Question just about the order of pipe dope sealant and teflon tape

Yes. I did not use that RectorSeal No. 5 stuff for my PVC.

In fact, it appears NONE of the "pipe stuff" I own is correct for PVC; so I will try to find the Spears Blue 75 thread sealant at the irrigation supply places on Monday.

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And, in the future, if I'm forced to use Teflon tape, I'll use this method of wrapping the tape properly:

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Reply to
Danny D
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I should correct that slightly, by saying I read and understood Oren's and DD_BobK's recommendation of the best being the Tplus2 pipe thread sealant.

The only proscription against that stuff, based on the Vic Smith article, was the fact it also lubricates as it seals.

However, if I keep to the finger-tight-plus-two-turns rule, I should be safe with the Tplus2 stuff.

I'm going to remove all the fittings, and try again.

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Reply to
Danny D

On 5/12/2013 12:18 PM, Danny D wrote: ...

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I typically just use a little permatex blue silicone or the like. Yeah, it's a little slick but just don't overdo tightening and you're fine.

Another that works fine is a white lithium; same thing as for usage. I have even just used a little ol' gun grease when other wasn't handy and it was.

Reply to
dpb

Just because the recommended red stuff works as a lubricant doesn't mean it's not the right stuff. Virtually ANY sealant will "act as" a lubricant.

Reply to
clare

Just because it is a lubricand doesn't mean it is not also a sealer - and vise versa. If all you need is a lubricant, just oil the threads and see how well it seals - or grease the threads. It is a combination product.

Reply to
clare

It doesn't matter what order you apply them in, as long as you apply the first properly, and NEVER apply the 2nd.

Reply to
Larry W

You still have to apply the correct one first.

Reply to
krw

Please quit saying that's "my article." I didn't write that, I just cited it. I have no experience at all with threaded plastic pipe. And I'm not buying all this emphasis on "lubricate vs non-lubricate." As long as it's compatible with the plastic, seals the threads, and doesn't harden up, it should work. "Overtightening" because threads are lubed makes no sense to me. One guy's "feel" for tight isn't the same as another's. You use a different length wrench, the feel changes. Likewise, these guys are saying stuff like "2 turns past finger-tight." That fine if there's no burrs on the threads, the threads are consistently formed, and everybody has the same fingers. That's not realistic. What's more realistic is a consistent taper and consistent thread count. You want to look at how many threads should still be exposed for a good fit, and tighten to there. lube or no lube. I can see that with galvanized and know when the male is inserted far enough . The force used to get there can vary depending on the thread condition, but threads exposed is the best indication of what force the taper is putting on the female, and when to stop cranking down. Anyway, that's how I'd approach tightening plastic too. But until I did it, it's still a guess to me.

Reply to
Vic Smith

It does to me.

The less force needed to overcome friction, the more force you have available to tighten the joint. Try slipping a bicycle handle bar grip onto bare chrome plated handle bars and you'll see what a fight it can be. Now, lubricate the handle bars so the rubber grip slides over a thin film of oil, and you'll see what a difference friction makes.

It's like a car. The more power used to drive the power steering pump, the air conditioning compressor, the water pump and the alternator, the less power you have left over for turning the wheels.

Reply to
nestork

What does any of this have to do with tapered pipe threads?

Reply to
Vic Smith

I ended up using the 2-in-one lubricant + sealer, after taking pains to remove all vestiges of the Teflon tape.

BTW, do we lubricate the unions?

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I think they go on dry ... but I also thought Teflon tape was to be used on the threaded fittings (and that was wrong).

Reply to
Danny D

Here are the exposed threads on what I ended up with on the schedule 40 fitting:

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And here are the exposed threads on the schedule 80 nipple (this is the one that I had the Teflon tape + sealant) after I removed the Teflon tape and sealant due to what I read in this thread - and started over:

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Reply to
Danny D

UPDATE:

Given the wonderful advice in this thread, I ripped out all the threaded fittings today, and started over - this time with *just* the PVC sealant+lubricant (and specifically, *no Teflon tape*).

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On this second pass, I put only a bead of paste on the threads:

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I then tightened the fitting two turns after hand tight:

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I also replaced the schedule 40 fitting by putting the sealer on:

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I wasn't sure how thick the sealant was supposed to go on though:

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As instructed, I then screwed the fitting on only hand tight:

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I used a pipe wrench for the last two turns after hand tight:

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With this being the end result:

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Reply to
Danny D

Except if you follow instructions and tighten the specified 1.5? turns after contact it doesn't matter how much or how little friction there is in the joint. the specified number of turns after contact will ALWAYS give the same fit - and the same amount of thread deformation or fitting swell.

Reply to
clare

HB-

Please provide sight / link for following.....

""One of the defining characteristics of PTFE (Teflon) is how good it is at defeating friction. The use of PTFE tape in tapered pipe threads performs a lubricating function, which more easily allows the threads to be screwed together, to the point of deformation, which is what creates the seal."

Reply to
DD_BobK

Reply to
DD_BobK

I should add to be clear....

NPT threads need a sealant to seal the spiral leak path. NPT threads do not seal by thread deformation.

Hint: To do a practical proof of want I knew to be the design intent of NPT threads, I did the lube alone assembly of NPT pipe & fittings.... they leak no matter how tight. :( I used oil so that no "sealant" was present. :)

cheers Bob

Reply to
DD_BobK

Are the union threads NPT also?

Reply to
Caryn

You can put some silicone lube on the rubber o-ring. That is what seals it. Nothing goes on the threads.

Reply to
trader4

I think we all understood that's what he meant.

 I have no experience at all with threaded plastic pipe.

I agree. For that matter, Teflon tape is widely used and if it made a huge difference, there would be leaking fittings everywhere. Yet, lots of people, including many pros are using tape.

Imagine pushing a v shaped wedge into a v cut opening in a piece of plastic or metal. The further in the wedge goes, the more splitting force you have. Do you think with the same amount of force applied to the wedge, it will go in further with or without lube?

Agree. That's where experience counts. And why perhaps those with little experience could wind up in trouble using Teflon tape while others have used it and it's worked fine.

And there I disagree. Joints are tight when they are tight. If you try to rely on looking at how many threads are showing, I think you're in for trouble. How do you even know that the number of threads is consistent from one pipe to another? For example, if you get a piece of pipe cut and threaded at HD, is piece A going to have exactly the same number of threads as piece B? You just have to develop a feel for it and learn from experience.

Reply to
trader4

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