Are there any rules as to how far tees and other couplings and connections have to be from each other? I have a drain tee that is leaking and I need to replace it with a new tee. The problem is there is another tee right below it like 2" so if I cut the tee at the top and get a new tee to put in there I will only have 2" of pipe left to use to push into the new tee when I cement it together. Is it better just to remove both tees and separate them by like 6' it is ABS drain and vent piping. Thanks

Are there any rules as to how far tees and other couplings and connections have to be from each other?
No!

if I cut the tee at the top and get a new tee to put in there I will only have 2" of pipe left to use to push into the new tee when I cement it together. Is it better just to remove both tees and separate them by like 6' it is ABS drain and vent piping. If the tee in question is at the base of the run it would simply give the pipe more slope.
If it wouldn't present a problem I can find no fault with close coupling the two tees, Just be sure slope is maintained. Good luck, Tom

I agree with Tom. As long as you have enough pipe to glue new San T on, you are fine...