LB pumps are diaphragm pumps with a coupling rod driven by a gear box speed reducer. The flow generated by the movement of the diaphragm is controlled by check valve at the suction and delivery. As the diaphragm rises away from the bottom of the casing it produces a vacuum which draws the liquid into the casing through the suction valve. When the diaphragm is on the downstroke, the liquid is expelled through the delivery valve. LB pumps are reciprocating positive displacement pumps. The delivery line must therefore have an adequate diameter and be free to discharge the liquid being pumped to avoid pressure build up which can damage the diaphragm or the drive mechanism. The pump should be connected to pipework using sections of flexible hose to avoid transmitting the pulsations of the pump to the rest of the system.