I've read out here somewhere the valves usually fail first in freezing temps.
With highs of 25, you could be in for a hard freeze. I'd see if there was a way to introduce some of that antifreeze to surround the valve.
The outlet pipes to the holding tanks fill first. The heat tape mentioned prior is a good way to combat that problem.
I have tank heaters, likely because the rig came from Oregon. I don't do cold weather myself.
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