Wait, what? I should be keeping my PH higher in winter? I just tested today and noticed my PH had dropped from 7.6 to 7.4 and my TA had dropped from 100 to 80. I just thought they were seekin equilibrium.
Full test results
FC 7 (added bleach to get to 9)
CC 0
PH 7.4
TA 80
CYA 90 (working on this over the winter to get it down.
What is the logic to maintain a higher ph in winter? How much higher?
I'm going to caveat my answer to say that *MY* experience is with SWG and plaster, which is not your pool type. Other forum members with more experience can round out and/or correct me if I'm wrong.
As you may know, there's a pool water measure called CSI (Calcium (Calcite?) Saturation Index). Its components are pH plus adjustment factors for temperature, total alkalinity, and calcium hardness. There's also a constant (12.1), which is an adjustment for Total Dissolved Solids. I would be wise to point out at this point in time of my response that the use of CSI is not an agreed upon "test" or value in pool maintenance. Discussion has been made both for and against it's use, both here and on other forums for years (I've seen ChemGeek's posting on other forums on this topic as far back as 2008)
*I* use CSI as a general guidance to ensure that the holistic view of the water chemistry is correct. The target is slightly negative, so slightly "aggressive" water. Note that aggressive is often confused with corrosive. The original CSI work focused on predicting the precipitation of calcium scale and not corrosion of metal.
Since one of the inputs to CSI is temperature, as your pool water temperature decreases, your CSI can change as well, becoming more aggressive (negative). However, since the most direct influence is pH, letting it drift upward in colder water, "compensates" for the temperature and restores the CSI to balance. That point was the key for me to understanding the difference between summer and winter maintenance.
If as BuckeyeCrhis said, you play around in PoolMath, you'll see that one way to keep your CSI "constant" year round (in other words, if *I* was focusing on keeping it at about -0.2), is to adjust the other parameters that influence it such as pH and TA. You wouldn't want to play with Calcium Hardness because that's going to involve draining water at some point in the switch between warmer and colder water.
As for the specifics of how much higher on pH, likely not much. No more than a 7.8 target in colder water whereas warmer water you may be targeting 7.5 to 7.6. The difference in CSI between a pH of 7.5 and 7.8 is a contribution of 0.28 on a 30,000 pool.
Like I said, *I* find it useful for *me*. I am in no way telling you to adjust your maintenance techniques to start using it. For *me*, CSI provided a solid basis for understanding why winter pool maintenance targets for *my* pool were different than summer targets. I'm an engineer and wanted to understand the "why" as opposed to just 'do this at this time of the year'.
Nothing I've said is intended as a post against any other member/topic/thread in which CSI is discussed. I'm simply relating *my* understanding and application of its usefulness to *my* situation.
