Test results on new pool in Tucson

It may be that some of your CYA biodegraded. That is pretty common and we see it a lot of times in the spring when people open their pools. If it biodegrades, it can leave ammonia as a byproduct which causes a huge chlorine demand to get rid of it. I have a feeling that is what is going on in your pool. Or, you may have some other type of organic in the water that you cannot see that is causing the demand. Sometimes a pool can be on the verge of an algae bloom without having any visible signs and you go through a lot of chlorine. I highly doubt that having hard water would have any effect on chlorine use.

I don't know of anyone here who has heard of a connection between hard water and chlorine neutralization.
Other than organic matter that the chlorine metabolizes, the only chlorine neutralizers I know of are solar UV rays and Sodium Thiosulfate (R-0007 in the Taylor reagent chemicals).

Last night, tested at 6 pm, got 13 ppm, added 2 gallons. Got a little rain last night, retest at 7 am, 12 ppm. Added my last gallon. Back to store for more. That's 11 gallons in 3 days.

Ok, new twist. Given your thoughts that there is still something organic going on. I reconsidered something. At different degrees, there has rather consistently been a loose, brown, fine debris that accumulates on the step down shallow area surrounding the pool, and somewhat in the corners.i thought this was dirt, as we have planters, etc around the pool that may leak into the pool during storms I suppose. I had been brushing daily last month, but had gotten away from that as the chlorine upkeep became paramount. Is this algae/dead algae?

If you were here in the NE we'd be saying pollen--it's allergy season here.

Ok, so I just had a revelation, I think. I believe I mentioned that I had a 500 gallon spa attached to the pool? Well, it's attached but only with overflow into the pool. I never actually tested the spa water, thinking it was all the same, and it would splash it with bleach or shock, but not test it. We'll I tested it. Ph unmeasurable high, like probably 9, and no detectable FCC even after a gallon of Clorox. I think it has been bleeding into the pool and acting as a feeder of algae, and I was just band aiding it instead of treating the source. So I hit it with acid and more bleach and will retest often. Jeez.

Regardless, it's not the pollen that is causing your chlorine demand. Get FC to 25 and try your very best to keep it there without too much of a drop. 11 jugs doesn't seem like that much to tell you the truth. Keep the faith!

Okay, cross-post. Let us know results of spa testing. Spas can be nasty creatures. My apologies for not remembering the spa over-flow. Why do installers do that? Yuck.

Got the cl up to 25 in the spa, but ph still high, added 2 more cups of acid. Plus we are supposed to get major monsoon rains next few days. I am going to need more testing supplies, that's for sure. Got the too kit, but not ready for it at all yet.

*OTO kit