Gray Dump Valve Broke

This is the second time I’ve managed to break the plastic handle on the Gray Dump valve.  On the R172 both Black and Gray are plumbed to the “exit”.   I’ve loosened the black and gray hanger straps, pulled out the old gray valve, and now I'm to where I can’t get the new one in without turning the gaskets in or out of shape.  Just can’t get a 1” clearance so I’m thinking of dropping the pipe connection at the gray tank, place the new dump valve, reinstall the pipe at the tank.  At the tank there is a hose clamp and some type of soft caulk or putty.  Does anyone know what the putty is, or maybe a better way to attack this sucker?

Added note, R172 doesn't have anyplace to cut the pipe and install a union. Elbows, valve fittings, Everything are jammed together.

If you need to cut the pipe going into a fitting and need to reuse the fitting, there are reamers/cutters that plumbers use to get the old plastic pipe out of a fitting.  I was watching someone use one the other day.  I had never seen a bit like that before.  It was attached to a large drill motor with a right angle adapter.  I have no idea what these reamer/cutters cost.  It may be more economical to get a plumber who works a lot with abs pipe to give you a hand.