I took your approach and let it go at the end of the season.

So far, I'm on day 3 using about 18 gallons. I'm only losing about 3ppm overnight, but the daytime loss is huge.

I have filter cartridges, so it's very difficult to keep up good pump pressure after about 20 minutes.

A ton of vaccuming along with it. I'm hoping to be done by the weekend, we'll see...