The shutoff valves under my kitchen sink are busted. The hot is stuck open and both generally look bad. I plan to install new ones while replacing the hose attachment. Furthermore, the cold water utility valve is leaking. I have quite the work ahead of me. CY: You should find out if the pipes coming out of the wall are copper, or galvanized. Do the shutoffs sweat on, or thread on? That will affect things.
I think I've located the water main. There's a large-diameter PVC pipe poking out beside the driveway. If that's not it, then I guess I'll have to call the utility company. CY: Probably in the cellar, if your h ouse has a cellar. Or in a cabinet some where.
One way or another, the water main has to be shut down while I do most of the repairs--the hose can come after the new valves work. CY: Since you have to work on it, get em both at the same time.
I'm curious how the water heater plays into all of this. The last thing I need is water--especially the hot water--sprayed into my face when I pull the old shutoff valves. CY: If you shut off the water main, then the next thing is to open the lowest faucet (probably the laundry sink in the cellar) and leave them open while you're working. That will reduce the chance of leaks.
Is there anything I need to do in relation to my hot water heater to complete the shutoff? CY: You don't need to close any water valves for the WH. But, it's a good idea to shut off the heat source. Electric WH, shut off the breaker. For gas WH, turn the white knob (on top of the gas valve) from "ON" to "PILOT". And remember to turn it back on when you're through.