This will be the third year that I will drain more than half my house of water supply. I know how; my question is timing. Each year I take a little more risk, because I have to give up use of my washer, and now is not the time to move it. It's in the part of the house I heat, but the water winds around in a crawl space under an addition that I close off. The addition contains 2 full bathrooms and a sink in a tiny kitchenette, one bath and the k-nette on the 2nd floor.
The addition is easy to close off, because the adjoining walls are insulated, and all I have to do is put a 2" foam panel across the hallway.

The plumbing, all copper, goes 25' from the shut offs along the full cellar, and disappears into the crawl space under the addition. (I won't/can't go in the crawl space to add a valve just for the washer!)
No fixture in either bathroom or the kitchen sink is in an outside wall (keeping in mind that there is only a tiny amount of heat, if any, leaking into the addition).

So can any pro tell me how cold the outside temperature has to be (and for how long) before anything freezes, approximately?
The ground still has summer heat. I suppose even the building has some. And the days run in the 40s, 50s, and even 60s. Last night it was 27. I got by.

I won't hold anyone to whatever you say! THANKS