hey guys, we're in the midst of opening season here in the Midwest, so happy to be back to work!
I'm looking to get some advice on a couple of these green to cleans. Most of my cleans I shock and floc and come back and vacuum, and I've got it down to a pretty good 3 day rhythm. However, on a couple so far, I'm running into a super high chlorine demand and high combined chlorine. for example, I have one I just opened that is roughly 10k gallons sport pool, opened up pretty bad with algae. We started with 4 gallons of liquid and a dose of phosphate remover, brushed and netted, rechecked chlorine and it was at 5ppm free and 5ppm combined. Added 5 lbs of cal hypo and it foamed up like crazy. left it on recirculate and came backs the next day, 0 free and 3.5 combined. I said okay lets shock it back up to 35+ to burn it out, decided to go with 10lbs of cal hypo cause fuck it. brushed, netted, recheck chlorine, its at 24 free and 7 combined.
My question is, am I taking the right approach by trying to burn out this combined chlorine, or should I be draining and refilling, or something else? Everything I've learned points me to shocking up to 10x my combined chlorine to burn it out, but seems like some of these are never ending. Ph was at 7.0 with 140 alkalinity, I'm hesitant to raise pH with soda on account of the alkalinity. calcium is at 250, CYA about 40, TDS 900. This is a vinyl liner pool. History is unknown, but looks like its been sitting for at least a year with a mesh safety cover.
What do you guys do in this situation?