Pool Heater
Trying to get more warm-water days out of the pool. Pumps, plumbing, temperature sensors, and Home Assistant are involved.
Warmer water, please
This is a DIY pool-heating project with a straightforward goal: make the pool more comfortable to use. Getting there involves plumbing, moving water, measuring temperatures, and deciding when the equipment should run.
The pieces
Pumps and plumbing handle the water. Temperature sensors and Home Assistant handle the monitoring and automation. The interesting part is getting those pieces to work together outside, where the weather and water temperature keep changing.
How it works
A pump moves pool water through an on-demand water heater, which turns on whenever water flows. An outdoor plug connected to Home Assistant switches the pump. During heating it runs 25 minutes on and 5 minutes off, and temperature sensors tell it when to start and stop.
There are two set points: a maintenance temperature of 78°F, and a “ready mode” of 85°F for when the pool is about to be used.
Finished
I was happy with the result, and it works as intended. The combination of the Home Assistant plug and the on-demand heater did exactly what I wanted, so this project is complete.
The sensor
Building my own temperature sensor with an ESP32 was incredibly fun. The one thing I wasn’t happy with was battery life, which was only about five days. If I had kept going, improving that would be the first thing I tried.
Project timeline
Along the way
- Latest update
Done, and it works
I’m calling the pool heater complete. I’m happy with how it turned out. While heating, the pump runs 25 minutes on and 5 minutes off, and there are two temperature set points — a maintenance mode at 78°F and a “ready mode” at 85°F for when I want to swim. A Home Assistant-connected outdoor plug switches the pump, and the on-demand water heater fires whenever water flows, so the two work together perfectly. Building my own ESP32 temperature sensor was incredibly fun, though I wasn’t happy with the roughly five days of battery life. If I had kept going, that is what I would have tackled next.
How I put it together
I wrote up the build, from choosing a tankless gas heater over riskier options to the Home Assistant automation and the temperature sensors outside by the pool.
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