My house is 21 years old. Most of the gate valves no long actually shut off what they are supposed to. My house is plumbed with pex. I turned off the water at the street today and drained the house. I could not get the valve to screw out of the main shut off. I was pretty sure that I was about to damage something so, I gave up..for now. Then I looked at the toilet shutoffs. They are plumbed with pex and there's not that much pex sticking out of the wall to work with. The valves do not appear to be rebuildable. The main shutoff valve is visable by a round hole not much bigger than the knob.. How do I proceed to fix all these valves? What I'm thinking is to cut the pex on the main shutoff, splice in a few inches and add a ball valve. That's going to require cutting out a bug chunk of sheet rock. Then I suppose I'm going to have to cut that pex under the toilet tanks and just replace those valves. That wont leave much pex for whoever the next person is. I plan to but really good quality so I don't have to repair it again in my lifetime. If it's that close to the wall I'll splice in a section. I'm not a plumber as you can tell. I'm making this up as I go along.. Thoughts?