Hi, I'm getting TA = 148 at the deep end & TA = 90 at the shallow end. The pool is an outside, in ground, typical liner pool with inward sloping sides to a 7' 'hopper' shaped deep end L=30' W=15' (about 15,000 imp. gallons) The rest of the equipment consists of multi-port valve sand filter, gas heated to 28c in season & 3/4hp pump, a 'FROG' mineral cycler kept topped up with 2 stabilised 5 way multi-functional CL tablets. Flow rate into the pool from both inlets appears & feels strong & pretty well bounces off the far side, PSI is fine, opening/closing the skimmer & main drain valves doesn't show up any suction problems. FC = 2.7: PH = 7.6: CYA = 40 & those readings are pretty consistent over the length of the pool. The pool is 4 years old, fairly lightly used most of the time but I regularly manually vacuum & backwash & never had cloudy or green water problems. I don't use additional algaecide. It stay crystal & sparkly & so working on the principle that "if ain't broke don't fix it" apart from the start & end of the season (when I it get up to 15ppm with liquid CL)... I don't shock it. I use Fi-Clor products (dry acid, soda ash) to make any adjustments, rarely need to but I AM familiarised with the different dosage techniques. (dribble, slug still water... Iv'e tried them all!!) I keep the water level about a third of way up the skimmer but occasionally let it drop & then top up with fresh tap water to keep the CYA from the tablets under control. I normally circulate overnight (9 hours) with solar cover over but have tried 24 hours 'open' (several times!) & I dunno what else to think of! I'm stood standing scratching my head!! My tap water TA is high at 138 but I allow for that to settle & then try to treat it if I have to but despite several days of recycling even 'normal' TA readings at the ends of the pool are so dramatically different. I'd be grateful for ANY opinions, comments or suggestions of what to try next. Thanks, Don.