Abstract: A pressure relief valve integrally formed with a section of conduit in a closed system for pumping cementitious material eliminates any dead space in the system within which the cementitious material may flow and set, and thus avoids system disassembly for cleaning following use and the possible replacement of clogged system components. The pressure relief valve includes a hollow cylindrical housing disposed on a conduit. First and second elongated linear slots are aligned with the cylindrical housing's longitudinal axis and are disposed in opposed portions of housing, with one slot in flow communication with the conduit. A cylindrical drum having a third elongated linear slot disposed within the cylindrical housing is freely rotatable therein. A handle attached to one end of the drum allows for manual rotation of the drum for aligning the three slots permitting the discharge of cementitious material and release of pressure in the system.