amoses said:
Occasionally it gets down to freezing, and once in a while it will get into the 20's, and on very rare occasions it will break into the teens. But the cold never lasts long and sometimes you will even see 70's in January, although that is not normal either.
The pool guy said you just have to make sure that you run the pump continuously when it is cold, is that true?
My inground pool has a "freeze-protect" function that runs the filter and waterfall (maybe even Polaris) pumps when the air temp gets down to some preset temp, maybe 37 degrees, maybe 47 degrees I'm not certain but could check if you want me to. The particular temperature may have to do with the natural rock waterfall that can develop cracks from even small amounts of ice forming over night with radiant cooling.
Without that automatic feature, I'd probably run the filter overnight or whenever they were predicting a "hard freeze -- protect pipes" or even a "possible freeze -- protect tender vegetation". What you want to do is to be certain that the relatively warm pool water is circulating through pipes that are small diameter and exposed to cold winds and possible radiant cooling (which is what can create ice on puddles even when air temp did not get to 32 overnight)
You probably also will want to check the pool water temp on occasion but my above ground pond hardly ever got ice on it and it was only 300 gallons and in shade mostly and ran a fountain all the time so it cooled way faster than a big pool ever could. That pond was at 40 to 55 degrees or so most of the winter. I think I only saw ice on it when we had that big freeze in what, 1988?, when we hit 7 degrees and stayed below freezing for a day or 2. Anyhow, what I observed was that the pool would be at something near the avg of high and low temps of the prior 2 or 3 days. So, since most of our winter (Houston) has daytime temps about 55ish and night temps about 35ish, the pond would be at 45ish then.
I'm not sure where you are in Texas, and I do know that Ft Worth or Midland is way, way different than Houston, but what you mentioned about the range of temps sounds like Houston so I expect you don't *need* to close the pool.
OTOH, a cover will reduce your need for chlorine over the winter no-swim months and may reduce the amount of leaf litter you collect. I sometimes wonder whether I'd like a winter cover just to keep the leaves out, but my "better-half" insists that he loves the look of the water since we can see the pool from every part of the house.