We have been using a 1G poland spring water jug (or any jug). Cut away the bottom of it and turn it upside down so it looks vaguely like a funnel, drill a couple of holes in the cap to let out the water, stuff some pillow floss down near the bottom to catch loose particles, and pile on several inches of peat moss. It's a crude filter, and we just directly pour water through it into a bucket/tank. It's very fast and takes down the pH of our city water from ~9 to ~6. Have to replace the peat every 20 or so gallons of water you pour through, but it's pretty easy.