Hi Smile;

Just commenting here on the expected vs actual CYA levels. There's a good chance your pool is not 36,000 gallons. It's visible on Google Maps, and looks like standard rectangle liner pool with 4' radius corners, 3.5' WATER depth in the shallow end and maybe a 9' hopper. Keep in mind, builders and liner makers tend to quote gallons at overflow, not at operating depth!

I ran these calculations:

Top 3.5' of entire pool:
20 * 40 * 3.5 * 7.48 = 20,944 gal (this overstates gallons, due to rounded corners and beveled wall to floor transitions)

Hopper only, going from 3.5 water depth to 8.5' water depth - avg depth = 1/2 of difference (again, an over-estimate, but I'm not going to do a more accurate calculation yet.)
20 * 25 * 2.5 * 7.48 = 9,350

So, your likely actual water volume may be closer to 30,000 gallons, than to 36,000. Even a 10' nominal hopper (9.5 water depth) would only take you to 31,000 gallons.