I tried the reply and noticed your question was a bit different from what I thought it was.

Things to look at for are:
- Pumprate or gravity fed (with the amount of water involved you need to be efficient in time and energy).
- Carbon filter to remove chemicals, filters with replaceable carbon granulate can be a nice feature if you want to make sure you are not using ‘used’ carbon, when filtering possible contaminated water.
- I prefer ceramic filters, because they can be cleaned. Some prefer the fiberglass versions, because they have a higher flowrate.
- Use a good prefilter to get all the debris out first, gravity fed is best.
- Make sure you have enough water containers to shuttle all the water around.

More on the filters them selfs: http://www.equipped.org/watrfood.htm#WaterFilters