just seen matts post and i think this is a valid point as i know what can happen to RO's in the frost
on a serious note, last year when it got that cold, i had my ro in the garage but with the doors open, i went back to it after the frost , i heard "drip drip drip" i was like hmmm, lets go see, the frost had smashed all my pre filter housings, i had no water i was absoulty gutted, so quickly ordered them, lost a few days pretty much a week i think
THEN...i got them, fitted them, mint i thought, but oh no, water fine though prefilters, looked saw water piddling outta somewhere looks again and it had smashed the membrane housings!!!
i was not impressed and lost about 2 weeks to that!
PROTECT YOUR RO's