> Partial filtering

It seems like we're mixing up terms here and miscommunicating. I thought we were talking about actually replacing the water here (as in, down the drain, fresh water from the tap), not just filtering as in recycling water through filtration systems. The total volume of the water should go through filters every few hours. I'm 100% not for the idea of only "partial filtering".

> To me it feels like it falls in the "expected" category somewhere that is dealing with hundreds of swimmers including small children every day.

Nah, that is definitely not normal to have to completely replace the water multiple times in a year because of water contamination events happening. The water can usually be sanitized. It might require a day's worth of hyperchloronation, but not often an entire drain and fill. That will happen often, probably several times a year. Usually only if your CYA is too high will it require you to actually drain a significant volume of water, which I agreed was one of the reasons to at least do a partial drain and really only applies to outdoor pools. Doing a hyperchloronation will likely increase your TDS, which won't go down until you drain those contaminates. But usually you can get those numbers back in an acceptable range without having to drain and fill the whole pool.

If the pool was properly maintained, what state do you expect the water to be in after a year without a total drain and fill? Do you have experience actually maintaining a pool?