How long should I wait to turn on the water, after gluing my pipes together?
30 degrees Fahrenheit is a bit cold for happy PVC gluing, IMHO. You might want to apply some (non-open flame, given the solvents) heat to the joint before gluing and while it's curing. Also be absolutely sure that the pipe is dry, or else use the "damp-tolerant" PVC glue (usually blue.) 

A temperature range of 40-100 degrees F is recommended by the glue manufacturer They note that it is possible to get a strong joint below freezing, but that extended time is required. If you can safely heat it, do. 6 hour cure time is specified for your pipe size and temperature; that can be shortened to an hour above 60F (assuming water pressure is below 180 PSI....)

I do seriously question using PVC at all in hot water service - that's what CPVC is made for, and I have personally used hot water to bend PVC pipe. If you can borrow the tools from someone, I'd actually look into replacing as much of it as is easily accessible with PEX, these days.