GLACIER FRESH Garden Hose Filter Pre-Filter for Pool & Spa 1-Pack

Every water change starts with whatever the hose delivers. On city water that is usually fine as it comes. On a well, or through old pipes, it can mean sediment and a smell before anyone has been in the tub. This blue cartridge screws between the tap and the hose, or onto the hose end, and passes the fill through coconut-shell activated carbon. The maker says it reduces sediment, chlorine and odors and rates it for up to 8,000 gal (30,283 L).

The chlorine part cuts both ways. Less chlorine means less smell, and it also means the tub starts without the small dose of sanitizer that city water carries. The NSF mark on the label is a materials certification, and the listing gives no micron rating, so treat it as a first rough pass rather than a guarantee.

Tip: Let the water run through it for 30 seconds before you point the hose into the tub, as the listing advises.