# When to use teflon(or pipe dope)



## shed-n-deck

I've been told that when you use plastic(cpvc or pex) that there is no need for pipe sealers like teflon or pipe dope, also, I've been told that when you use soft metals together (like brass on brass) then you don't need it....What are the rules for using thread sealers?


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## newguy07

jjj


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## newguy07

I don't think your info is correct on the soft metals.


Also, pipe dope is before teflon tape.


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## Kingfisher

Not sure what you mean by "pipe dope is before tape". I still use dope and tape but never at the same time:whistling I use dope for all gas fitting and every now and then on older water pipes. New metal pipes is usually tape and I use it litely on pvc too.


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## KillerToiletSpider

shed-n-deck said:


> I've been told that when you use plastic(cpvc or pex) that there is no need for pipe sealers like teflon or pipe dope, also, I've been told that when you use soft metals together (like brass on brass) then you don't need it....What are the rules for using thread sealers?


On plastic to metal joints, as well as brass to brass joints, you should use both, tape first, with dope on top of the tape. Plastic and brass are both easily deflected, the taper on the thread can change the shape of the base material, so the tape fills the void in the deflection, and the dope seals it as well as making it a bit easier for the next guy to take apart.

In any case, I both tape and dope all my joints, especially when doing galvanized water pipe (Yes that is still installed on remodel jobs in some high rises), the only exception being gas, I only use dope on gas pipe.


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## Plumber

I agree 100% with Killer


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## Cole

KillerToiletSpi said:


> On plastic to metal joints, as well as brass to brass joints, you should use both, tape first, with dope on top of the tape. Plastic and brass are both easily deflected, the taper on the thread can change the shape of the base material, so the tape fills the void in the deflection, and the dope seals it as well as making it a bit easier for the next guy to take apart.
> 
> In any case, I both tape and dope all my joints, especially when doing galvanized water pipe (Yes that is still installed on remodel jobs in some high rises), the only exception being gas, I only use dope on gas pipe.


Good Information To Know, Thanks!:thumbsup:


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## MinConst

yea Killer that is good info. Never used both at the same time but will remember this one.


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## Herk

I use teflon tape occasionally, but more often pipe dope. I like Rectorseal more than the others, and #5 Special if I can get it - it's the gray dope that is easier to get off your hands than the yellow #5 regular. When teflon first came out, I remember it being a lot thicker - they advertised that you could tape a thread with a gouge through it as deep as the thread and it would seal. I never quite believed the hype. 

Teflon has its uses, and I would usually prefer it on plastic threads, but if you read the usage on the cans of dope, you'll find that a lot of them are now safe with plastic pipes. (You wouldn't want to use linseed oil-based pipe dope on plastic!)

I have also found that some dope works far better than others - Rectorseal won't bind when joining brass and copper, others will. Teflon sometimes makes joints move too easily after they're installed, which may cause later leaks.


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## shed-n-deck

Well, that's great information...I never thought about using both together, I always thought of it as a one or the other situation....Thanks for the information Killer, and the recommendations Herk.....


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## JamesNLA

I too tape and dope every threaded joint. I do however use gas Tee tape and dope for all my gas joints. And not trying to sound too arrogant but I don't have leaks....just don't. Wait, once on a new gas service I did about a year ago. I cracked a tee fitting, i guess I over tightened it, but I thought it was bad. I had a leak when I pressure tested...but not from the threads!!!


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## Tom M

I thought teflon was primarily used for dissimilar connections in material like iron to copper or something. I see the value of it in other places as explained above.


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## Ron The Plumber

Never use pipe dope only on plastic threads, reasons are it makes the threads too slick and will cause you to over tighten the joint, as other have stated tape and pipe dope together will give you a positive seal the first time with little to no chance of it leaking.


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## MechanicalDVR

JamesNLA said:


> I too tape and dope every threaded joint. I do however use gas Tee tape and dope for all my gas joints. And not trying to sound too arrogant but I don't have leaks....just don't. Wait, once on a new gas service I did about a year ago. I cracked a tee fitting, i guess I over tightened it, but I thought it was bad. I had a leak when I pressure tested...but not from the threads!!!


You cracked a mallable tee? You do know that cast iron isn't allowed for use on gas piping?


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## JamesNLA

MechanicalDVR said:


> You cracked a mallable tee? You do know that cast iron isn't allowed for use on gas piping?


What? Who said anything about cast?


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## The plumber

From what I understand pipe dope is more of a lubricant to help you get a tighter fit. I rarely use teflon because it's not messy enough for me. I do use teflon and pipe dope together when working with galvanized or black iron. FYI--- NEVER SCREW A METAL PIPE INTO A P.V.C FEMALE FITTING NO MATTER WHAT YOU USE. I'm tired of removing cracked female adapters from meter nipples.


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## PARA1

*why ky*



The plumber said:


> From what I understand pipe dope is more of a lubricant to help you get a tighter fit. I rarely use teflon because it's not messy enough for me. I do use teflon and pipe dope together when working with galvanized or black iron. FYI--- NEVER SCREW A METAL PIPE INTO A P.V.C FEMALE FITTING NO MATTER WHAT YOU USE. I'm tired of removing cracked female adapters from meter nipples.


This fear may have something to do with your last post about always having a tube of *KY *handy:w00t:


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## skyhook

I first read about using both in a post by Ron the Plumber. Been doing it ever since with excellent results. Thanks Ron. :thumbsup:


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## POOLMANinCT

blue loctite dope is my fave, lubes & never had a leak w it. & for guys with less experience, they seem to do better vs. tape. fyi I never do gas pipe.

ray


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## The plumber

POOLMANinCT said:


> blue loctite dope is my fave, lubes & never had a leak w it. & for guys with less experience, they seem to do better vs. tape. fyi I never do gas pipe.
> 
> ray


blue loctite works on wet threads also, unlike most thread sealants.


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