adding a shutoff valve

No one but a person on the site can tell if there is any play in the line.

You can use a "repair" coupling in conjunction with a short piece of pipe and your valve to add play to a line where there is none. Repair couplings are bigger than normal and do not have a stop so they can slide over the pipe and then return to the proper position. Pencil marks on the cleaned copper can help with the alignment.

Unions work also.

We can't see your basement from here. It may or may not have enough flex, depending on how long the run is, how pipe is fastened or wedged, and how long the runs are past the first elbow in each direction. Grab the pipe and try to move it, before you cut. Copper is generally more forgiving than old galvanized would be, but there is still a slight risk of causing problems elsewhere anytime you flex old pipe runs. Eyeball the whole run with a flashlight and your fingers, looking for green spots and such that can indicate minute leaks and weak spots.

I need to do the same thing in my basement, to add a tee for the icemaker, to replace the vampire tap valve that I am scared to touch. One of these days....

-- aem sends...

------------------------------------- Beauty of copper is the options it gives you. Cut it where it works best you. Sometimes Ill even take out to a 90 if ones close (solves the flex problem). I agree with using repair couplings if needed (I never have one when I need it). If I can I like to sweat the valve on my pipe sections at the truck and then sweat the pipe section in w/the valve on it at the couplers or fittings as they sweat fast and easy in close quarters and valves dont. Mainly with new guys I notice a tendency to think small and cramped when for a few extra feet of pipe they can work out in the open. Keep in mind you have to get the torch in there to

Marco

quick answer - "it depends."

You can buy sweat fittings without dimples in the middle so they can be slipped completely over a pipe. if you find your pipes are constrained, this is what they're used for - make a cut in the pipe, brighten it up, then you can just butt the cut ends together and slide the fitting over the cut and sweat as usual.

I'd buy a short length of 3/4" pipe just to reduce prep time, then you only have to really clean up two cut ends instead of four.

nate

Solder a stub of copper pipe in each end of the valve first. Then you don't need any play at all to solder the assembly in place using "repair couplings". (just a normal coupling without a stop in the middle -- be careful to center it)

Bob

We can't see it from here, but very likely your piple has enough flex. Copper piple is rather forgiving. Ball valve or gate valve is good. Globe valve has too much resistance to water.

Maybe, every situation is different. Generally the more length in the pipe, the greater the flex. You may get more leeway removing a support, etc. My last resort is using a sleave coupling, but it is an option often used in tight places.