There are old supply hookups on my old bathroom faucet and I bought new ones and a new valve. The old ones are crimped on and I was told to cut them to take them off. I'm afraid I will cut the wrong section and I don't know what to do

Show us a picture.

Never heard of a crimped stop valve. There are threaded, soldered, and compression fit. Of course with PVC there is glued.

There are different type pipes, galvanized, copper and PVC.

After you shut off the water and drain the sink lines you can start here, for both hot and cold from the wall,

https://www.youtube.com/watch?v=HeEORnczD3s

I prefer to pull the whole faucet out, when I remove and install new supply lines because it's easier,

https://www.youtube.com/watch?v=5b9RgTXvlcU

No you don't have to disconnect the sink drain as the guy did in the video.

PS

Review these videos carefully FIRST, and compare them to what you have under your sink.

In the second YouTube video, installer installed P-Trap incorrectly.

Milo

After a little thought, I realized you meant that the supply tubes are crimped to the stop valves.

In that situation you don't cut anything. You replace both the supply tubes and the stop valves.

PS
I know plumbing can be contrary, stubborn, and subject to failure, but other than that, can you tell me how a faucet can have human like characteristics (anthropomorphic)?

Quote:

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Originally Posted by Milo Dolezal

In the second YouTube video, installer installed P-Trap incorrectly.

Milo

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Milo, what was his mistake? Just want to know.

Yep Milo is correct the P trap installed wrong the longer side should be connected to sink side and the small side to the drain side see the image below, Thanks.

John

Ah. I see that now. That's why I like this site.

Would it still work OK the way that guy did it?

Yes it works but the water level to seal the P trap will be low, Thanks.

John

Yes it will work, as long as you get the tail pipe down into the trap far enough for the gasket to seal. I have intentionally done this when the drain pipe that comes out of wall is too high (disposal installation).