Last year I closed my pool in late October and opened in early April. But my PH was off the charts and I think it affected my plaster. This year I want to make sure that I keep my ph in check. Could someone please point me to a pump (maybe on Amazon) that I could use to circulate the water during the winter when I peel my cover off a corner of the pool while I add Acid. And how long do I keep the pump running when I add acid to lower ph? I use TFT test kits so will check PH periodically to see what is happening. Do I need to circulate the water before checking Ph?