For the trip you mention, I wouldn't bring a filter. I'd bring water treatment tabs or liquid. I don't like the iodine tablets, there are other types nowadays. If you do bring iodine tabs, vitamin C crystals help with the taste.

As other folks mention, you should be able to fill up along the way.

-I'd figure you might want to treat water twice (at most) for that trip. Say-if you get low between stores and fill up at a stream, which will be near the road, and PERHAPS contaminated. Or perhaps at a campground-and your not too kean on how close the water pump is to the leaching field.

Having some type of water treatment system (filter or chemical) will give you more options, especially if you want to do any hiking.