Leaking Washing Machine Compression Valve

[tiddlywinks]

Hello. We had a leak in our washing machine compression valve. We bought a new valve but couldn't get the original nut off so we used the new valve but with the old nut. Unfortunately it's still dripping from the nut. Wondering if the olive inside the nut is damaged, or is the drip more likely coming from the join between new valve and nut? We didn't use any plumbers tape, should we have? We're obviously worried about forcing the nut and causing a bigger problem.
Any advice appreciated. Thanks!

 

[Wayners]

Cut olive carefully.
Hacksaw blade going carefully and slow..
Hold blade in hand if you want.
It's soft brass so cuts easy.
Create a grove.
Flat end screwdriver in the grove and twist to split olive.
Replace nut and olive after cleaning pipe.

Don't use anything aggressive to clean pipe.
Kitchen green side nylon sponge or something as you don't want to scratch copper.
Do not overtighten. Just be gentle. Better loose Vs dog tight.
You can always tighten if it leaks but unlikely.
People tighten too much and it can leak