two surfaces meet. Good luck.
 
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Old 10-28-05, 07:34 PM
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Risking getting roasted & eaten

I am going to disagree with the dragon. Most dielectric unions will not take the heat of a boiler. In 20 years, I have never used, nor seen, dielectric unions on a boiler. Copper & steel are joined all the time without problems. It may be a problem on potable water but it does not seem to matter on a boiler.
 
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Old 10-28-05, 08:01 PM
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Grady,
I'll not roast nor eat you. Plumbers of any type are not tasty, even with ketchup.

The wonderful thing about this site is that you can learn new things everyday.

Some places the Dielectric unions are code, my area is one of those.

jkgordon

You can use a brass or cast iron fitting as they do not react with the copper or steel.

Since you are in Canada, check with your local authority to see what is permitted there.
Good luck
 
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Old 10-28-05, 08:19 PM
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Dielectric unions

Majakdragon is right about the brass & cast iron. Of the two, I would prefer brass. Do check with your local governing body as to code.

If being a plumber will keep me from getting roasted, I guess I'll have to pretend to be a plumber when I'm really not. I'm just an old rode hard & put up wet HVAC'er who happens to be a wethead.

Dielectric unions on boilers are code? Never heard of that. Is that Arkansas state code or something local?
 
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Old 10-28-05, 08:44 PM
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Grady,
The dielectric unions I was refering to are brass on one side and steel on the other. I was not refering to the plastic looking connectors used on home water systems. These obviously will not hold up and could present a dangerous situation.
 
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Old 10-28-05, 08:52 PM
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Dielectric uions

Majakdragon,

Thanks, I don't ever recall seeing one. I'll have to ask at one or more of my local plumbing supply houses. Like you said, learning something new is a great thing about this site. That's part of the reason I'm here. Thanks again.
 
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Old 10-29-05, 12:26 AM
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Thanks guys. I have put them on hot water tanks before but I wasnt sure about using them with glycol.
 
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Old 11-01-05, 01:19 PM
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So on an indirect hot water tank: are you saying that you can use a brass fitting in between the tank taps and the copper pipes instead of dielectric unions (I am talking about the cold feed and DHW taps)?
 
 

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