Threaded PVC - Teflon vs Sealant

[hiimsean]

I'm planning on gluing my PVC tonight, pending the arrival of my gate valve today, and I came across a thread on RC about teflon tape. Some recommend against using teflon tape on threaded PVC and using thread sealant, like this

 

[hiimsean]

There's a few threads with in-depth posts against it. Most are that teflon is truly designed for metal threads, if used on PVC it can become hardened and eventually leak.

Continuing to dispel the myth concerning the use of teflon tape:

Lasco tells everyone (an overview on their website) that teflon tape is improper/inappropriate for use with pvc threaded fittings. It deforms the threads, however slightly, and the threads are what provide the greatest portion of the sealing (taper/tight fit.) Teflon tape lubricates the threads which is counter-intuitive as it encourages overtightening.

You need to be using a non-hardening thread sealant, that does NOT contain teflon. Visit Lasco's website, and get the truth, rather than searching "creative solutions" from within the hobby or plumbing in general. The information is pretty straight foward and not difficult to comprehend.

To quote:

"Teflon tape, Teflon paste and pipe dope is intended for metal pipe and fittings. Metal to metal fitting joints are more difficult to tighten than plastic; the surfaces tend to gall without the aid of such lubricants as Teflon or pipe dope. Plastic fittings do not need this lubrication.

When Teflon tape is wrapped around plastic male threads it adds to the strain and tensile stress. The tendency of most installers is to incorrectly wrap several thickness of tape around the male threads, increasing stain and stress further.

Teflon paste and pipe dope, just like Teflon tape, make threaded joints slippery. Their use on PVC fittings can be an invitation to over-torque.

When working with threaded plastic fittings do use a proper sealant. The right sealant for threaded joints is non-hardening, compatible with plastic and doesn't add slipperiness."

http://www.lascofittings.com/threads">http://www.lascofittings.com/threads</a>

And from Sprears:

"Paste-type thread sealants fill the threads better than tape. Application is less critical"

Reeflo specifically states in their instructions not to use tape on the connections to the pump.

The myth concerning teflon tape is spread by both journeyman plumbers, and so called "master plumbers" as well.

The excessive need to disassemble the plumbing after it is installed, is quite overdone. You are far better off, doing the plumbing right the first time and solvent welding, then you don't have to take it apart to redo it&#8212;or even to service it.[/QUOTE]

[IMG]http://reefcentral.com/forums/showthread.php?t=2166384&page=2&highlight=threaded+pvc">http://reefcentral.com/forums/showthread.php?t=2166384&page=2&highlight=threaded+pvc</a>
[IMG]http://reefcentral.com/forums/showthread.php?t=2341423&highlight=threaded+pvc">http://reefcentral.com/forums/showthread.php?t=2341423&highlight=threaded+pvc</a>

 

[giulianom]

I'd just use thread sealant.

The general rule of thumb for PVC threads is to tighten to finger-tight, and then use a strap wrench to tighten it no more than 1-2 turns.

The problem with PFTE tape is that it's a lubricant, which makes it too easy to tighten - resulting in fittings that are overtightened and can crack.

PVC threads are tapered... so if you tighten them too much, you'll stress the housing which can lead to a crack.


I've read good things about Rectorseal #5, which is what I plan to use on my threaded connections soon.

 

[hiimsean]

Thanks. I'll pick some up today!

 

[elfloyd]

Now you tell me...!