I just realized that my hot water 1/2" copper inlet in the kitchen is terminated with a regular single oulet valve but I do need to share it between the faucet and the adjacent dishwasher. Is there a way to do it without uninstalling the regular fitting with some sort of splitter that mounts on it or do I need to just remove it and install a double outlet fitting?
There are adapters you can screw on that give an additional tap for the dishwasher. The size needed for the dishwasher connection is fairly standard (3/8 compression thread) as it is common to run 3/8" o.d. copper tubing or a braided stainless flex connector with that same thread.
What is NOT standard is the existing valve's outlet size (it can be any one of, like 4 different sizes). You will need to either have someone with experienced eyes take a look at your existing valve, or remove the existing supply line and take it to the plumbing shop with you.
Here is an example of a double outlet valve that you can buy at Home DEpot, Lowes, OR most any stores that sell -plumbing supplies. The inlet end comes in a variety of sizes and configurations. Just go to the store a explain what it is that you are trying to do. I looked this up on the Home Depot website (BrassCraft 1/2 in. Nom Sweat Inlet x 3/8 in. O.D. Comp x 3/8 in. O.D. Comp Dual Outlet Multi-Turn Valve). I also found this valve on Amazon---Eastman dual/outlet dual handle stop valve.---"hope this helps"