Abstract: A liquid purification system is disclosed. In this system water is pumped into a filter cartridge. A reverse osmosis filter membrane in the filter cartridge removes impurities from the water, but not all of the water passes through the membrane. Water passing through the membrane exits the filter cartridge through a first outlet port, and is sent to a storage tank. Water not passing through the filter membrane exits the filter cartridge through a second outlet port. This water then passes through a pressure relief valve. The pressure relief valve can be adjusted to vary the water pressure and flow rates in the system. Some of the water exiting the pressure relief valve passes through a flow restrictor valve and then to drain. The flow restrictor maintains a constant flow rate at variable pressures. In this system, the flow restrictor is operable to maintain the same flow rate through it to drain and through the first filter outlet port.

Abstract: An improved multi-port connection device (10) adapted to receive prior art membrane and filter canisters (12) and to make connections between plural connection devices more convenient and versatile, comprising a plurality of flow ports (43,45,47) which are all at a common level, two of which communicate through apertures (52,54) in a barrier wall (55) forming a female connector with input and output flow paths (18,16) in the canister male connector, said apertures (52,54) being positioned in the barrier wall (55) on separate sides of an O-ring seal at locations communicating with the input and output flow paths (18,16).

Abstract: A flow restrictor that is intended primarily for use in a reverse osmosis water purification system of the type having a reverse osmosis membrane housing receiving feed water to be purified and generating purified water at a first outlet and waste water at a second outlet. The flow restrictor of the invention comprises a selected length of elongated, doubly-extruded tubing having an inner, low-friction tube and an outer, higher-friction tube. The outer tube is coaxial with the inner tube and has an inner surface which is substantially contiguous with the outer surface of the inner tube. The diameter of the inner tube and the length of the tubing are selected for precisely limiting flow of water therethrough.