# Leak at dielectric/insulated union



## TheEplumber (Jul 20, 2010)

Add 2 or 3 wraps of teflon tape on top of your pipe dope. And yes, IMO you should have unions on equipment


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## Plumber26 (Nov 10, 2010)

I always use tape only or tape and dope, but never dope by itself on water connections. Just never had much luck with it. 
And the dielectric union is needed to keep the dissimilar metals from touching (copper and galvanized) so they won't corrode on another. And it'll make the next replacement a breeze.:thumbup:


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## Work4living (Nov 28, 2010)

I agree with the other 2 posters. Lots of people even pros think the coated nipples are enough. They aren't. If you are using channel locks maybe switch to a 14" pipewrench.


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## thewoodguy (Oct 27, 2010)

*Thanks*

Yep, dope, tape and a 14" pipe wrench was the magic combo! The guy at Home Despot did try to talk me out of the dielectric as unnecessary, but I stuck to it.

Thanks, guys, and Happy Holidays - ours will be with our new water heater!


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## handy man88 (Jan 23, 2007)

Ok, if one were to use both tape and dope, which goes on the thread first?


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## Work4living (Nov 28, 2010)

Dope, tape, and dope.


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## thewoodguy (Oct 27, 2010)

*order*

I did tape on the male threads, dope on the female. And lots of it!:thumbup:


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## Plumber26 (Nov 10, 2010)

thewoodguy said:


> Yep, dope, tape and a 14" pipe wrench was the magic combo! The guy at Home Despot did try to talk me out of the dielectric as unnecessary, but I stuck to it.
> 
> Thanks, guys, and Happy Holidays - ours will be with our new water heater!


 
Remember; the guy at the Home Depot is simply just a guy at the Home Depot. If he had any knowledge of plumbing, he would not take the pay cut just to work at the Home Depot.


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## TheEplumber (Jul 20, 2010)

handy man88 said:


> Ok, if one were to use both tape and dope, which goes on the thread first?


You can't convince me one way or the other, but I put dope on first then tape. Used to do it the other way but I worked a job that had a lot of dirt around my pipe so I put dope on first, then tape. This helped keep the dirt of my threads. Been doing it that way ever since :yes:. And I always use both


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## handy man88 (Jan 23, 2007)

Work4living said:


> Dope, tape, and dope.


Wouldn't dope first result in slop under the tape? Isn't the purpose of tape is to have a nice, snug fit on the threads to prevent slipping?


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## TheEplumber (Jul 20, 2010)

handy man88 said:


> Wouldn't dope first result in slop under the tape? Isn't the purpose of tape is to have a nice, snug fit on the threads to prevent slipping?


How much dope do you put on? JK, Yes, that can happen but a little less dope helps. Why pile it on above the thread heigth? Besides, there are several types, Real Tuff, Megalok, Grip, Rector seal, etc. Some are thicker than others and receive tape easier. Put your tape on first if you want, its not a fireable offence:thumbup:


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## AllanJ (Nov 24, 2007)

Both tape and dope are supposed to get squished between the pipe threads and fill enough of the thin empty spaces in between that water cannot leak.

In many cases, if a taped joint leaks, undoing it and putting more tape on for the next try will be better.


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## Ltnicks (Nov 9, 2010)

the unions I have installed had a rubber gasket between the connection, is that there?

I do tape then dope. no more than two wraps of tape


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## Work4living (Nov 28, 2010)

Look, the misconception is that everyone thinks tape or dope seals threads. They don't.
Their function is a lubricant, they reduce friction to allow the threads to be tightened together and also aide in the loosening. My experience has been tapers in threads male & female do not always match. I usually about 95% of the time use teflon based soft set pipe dope, it isn't cheap. Blue Magic, Select Unyte, Rectorseal, & Gimme the Green Stuff are brands I like. When the dope won't work then I use thin layer of dope then tape and dope again. This practice has never failed me in 29 years.


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## handy man88 (Jan 23, 2007)

Work4living said:


> Look, the misconception is that everyone thinks tape or dope seals threads. They don't.
> Their function is a lubricant, they reduce friction to allow the threads to be tightened together and also aide in the loosening. My experience has been tapers in threads male & female do not always match. I usually about 95% of the time use teflon based soft set pipe dope, it isn't cheap. Blue Magic, Select Unyte, Rectorseal, & Gimme the Green Stuff are brands I like. When the dope won't work then I use thin layer of dope then tape and dope again. This practice has never failed me in 29 years.


I agree that teflon tape and dope reduce friction to allow better tightening and loosening of fittings. But, I also think they serve a sealing purpose as they fill any voids where there is no thread to thread contact. After all, we're not using tape/dope on NPT threads which do have some sealing function even without tape/dope.


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## Work4living (Nov 28, 2010)

I'm lost. We are talking about plumbing, dielectric unions sealing the joint of the union and nipple. They are npt threads.


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## diy888 (Jan 18, 2009)

*"sealing"*

The origin of a lot of confusion about "thread sealing" has to do with the twofold nature of the sealing.

1. Tapered NPT threads must form a leak-tight seal against each other.
2. The threads must be sealed against corrosion (because ultimately a corroded thread cannot maintain a leak-tight seal). This is especially important in transitions, e.g. from iron to copper, even in an ostensibly "closed" system, because variations in pH level (resulting from frequent fresh-water fills because of leaks or overpressure situations) can make the closed system resemble an open system.

A sealing-cord such as Loctite 55, for example, will help to create a leak-tight seal from day one but will do nothing to seal the threads against corrosion over time.

So you have to be clear when phrasing the questions: 

Will this product help the thread to make a leak tight seal against the opposite thread?

Will this product seal the thread against corrosion? 

Will this product and that product used in tandem do both?

Can such-and-such product used alone do both?


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