Best tape for tapered LP72 threads?

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MrVegas

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I'm going to take two old LP72s with 1/2 inch tapered threads in for hydro and visual pretty soon. I was just curious what tape people usually use on the threads when putting the valve back in the tank. (I'm not going to try to do anything myself, but I might actually provide the tape.)
 
I have been using 99%+ teflon tape intended for oxygen service. It seals much better than the thin white stuff in the plumbing department at the big-box home center.

The stuff I got is no longer available on Amazon, but here's the link. You might be able to find something similar:

https://www.amazon.com/Green-Thread...tape&qid=1549856633&s=gateway&sr=8-5-fkmrnull

Also, it helps considerably to chase the threads on the valve and cylinder with a die and tap to get the last of any crud out. Threadcutting is not in compliance with DOT regulations but my interpretation is that using a tap for cleaning purposes without cutting new threads is OK.

And I have had problems with them leaking when they come back from hydro, so your concern is not misplaced.
 
Also, it helps considerably to chase the threads on the valve and cylinder with a die and tap to get the last of any crud out. Threadcutting is not in compliance with DOT regulations but my interpretation is that using a tap for cleaning purposes without cutting new threads is OK.

I don't know anyone with actual tapered taps?
You can just go round and round with a dental pick too.
 
I don't know anyone with actual tapered taps?
You can just go round and round with a dental pick too.

Or a wire brush. You have to be careful to clean out any debris that falls into the cylinder.

1/2" NPT taps are available at any home center in the plumbing department. They are not expensive. 3/4" NPSM taps are more difficult to get.
 
I believe these are 1/2 nGt not npt.
They are close, but not the same.
I use a ss wire brush. Plumbing tape worked too.
Ymmv

Eta: I seen this spec'ed somewhere else but here's one. (At work)
SCUBA Valves | Dive Gear Express®

I meant to confirm when I pulled mine, but did not.
No way would I chase these with a npt tap/die
 
The only difference between NGT and NPT is the minimum number of mating threads. It's the same thread form, size, spacing, etc.
 

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