Hi,
We probably have very similar weather conditions so this could be very diagnostic for me.
I have the water checked about every 3 months by the pool shop and they say it's fine. Evidently not, I also thought that I was using excessive amount of salt. Just yesterday I chucked in 100kg (start of summer), swung the salt test switch over this morning and it shows that I still nedd salt?
You might have the self cleaning unit (which requires cleaning at about the frequency you indicate). Mine is the el cheapo (I am desperately looking for a circuit for the self cleaning model).
We need to backwash weekly due to the high dust content in and about Johannesburg, especially in winter. Don't have overflow but can have the pool fill to the brim during a thunderstorm.
Although I have a borehole we do not use this to fill the pool and we do use sulphuric acid.
Mu missus maintains the pool and I don't think that she adds cyanuric acid, if so this will allow the escape of the chlorine through evaporation?
Any thought
Cheers
AndrewPS: She is off shopping now, gonna ask her to get the water tested.