Here is your place to shop for your filters. This gentlemen knows his stuff and is very helpful if you give him a call. We get our filters from him. We have one on the water coming into the tank and one at the kitchen faucet to remove taste.
We boondocked a lot and got our water from various sources. We fill the tank and drink and cook from the tank water. With filters we had no concerns.
Hauling water get old and buying it...some comes from not so good sources anyway. All they do is filter it, as you can easily do.
http://www.rvwaterfilterstore.com/