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I'd like to retrofit our shower with a rain head by attaching a Kohler K-76331-CP diverter to where the current shower head comes out of the wall, then having one of the diverter's connections go to a regular shower head, and the other connection to the rain shower head. The diverter connection that I'd like to use for the rain shower has male threads labelled G1/2B.

Valve Diagram

Normally this connection would point downward and have a hand-held shower hose attached to it. What I'd like to do instead is have that connection point upward and attach a rigid 15-in pipe to it (e.g., a 15-inch nipple) to feed the rain head. I called Kohler, and they said that there's no problem pointing the connection upward. But I'm not sure how to join that G1/2B output to a rigid NPT pipe.

Is there a coupling I can use, or is there some other method of doing this--for example, a 15-in pipe that would have a G1/2B female connection on one end and an NPT male connection on the other end?

  • This site looks like it has several diverters that come with two NPT outputs so you may be able to avoid the whole adapter situation. – JPhi1618 Jul 9 at 16:11
  • Thanks for the links. Looks like a lot of good diverters on that site, but I'm a little confused about the input connection. Some say IPS and some say NPT, yet both are supposed to connect to a standard shower arm. Are they just using the terms interchangeably? Thanks. – Dennis James Jul 10 at 15:02
  • Technically, IPS (Iron Pipe Straight) and NPT (National Pipe Thread) are different. IPS is straight like the BSPP threads and NPT is tapered. Strait/parallel threads are designed to seal on a washer of some sort whereas tapered threads are designed to be self sealing as they tighten. They will not provide a good seal if they are used together. Some people mistakenly use the terms interchangeably. – JPhi1618 Jul 10 at 15:09
  • IPS and NPT threads are similar enough that they will usually seem to thread together correctly and in some instances might give an ok seal with a little help (teflon tape, etc). – JPhi1618 Jul 10 at 15:11
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The G in the thread size looks like it denotes a British Standard Pipe (also known as BSP or BSPP) size of 1/2". For whatever reason, Kholer decided to use this size on their hand showers, and that's what this valve is designed for.

You would need to find an adapter such as this one to convert to NPT. This listing mentions shower fixtures, so that is promising. The title and description contradict each other on which side is BPT and which is NPT, but the product images look like it's what you need (they show female BPT threads).

Here is another possible adapter, but not chrome plated. If you are in the UK, you may be able to find a BSP to NPT adapter easier.

  • Sorry for all the link edits. I think I've found a good product link on Amazon now, but I can't guarantee it will work, because I've never needed an adapter like this. – JPhi1618 Jul 9 at 15:56

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