I have a rural water supply and a few year ago I purchased a small pool for the kids. I added chlorine like the instructions said and my kids swim wear bleached so I checked my chlorine from the tap 4 ppm. RO only takes out 2 ppm per Kent Marine. How many times are we overdosed from the water supply companies? Better to be safe then sorry. Only 1 or 2 companies make chloromine remover. The others just break it up? I use the Chloromine Blasters with a double canister to help with this problem and still add drops. I haven't lost a fish since I started this practice and also not using a garden hose. As far as DI units 100 to 200 gals is all they last on my water system.