Teflon tape or pipe dope for PVC threads for underwater enclosures?

[bltpyro]

I am making an underwater light with PVC piping. I have a threaded cap to access the battery. Would it be better to use teflon tape or pipe dope on the threads? Does one or the other do a better job of sealing? In my mind, unscrewing would mess up the teflon tape, but I'm not too familiar with it so I'm not sure. Also, is it enough to just use the tape/dope, or should I add something extra to prevent leakage? Thanks

[FredT]

PVC pipe threads do really well to seal in internal pressure when properly packed and not disturbed. not so much so repeated assembly and dis-assembly with external pressure on them. Teflon tape may be a better choice since it can easily be removed and replaced at each dis-asembly event.

The best bet would be to figure out how to install an O-ring seal on a threaded plug. Should only be a couple minutes with a lathe to modify a female threaded adaptor and a hex plug to take a suitable o-ring just below the hex, similar to an SAE O-ring seal joiint.

[Keysdivers]

Teflon tape is the only approved thing used on pvc threads.

[lazybean]

IF you are going to do it, Tape. Ether way you will have to clean and retape every time. I personally would not.

[miguelitro]

Tape is cheap, you can keep a roll in your car for on the spot battery changes, it easy to clean off and reapply, and yes it is the only thing approved for PVC. Pipe dope is not what you want.
Mike