Alkalinity is 80, calcium hardness 220, TDS 1000, Phosphates 0, CYA 40. Chlorine stable at 2+ppm. I use 3" trichlor tabs but still am constantly adding acid, I can take the PH to 7.4 and a day later it is 7.8 or 8.0 - I have 3 pool supply houses here (Leslies and 2 small independents) and none of them have a clue why. About two months ago, due to high Calcium, high TDS and high CYA. I drained between 1/3 and 1/2 of the pool. My tiles were badly scaled so before draining, I added 2 quarts of BIO-DEX Protectall Supreme, filled the pool completely and ran the filter for 3 days straight (at their suggestion). This was supposed to soften/loosen the scale which it completely failed to do. I hand scraped the scale with more razor blades than I care to remember, then ran the pump for another 2 days to vacuum up any scale I could. I then drained and refilled the pool, re-balanced the water as per the "experts" advice and all was fine for over a month. This PH thing is 3 weeks old now and I have done nothing but add acid and tabs.

Any ideas would be greatly appreciated.

I'm not sure if my filling in of pool stats took, so here goes
39x19 feet shallow 3 deep 9
white plaster
25-30,000 gallons
hayward 60 sq ft DE filter
1 HP Whisper-Flow Pump
10 hrs/day
Kreepy with dedicated suction port
very very low swimmer load, very few leaves, etc