Any plumbers here?

[Bonnewagon]

I need to identify the thread on a piece of inch and a half diameter brass pipe. The type that is used on tub shoes, overflows, sink drains, tail pieces, etc. It is a fine thread but how many threads per inch? My problem is I have an old cast brass "Y" that was used for a tub drain and an overflow. Both ends are slip joint and are that same fine thread. I am re-using the tub drain for another tub but I want to use the old overflow as a clean-out. I need a cap to close off that end but I can't identify the thread. It looks like this.

 

[Tomeal]

If you want to use it as a clean out, you could put a fernco cap on it. Wouldn't ruin the threads.



This isn't exactly it, but you get the idea what it is.

 

[wonderboy24]

i am a plumber. i dont think you will find a cap due to the threads. i would say to find a pluming whole sale company and see if they can match it up. but i dont know of a cap to fit these threads

 

[Bonnewagon]

The Fernco is out. This is for a clawfoot tub that is in my 100 year old bathroom restoration. All will be exposed. Wonderboy do you know what the thread count might be? I found NPT: 6 tpi, it is not. NPT Fine: 12 tpi maybe. And NPT Extra Fine: 20 tpi maybe. That is what was in threads on various forums. Worst case I may take the old brass slip collar nut and solder a brass or copper disc to the top and use it as a cap.

 

[Bonnewagon]

OK, I just woke my old brain up and remembered that I had a Sears tap and die set buried down the basement. It had a thread gauge. So the extra fine thread on the pipe I showed is 28 tpi. Yikes, I didn't expect that. But the thread on the ancient "Y" is 16 tpi. And that I never even heard of. Hmmm, I have a Rigid threader set. I am pretty sure I can re-thread the brass "Y" to 1-1/2 x6 NPTM pretty easilly.

 

[fleming442]

Not a plumber, BUT I do know hot is on the left, cold is on the right, and shjt flows downhill!

 

[Bonnewagon]

My specialty is making it flow UPHILL! Anyway, scratch that, the 1-1/2 threader was too big and the 1-1/4 was too small. A 1-3/8 fitting?!? Oddly, the end that was lead wiped into the lead P-trap was 1-1/2 x 6 tpi on the outside. A modern cap fits right on. Too bad I need that end for the drain. And it was threaded the 1-3/8 16 tpi on the inside. So I can actually use the modern cap and just glue it to the fitting with some BoatLife or Marine Tex. If I ever need to access a wrench will undo it toot sweet. Here is what I am dealing with, a very tight squeeze, and I don't want to open any more floor than I have to. The hole was left by the last installer.

 

[Bonnewagon]

I think I got it. I wrapped the threads with Flex Tape (as seen on TV!) and then compressed it with a hose clamp to get it embedded to the threads. Then I removed the clamp and wiped inside the modern cap with silicone grease so it would not stick to the Flex tape. Then I screwed it on just enough to cut it's own threads in the tape. It seems pretty secure I just hope it doesn't leak. But I have fixed swimming pools with the Flex tape and it is some amazing stuff.