What is a pool filter, exactly? Is it the "basket thing" on the side of the pool, the little cleaner that runs around the bottom, or the giant canister at the equipment pad that just seems to take up space?

Well, since third time's the charm, we're going to go with #3.

Oftentimes, pool equipment is treated like a car - getting as much use as possible, until just barely reaching the threshold of catastrophe, and finally, begrudgingly being dealt with at the last minute.