Turn a measured pump output into a schedule, and check what the tubing drift is costing you.
Recalibrate every couple of months. Peristaltic tubing flattens where the rollers press it, and output falls off gradually enough that nobody notices until alkalinity has been drifting for weeks. Replace the tubing yearly.
rate = 52.0 mL ÷ 60.0 s = 0.8667 mL/s · run time = 1.667 mL ÷ 0.8667 = 1.92 s
Peristaltic pumps are calibrated by measurement, not by their rating. Run the pump into a measuring cylinder for a known time, and divide.
Use at least 50 mL for the calibration run. Measuring 5 mL in a kitchen jug carries perhaps ten percent error, and that error propagates straight into every dose for months.
Output drops over time. The tubing flattens where the rollers compress it, and the pump quietly delivers less than it reports. Alkalinity then drifts down slowly, which reads like rising demand and gets treated as one. Recalibrate every two months and replace tubing yearly.
Head height changes output on cheaper pumps. Calibrate with the tubing routed exactly as it will run, not coiled on the bench.
More doses of less each is better. A litre of two part split across 24 hourly doses barely moves alkalinity per dose. The same litre in one shot swings it half a dKH and then lets it fall all day.
Separate calcium and alkalinity in time. Dosing both into the same spot at the same minute precipitates calcium carbonate, which is visible as a white crust on the dosing line outlet and as parameters that will not hold.
Put the dosing lines at opposite ends of the sump, in high flow, and offset the schedules by at least fifteen minutes.