I have never had any putty epoxy last in a pressure side leak.

I have found only one product that works to repair PVC and stands up well to pressure side leaks. It is called Plast-aid. I have used it successfully several times now and have not had it fail but it does take a bit of practice to get used to. It cures in about 15 minutes to repairs are fast.
http://www.plast-aid.com/
Their website has some excellent demo videos of how to use it.
The nice thing about it is that you can apply it as a glue or a putty so it can fill a crack. My only advice is use it outdoors if possible since the smell is really strong until it cures.