With a typical cartridge filter system you have to let most of the anti-freeze go into the pool, which isn't a problem. There should be a garden hose style valve, used for draining, that will let water out, but it doesn't get a high enough percentage of the water going be to make a significant difference. As long as you used pool anti-freeze this isn't a problem. Pool anti-freeze is the same stuff that they use in the drinking water tanks in RVs, ie suitable for human consumption.