The interesting thing is that every time we went, it appears that the Mickey and Goofy pools were drained and refilled at least once for one reason or another. One time it was because someone got sick in the pool. Everyone had to get out and they roped it off. It was drained then cleaned. It was fully refilled by the next morning.
Sure, it was somewhat of an inconvenience, but they sure take hygiene seriously, which I view as a good thing.