Stacie, others in your area might have another opinion, but unlike the true northerners who can see major freezing for weeks on-end, those in your area (or mine at times) see those winter blasts that hit at night and the morning hours and usually tend to not last as long or be quite as severe as other parts of the country. The problem with that is while the water surface may not freeze, parts and equipment around your pool can. Last winter, even some southerners who never close experienced problems with the unusually bitter cold - usually equipment related. Some used to get-by with simply leaving the pump on to keep water moving so the lines won't be able to freeze. But if power goes out, your pump's freeze protection kicks in, or water simply stops moving for some reason, things get tricky. That's when the freezing begins and swelling occurs. Even waterfalls can be tricky if water gets in those joints and swells.
I suspect you'll find a mixture of opinions about N Texas closing, some who close and others who don't in your area. If you chose not to close, I would consider the following:
- Keep water moving during those hard freezes
- Have a way to cover or protect the equipment pad to keep the freezing rain/temps off the equipment. Consider a drop light under outdoor plastic and blankets/tarps to help insulate and retain some warmth.
- Wrap above ground PVC
- Consider covering your waterfall if possible so that water doesn't seep into grout/mortar and swell/crack.
- Have some scrap pool noodles available to cut and place in the skimmers just in case.
The lines underground should be fine. But having a contingency plan with those items noted above can come in handy.