Valve thread sizes

[Akimbo]

A failed tank is also a great way to display a vintage regulator.

 

[kombiguy]

A failed tank is also a great way to display a vintage regulator.

Yep! I have a non-functioning Nemrod Snark III double hose just waiting to be put on the tank and displayed! Maybe rotate it with my Healthways gold label doube hose.

 

[Leadking]

I picked up a 4 steel 72s the other day for a pittance. In the process of cleaning them, I found out that one had previously failed hydro, and the serial number was Xed out. Still a bargain for the rest. My question is really this:

If a 3/4 straight thread valve bottoms out in the neck with about a 1/4 inch or so remaining to be screwed in, is it a safe assumption that the neck of the tank is a 1/2 NPT?

Are you under some form of medication? If I understand your post, you want to put condemned tanks back in service. Do the world a favor and scrap them.

to help those of you who are curious, they are old pipe "tapered" threads.

 

[Akimbo]

… If I understand your post, you want to put condemned tanks back in service. Do the world a favor and scrap them...

Not exactly, he plans to use it to display a vintage regulator, not dive with it.

… to help those of you who are curious, they are old pipe "tapered" threads.

Half inch CGA threads, which are very similar to tapered NPT (National Pipe Threads in the US), was the standard before straight thread O-ring sealed valves came into use in the late 1950s and early 1960s. I still dive two 72s with tapered CGA threads. One was born in 1959 and just keeps passing hydro. There were a couple of other straight thread O-rings sealed threads but the 3/4" straight pipe is the dominant standard in the US.