A fully-draining check valve with a mushroom assembly having a tapered back edge and a drain line disposed with the lower rim of the drain line below the tapered back edge to ensure no fluid becomes trapped in the check valve when not in use. Additionally, a fully-draining diaphragm pump is disclosed having a drain line configured to drain the lowest point of a product chamber to ensure no fluid becomes trapped in the diaphragm pump when not in use. A method of cleaning a fully-draining diaphragm pump and fully-draining check valve assembly is further disclosed comprising inducing turbulent flow of water, wash solution, and/or sanitizer through the assembly and opening ball valves the drain lines of the fully-draining check valves to vent the assembly.