Project
Pool chemistry
A dosing calculator for a stubborn residential pool — the small, exacting kind of problem I can’t leave alone.
The problem
Some pools are chemically easy. This one isn’t: the source water is chronically hard, which pushes the whole system around and makes the usual rules of thumb wrong in ways that stay wrong. I got tired of doing the arithmetic by hand and second-guessing the order of operations, so I built the tool that does it properly.
How it works
You enter the current readings and it returns the doses in the right order — and order matters, because the wrong sequence sends pH one way while you’re fixing alkalinity the other. It knows the treatment precedence, the interactions (acid drops alkalinity; aeration lifts pH), and the safe limits, and it explains why it’s recommending what it is.
It also estimates where the chemistry has drifted since the last test — chlorine decay, pH off-gassing, even rainfall, which it pulls from the nearest weather station to dilute the numbers accordingly. The goal is that the number it gives you is the number you’d get if you re-tested right now.
Why bother
Small stakes — a pool either stays clear or turns green — but that’s exactly the appeal: exacting feedback on a bounded problem, the same thing I like about everything else here. It’s a personal tool, calibrated to one particular body of difficult water, but the chemistry underneath it is general.