I've been a bad person lately--haven't been watching my pool much--just dumping in a gallon of 12.5% every couple of days and nothing else.

Not too smart.

So....Today I got out the PS-233 (For those who are new, it's essentially the same as the K-2006) and ran everything except Calcium Hardness.

I have a 20,000 gallon vinyl FantaSea A/G that's 16x40 with a 5.5' deep end, and a 200# sand filter and Hayward 2spd Superpump (1hp). Pump runs (always on low) from 7am to 8pm and from 11pm to 2am

My numbers came up:
T: 83 deg F
FC: 4.5
CC: 0
TC: 4.5
pH: 7.6
TA: 90
CYA: 40

Talk about dumb luck! I would NOT recommend this course of action.

However, I've noticed that if my pool is well-balanced and I dump in 1 gallon of 6% every 2 days it stays VERY stable. I haven't had to backwash for many weeks, either.

When we go away, I simply have my pool care-taker (usually my FIL) follow that routine of 1 gallon every other day.