How to drain outside PVC lines to protect freezing

Pol17772730
by Pol17772730
We are in Texas where it seldom gets to 1 degree as I did earlier in the week.
Our new house is well protected. We have one outside faucet from the house where an electric light is left burning under a tub.

The old water well is a distance from the house and it has two shut offs...home and outside water. We must turn the water on to fill animal troughs daily and off to drain when it get really cold.

We were told it was necessary to only open the lowest faucet on the line. We did leave hoses connected to other faucets. Obvious mistake! We will disconnect all hoses in the future.

I guess my question is if each faucet must be drained separately or if only the lowest is necessary to drain. Will leaving the lowest open allow all of the others to drain down as well?