Liquid pumping system with pressure relief mechanism

This disclosure relates to a system for pumping a liquid from a storage tank, through a pipe and out of a valve of a liquid dispenser. The apparatus comprises a manifold housing having a main flow passage formed therein, a check valve mounted in said main flow passage and enabling liquid to flow from the storage tank to the liquid dispenser, and a manually-operated pressure relief mechanism around the check valve. The mechanism comprises a bypass flow passage formed in the housing in parallel with the check valve, and a stopper which normally closes the bypass flow passage. To relieve the liquid pressure, the stopper is manually moved to a relief position where it is removed from the bypass flow passage, thereby enabling the liquid to flow around the check valve. To resume normal operation, the stopper is returned to its normal position where it blocks the bypass flow passage. The stopper is movably mounted in a bore in the housing, and the bore extends to an opening at the exterior surface of the housing. A seal is provided between the stopper and the wall of the bore, to prevent the liquid and vapor from entering the environment.