AVOID Plumber Costs and STOP Water Leaks By Doing This! 

Plumber here, one to many unnecessary steps. You had enough space to use 1/2" closest cutters for the new dishwasher cut off valve, and always clean and sand the portion of pipe you're crimping onto. Teflon is not needed on the outside threads of the compression stop/supply line they use a rubber gasket to make it water tight, I use pipe dope on the brass ring itself for a even seal.

Who else laughed when he put the cup down there to catch the water??

Just tighten the big nut behind the handle and also use a wrench to hold the valve body at the same time 99% of the time that will stop the leak

👍🏼💕

DIY is the only way to go my man!! Only comment or question I have is why not put a rag down to catch all that water coming our of the old compression valve? =)

Also, the plumbers tape is "teflon tape" and you should wrap it 3 to 4 times around the threads. While it can help prevent leaks, its main purpose is to help you screw both pieces togeather. Pipe dope is used with teflon tape to provide the "seal" to prevent leaks. =)