The Type 567 plastic butterfly valve from GF Piping, Tustin, Calif. (gfpiping.com), works with pressures up to 150 psi.
Its double eccentric design lets engineers use different sealing methods for the exterior and passage seals. The design prevents the valve from touching the inside of the passage, so opening and closing torque is said to be half that of centric-designed valves. The outside uses double O-rings, while in the valve's passage, a profile seal maintains valve integrity. And all parts of the valve that touch the flowing media are the same material, either PVC, CPVC, PP-H or PVDF. The housing is fiber-reinforced PP-H.