We had to remove a Kohler shower valve because it was leaking, and are now
Having trouble replacing it with a valve that fits the available space. The
Old valve was a Kohler 42049. That part is no longer available, and is
Replaced by Kohler 78655. Unfortunately the external diameter of the 78655
Valve body is larger, and it has male connectors (rather than female on the
42049), making it too big to fit the available space in the wall. We have
Not been successful in finding a valve assembly (from either Kohler or other
Manufacturers) that is as small as the Kohler 42049.

The available space from the center of the hole in the wall to the nearest vertical joist to the right is 2.5". This must fit the shower valve and a 90 degree elbow. The Kohler 42049 was 2.5" across and the elbow was just over 1" - so it was already a tight fit. Piping is 0.5" copper.

Any suggestions?

If I am not mistaken, the "male" connector is also a sweat connector. If you have copper plumbing then slide 1/2" copper pipe inside and solder it as it was any other copper fitting.

Milo
Wouldn't that be a 1/2" copper street 90?