Top photo shows an installed, 15 gallon, muriatic acid feeder. The electronic controller checks the pH sensor every 30 seconds during the filtration cycle. If the water is above 7.1 pH, the acid pump is turned on for 30 seconds.

The lower right photo shows the dial with locking bar that adjusts the length of the piston stroke to affect total alkalinity (TA). (Longer strokes will lower TA more than shorter strokes.)