NIST Plumbing Research Act of 2021 This bill directs the National Institute of Standards and Technology (NIST), in collaboration with the Environmental Protection Agency and the Department of Energy, to establish or designate a laboratory to conduct research on premise plumbing in relation to water safety, security, efficiency, sustainability, and resilience; conduct an organizational review of all research and other activities related to premise plumbing conducted by federal entities; and appoint one or more officers or employees of NIST to liaise with nonfederal entities that are conducting research or other activities related to premise plumbing. The bill defines premise plumbing as the water distribution system within the property lines of a property, including all buildings and permanent structures on such property. This term also includes building supply and distribution pipes, fixtures, fittings, water heaters, water-treating and water-using equipment; and all respective joints, connections, devices, and appurtenances.