Found a leak under my bathroom sink. I think it is a simple one to fix, but would like some backup as I am a newbie at this.

There was no moisture above the joint pictured (see below). You can see a water drop at the right hand side of a threaded section of pipe by a shutoff valve -- the handle is just out of the frame, but you can see the flexible supply line connection nut. Ignore the tilt of the picture -- it's the best I could do in a tight space.

Anyway, it appears as though this is just a simple threaded joint. I removed the supply line and tried to tighten the (Brass Craft) valve onto the short stub of copper pipe, but I couldn't get it to budge. I was using a super short wrench, and I was kind of nervous to apply too much torque since I don't know what the h*ll I am doing -- it took several minutes for me just to figure out what kind of joint I was looking at. It seems as though I could just:

- shut off the water supply to the house
- open a hose spigot, which is lower than the joint in question
- remove the supply line from the valve
- remove the valve from the copper stub
- clean the threads
- apply a generous amount of pipe dope (maybe an insufficient amount was used originally?)
- tighten the valve on again
- close the valve
- reattach supply line
- close hose spigot
- turn on water supply to the house
- open up valve, try faucet & inspect the joint

Is that right? what tools will I need? That is a super short stub of copper pipe to work with! Will I hurt the joint on the left where the copper stub goes into the 90-degree elbow when I do this?

Any other advice is appreciated.

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