I need to change the lower of the 2 valves. Is it possible to change just the one or do I have to buy out the whole thing and start over?

Cut the pvc a couple of inches below it and then it should all unscrew. Join it back with a glue in coupling when your done.

Thanks Chris! Why didn't I think of That?

Think I'd do them both while I was in there already.

Although not a must in this application, nothing works better at cutting PVC pipe than a oscillating power saw. Not sure if that's others call them, but I'm referring to the type of power saw with small, flat blades move back and forth as if they are vibrating more than sawing. You can easily reach into tight areas to cut a pipe when you could never maneuver a hand saw.

Use gate valves. Change both.

Too late. Home depot only had 1 valve.

or to make it even easier, cut the PVC a few inches down and use a compression fitting

Not trying to start anything, but are you serious about using gate valves ?

Absolutely! Those are shutoff valves not flow regulators. You're flooding. Do you want a quarter turn gate valve or a three turn flow restriction valve?

What kind did I put on?

You used a ball valve. That's the right one. A gate valve is the kind you screw for ever and then they start leaking a few years later.

Thanks again Chris.