This Floor Plan Plumbing Layout Plan clearly shows the location of the fixtures, pipes, and valves. Plan of the Floor When designing a house or building plan, the Plumbing Layout Plan is critical. The plumbing system of a home is a complex network of water supply pipes, drainpipes, vent pipes, etc. Because plumbing is a complicated system that is one of the most expensive to repair or install in a home, it is important to understand how it works. The delivery and distribution equipment is a network of water pipes, fittings, service valves, and faucets. Plastic, copper, or galvanized iron are common materials for these pipes and fittings.