If it’s not cracked, you can just unscrew it and redo the Teflon tape and see if it’ll seal back up. Of course if you crack it, there’s no fix for that in time.
I drained it. It also sits under my insulated tarp with all the other equipment during freezes like what we're about to have. It usually holds above freezing under there.
I've tried the tarp thing, too. When we were anticipating 8F nights, I covered the pad about as well as you have, added some old moving blankets, even rigged a space heater to blow warm air under the assembly. I put remote thermometers inside and outside and never saw more than a 1F temp difference. I guess either I did something wrong or the tarp wasn't worthwhile. After that first night I gave up and everything was fine.
Perhaps it's just a placebo effect... or wishful thinking. It just always seems better to me to have it covered in times where it's going to stay below freezing for multiple days. At the very least, it keeps any freezing rain or snow off the equipment, which seems like a good thing. it's definitely a pain though.
