Abstract: A hot water plumbing system comprising a water heater, a delivery location, a delivery line delivering water from said heater to said delivery location, a riser located adjacent said delivery location and extending upward above the level of said heater, and a return line connected adjacent the upper end of said riser and inclined so as to extend gradually downward to an input located adjacent the bottom of said heater to provide a continuous flow of hot water within the system, which ensures immediate and constant delivery of hot water to the delivery location and prevents accumulation of sediment within the system and, hence, minimizes installation and maintenance costs and significantly reduces the amount of wasted water. The system particularly employs a vacuum accelerator, which can be used to increase system vacuum and which causes rapid start-up or priming of the system.