Pool Automation Chemistry ... Impact of sun/weather variables on chlorine levels

[Stephenmayer]

Hi All!

I'm wondering about putting together a chlorine pump system for my pool ... and after reading some of the posts related to how difficult it is to calibrate and use an electronic sensor (orp probe, for example) to measure chlorine ... So I'm thinking of building something and using other information to predict how much chlorine the pool will need based on weather data. (see: DIY with Liquid Chlorine, ORP Probe, Arduino)

I have a weather station in my yard. I was thinking about writing a computer program that calculates how much chlorine to add to the pool each day based on the relative amount of sun the pool receives during daylight hours (using a solar radiation sensor). I've noticed that my pool uses more chlorine on a sunny day than it does on a cloudy day.

I will, of course, closely monitor and calibrate the system based on observations. I don't expect this system to be fully automated, but instead be able to perhaps do a reasonable job of maintaining the pool if I have to leave for a few days on vacation. I'm thinking about something like this:

if (100% sun all day ... solar index 44783.98) {
-- add amount of chlorine that the pool generally loses on sunny days (I generally lose 3ppm on sunny days ... so add 3ppm)
}

if (cloudy day ... solar index 11434.3) {
-- assume chlorine levels dropped 2ppm to 5ppm ... add 2ppm
}

if (partially cloudy ... solar index 25000) {
-- add 2.5ppm
}

Note: solar index obtained by adding up all of the solar readings throughout the day, measured every 5 minutes.

I'm also wondering if there are other weather-based variables that I could also also use, and what impact they have. Should this formula also take air temperature or pool water temperature into account? Should it add more chlorine if it rained during the day?

Thanks!
Stephen

 

[Philo]

Sound like you got a good project underway.

Quantity and quality of swimmers will impact chlorine.

 

[Organizer]

I can pass along my 2 years of experience with my homebrew CL injection system, utilizing a fixed rate Stenner pump controlled by a timer. During the swimming season (June- October here in NE Florida) my CL remains between 4.5 and 6.0 (with CYA at 35) without any adjustments to the timer. Only exception was a hurricane in 2016. I test my pool water daily. Our bather load is pretty constant. This leads me to conclude that for my pool, an automated system would be overkill.
That's only my pool, so I wouldn't make any decision based on my thoughts alone. There are many others on the forum with CL injection. Perhaps some of them will share their experiences.
All that said, it sound like a fun project. I look forward to hearing more.

 

[Topher55]

My stenner is rock solid I can go several weeks and stay +\- 1 ppm FC. I do manually ramp up in spring and ramp back down in the fall. I will also manually dose before and after a big party but I don't think that can be avoided. Maybe a program could help with the seasonal ramping.

That being said it sounds like a cool project!!

The only thing I have ever wished for is a timer that would take x minutes off the next run so when I'm 1ppm high due to 5 cloudy days in a row I can take 30 mins off the next injection then resume the normal schedule. My current Christmas light timer from Lowe's is pretty limited...