My wiki on how I built my pool automation system.
See tabs at the top of this page for information of various parts of my system.
I use Wemos mini D1 pro type ESP boards to control the relays that control the system. They talk MQTT to a raspberry pi running Home Assistant and Node Red that are really the brains of the system.
Spa Volume notes
7 feet diameter = 84 " = 42" radius
2-3 feet depth use 2.5" depth = 30"
720 gal based on 42"r x 30" d
.7 oz cal hypo to add 5ppm cl
.5 oz vol cal hypo to add 4ppm cl
4 oz vol stab to add 40 ppm
Pool Volume
20,000 gal