Re: Alkalinity and pH drifting down when normally drifts up.
I had the same problem last week and found the cause of my problem in an unexpected place....A critter in the return line....ph was drifting down, not up as usual with the SWCG. I also noticed my CL would crash to near zero every couple days, causing me to add bleach to supplement the SWCG. When the pool started to cloud (July 3rd, with 50 people coming for a party on the 4th!), I popped the top off the sand filter, thinking I could have channeling through the sand, as this was a problem for me in year 1 of pool ownership (this is year 3), back when we let my son's Labrador retriever swim every day. The dog is now banned from the pool and channeling wasn't my problem, this time. It was a MOUSE! As I adjusted valves at the pool pad, a well-bleached mouse carcass came through the line and got caught in the pump basket. Apparently, the strainer in my skimmer basket had become dislodged at some point and the mouse was sucked into the skimmer return line, where it remained trapped at the junction for quite some time, given the look of the remains. Since removal of the mouse fixed the problem, I'm blaming the little critter. I guess the lesson is that organic matter can get into the strangest places in our pool systems and can be difficult to find and remove. The mouse was small enough to get sucked into the skimmer, but too big to get past the partially closed valves at the equipment pad. Part of my routine going forward is to fully open skimmer and return lines from time-to-time, so anything caught in the valves can flow on by....
The good news is that by catching the problem early on, the water cleared overnight and we had a great 4th of July Party with a sparkling pool! My pH is back to drifting up a bit, as normal, requiring about 16 oz. of MA a week to keep it right (the only maintenance chemical I need!)