How to plumb clawfoot stop valve (straight vs tapered threads)

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Jcpitre

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The stop valve connector is 1/2 FIP. If I am not mistaken, it means it has parallel (straight) threads.
I thought I could use a pex to threaded male adapter. But I can only find ones with NPT threads, i.e. tapered.
I kind of read that connecting these two would not be watertight.

What is typically done for plumbing these kind of installations?

I don't really want the PEX to be visible poking through the floor.
I tried using a drop ear elbow, that is NPT, under the floor, then connect a nice chrome 1/2 in pipe to poke through the floor and connect to the stop valve to that.
But in that case the pipe has both sides with MIP, i.e. straight. So the connection with the stop valve is perfect (MIP to FIP), but the connection with the drop ear elbow leaks a bit (MIP to NPT).
People at the HD don't even seem to know that there is tapered and straight thread. Maybe I am overthinking this and I just have to be more generous with the teflon tape? Or maybe there s such a thing as a male NPT to FIP adapter? (I looked and could not find).
 

John Gayewski

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MIP FIP are both NPT. One is male iron pipe one is female iron pipe. Both are tapered.
 

Jeff H Young

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If the abbreviation was 1/2 " FSPT that would be female straight pipe thread . kind of unusual mostly you see MSPT on like faucet connections like the bottom of a lav faucet and the nuts that use cone washers hand held sprayers have a washer in bottom that does the sealing.
I can only believe what you tell me you have and here is a short solution DO NOT screw a straight threaded nipple into a tapered thread fitting, its not proper . change something or attempt some tricks to get it to hold but I don't recommend that . find compatible fittings is best
 

Tuttles Revenge

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All of your threaded fittings should be tapered threads. Starting with your drop ears, they need to be securely mounted. The pipe nipples thread into those and should protrude from the floor enough for the escutcheon plate to cover and have at least the threads showing above. The stop valves then thread on top of those and should also be tapered threads. If any part is not tapered threads, replace them with better quality.

I had to hook up a clawfoot recently that one of our guys installed. Their installation was so dead nuts on that all I had to do was cut everything to lenght to hook up the tub. No bending of any supply tube, just straight up.
 

Jeff H Young

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mip and fip are both npt or nspt . youve got something wrong but dont get caught up with the letters you know what a male and female is . If you have some kind of tubing connections there could rarely be a straight thread like supply lines on a lav . but starting at floor a threaded 90 with a nipple then a stop valve should all be Tapered threads sop whatever you do buy all new stuff whatever it takes get the right parts. you can call them whatever you want but you want tapered pipe threads
 

Jcpitre

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Sorry for the confusion. I thought FIP stood for female IPS. You comments got me thinking though, and I went and rechecked the stop valve fitting. And it is NPT. My bad.
I suspected it did not make sense that HD people had no idea of the difference between NPT and NPS. It's because most nipples and fittings are NPT, so they don't think about it.

I initially got an IPS nipple instead of NPT. Got rid of it and got an NPT brass nipple. And it's fine now.
I just wish I could get an chrome plated nipple. The big box stores don't carry them apparently.
Thanks everybody.
 

John Gayewski

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Ips is iron pipe size. Which is also npt. Think about it. National pipe taper. What are they tapering? Iron pipe.

Brass, stainless, and pvc/abs are also ips.
 

Tuttles Revenge

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Chrome nipples are available on build and other online vendors.. they're pricey.
 

Jcpitre

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Ips is iron pipe size. Which is also npt. Think about it. National pipe taper. What are they tapering? Iron pipe.

Brass, stainless, and pvc/abs are also ips.
Very confusing.
I did check (with a caliper) the IPS nipple I initially got and the thead appeared straight. And it leaked when connected to a NPT elbow.
The NPT nipple I got afterwards does not leak.
 

Jeff H Young

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It gets confusing I may be calling some of these wrong myself. NPT taper NPS straight threads are correct abbreviation Sounds like jcpitre on track though glad to hear
 

mmdougherty

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Most clawfoot tub valves have straight threads and are connected using a bent tailpiece and either gasketed or ground joint taper connection.
Hi I have a clawfoot tub with a faucet that is a wall mount that S-union with 1/2" male NPS end. I cannot find a 1/2" female NPS fitting for water use. I would like to use a 1/2" female fitting that could be mounted inside give the faucet more stability I looked up some of the items you mentioned and really couldn't find the right fitting. The flexible hose is the only thing we found that fits the S-union. Unfortunately that can't be mounted.
Most clawfoot tub valves have straight threads and are connected using a bent tailpiece and either gasketed or ground joint taper connection.
Your comment was the most helpful as it addressed the NPS fitting where we are having the problem. But not sure what those other pieces mean (bent tailpiece, gasketed or ground joint taper connection).
 

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