I built my darkroom without running water, but a zink and running water just outside the door to the darkroom – call it the lightroom!
I could easily have installed running water into the darkroom, but decided not because of the following experience:

A long time ago I had together with some friends a marvellous huge darkroom including “everything”. But those of us who weren’t into mass printing “cards”, but rather making a few prints with some ambition towards the “perfect print”, were all the time running in and out of the darkroom in order to view the print in full light, and do some thinking how to proceed.

In view of this I realized that the important thing with a darkroom wasn’t a wet darkroom but just a DARK room ☺. Nothing wrong with water in the darkroom, but if you want to view your prints in full light you could as well have water and washing trays in “the lightroom” – of course nice to have it very close to the darkroom. Your eyes adjustment to the darkroom light will not disappear that easy, unless you don’t do tooo much thinking how to proceed next!
I always keep clean water in a 20 liter plastic container (with a tap) in the darkroom, just to have water at darkroom temperature easily available.
/Bertil