Our water is treated with chloramine; campden tablets work very well.
There are several problems that we have seen with garden hoses hooked up to standard filter housings. Sanitary issues, flow rates higher than the filter cartridge can handle, and bleed by. The proper flow is very important for good contact time with any filter media. As for the sanitary issues regarding GAC and or carbon block if not handled properly bacteria could be an issue. We always wear gloves when working with filters of any type.We also clean and sanitize the filter housings. Just these small steps can make a big difference.
I was referring more to the canister's efficiency in stripping out chloramine. I'm not worried about the rest.