A pressure-reducing flow regulator for use between a pressurized source and a pump inlet uses dual pistons to reduce the pressure at the pump inlet. Pressure reduction is achieved due to the ratio between the sum of the areas of the two pistons and the area of the inlet. When used in a compressed air foam system, this pressure reducer serves to increase the volume of air available at the desired pump pressure. In one embodiment, a flow of liquid is allowed through a central tube between the two pistons. In another embodiment, the central tube is sealed and a low-pressure bypass allows for flow between the outlet chamber and pressure chamber.

A bicycle air pump includes an air cylinder; a joining member on the cylinder and including upper, intermediate and lower chambers, and a passageway communicating the cylinder with the lower chamber and a relief valve; an activation assembly on the joining member and including a hollow spring-loaded stem in both the intermediate chamber and the lower chamber, an end seal, a cap on the upper chamber, a push rod through the cap to urge against the seal and having an axial hole and a lateral hole communicating with the axial hole, a knob secured to the push rod and the cap, and an outlet; a pressure gauge on the joining member and communicating with the passageway; an inlet assembly secured to bottom of the cylinder and including a check valve; and a blocking member secured to bottom of the stem for blocking the passageway when in an inoperative position.

A first stage pressure regulator is provided. A valve body has an inlet and an outlet that define a pressure chamber therebetween. The valve body defines a pressure compensation chamber having an opening fluidly communicating the pressure compensation chamber with the surrounding water. The first stage pressure regulator comprises an inlet tubular union removably received into the inlet. A removable high pressure orifice body defines an orifice therethrough. The orifice body is carried by the valve body proximate the inlet. A valve seat is within the valve body.

A flow direction restriction valve mechanism unit includes a pressure decreasing valve assembly that is located to be freely advance or retract in a combination valve cassette attached to an in-outlet secondary side flow path formed on the side of an outlet with respect to an intermediate transmission member in a flow path, and retracts by a pressure of gas; a first coil spring urging the pressure decreasing valve assembly in a retracting direction; a check valve that is located to be freely advance or retract with respect to the pressure decreasing valve assembly, and retracts by a pressure of the gas; and a second coil spring urging the check valve in an advancing direction. A gas induction passage H is formed in which the gas flows and acts on the pressure decreasing valve assembly such that the pressure decreasing valve assembly moves in the advancing direction.