The simple and inexpensive filter herewith described is designed to purify the rain-water flowing from the roof, and conduct it to a cistern. The water from the roof flows through a pipe from a leader into a compartment in the lower part of the tank. The first water, which has washed the roof, is allowed to flow through the faucet and go to waste. When the water is comparatively clear the faucet is closed, when the water flows upward through a false bottom supporting the filter proper, which is made smaller at its lower portion than at its top, and which snugly fits the tank, a packing making it water-tight against the sides to compel the water to pass through the perforated sides and bottom into the interior, which is filled with sand, charcoal or some other suitable material. The water then flows through the pipe in the upper compartment to a cistern or reservoir. It is evident that by admitting water at the bottom and causing it to be purified as it rises through the filter, all leaves or dirt of any kind will be held back by the perforated false bottom, and, after the rain has ceased, may be discharged through the faucet. It is thus impossible for any decomposable matter to find its way into the cistern. This invention has been patented by Mr. Benjamin Ligget, of Arizona.