A foam pump including a pump housing with a liquid chamber in fluid communication with a foamable liquid filled container and an air chamber in fluid communication with a high pressure air source through an air inlet. The foam pump also includes a dispensing tube having a wiper seal post with a closed distal end positioned within the pump housing, and an outlet tube with an open distal end positioned outside the pump housing. The wiper seal post includes at least one inlet hole in fluid communication with the liquid chamber, and a check valve near the second open end. The foam pump further includes at least one foam screen in the open end of the outlet tube, a wiper seal slidably positioned around the wiper seal post and in sealing contact with the pump housing and the wiper seal post, and a spring bias to bias the wiper seal in an unactuated position. The wiper seal forms a movable barrier between the liquid chamber and the air chamber and is adapted to slide axially along the wiper seal post past the inlet hole when actuated by high pressure air, thereby allowing the high pressure air to enter the dispenser tube and cause mixing of said air and foamable liquid within the dispensing tube. The mixture is then expelled through the check valve and the foam screen.