We are interested in wasting as little water as possible and to that end, we designed a structured plumbing system that allows for the hot water to circulate within a loop system of pipes to deliver hot water at the faucets when needed. The only line that will not be part of this system is the kitchen run. That water needs to be very hot for the dishwasher and is close to the utility room so it will be plumbed separately.
The pipes with the caps hold the 3/4″ PEX. The pipe continues to the back bathroom where the hot loops back to the source.
LEED gives points for a structured plumbing system. Basically it does not matter how long the loop for the hot water plumbing is as long as each branch is under a certain number of feet. So having a long loop with several connections will provide the structured system. UPDATE: WRONG! LEED requires a total loop length of 40 feet with an additional 2x the ceiling height for 2 story homes. This means that although Gary Klein’s designs don’t limit the length of the loop, LEED does. At maximum we could count the upstairs as a second story and the highest ceiling at 12′ which would give us a total loop length allowable of 84′. Since the loop travels just about the length of the house and back, we probably have more like 130′ of loop length. No structured plumbing points for us. That is why LEED can be so infuriating. All or nothing in many instances.
For information about the design, we used Internet publications from Gary Klein of California State University. He recommends wasting no more than 1 cup of water to get hot water to the fixture. That translates into about 5 ft. of pipe from the trunk line. LEED is a bit more generous with pipe length to qualify for structured plumbing points allowing 24 oz. from the structured plumbing loop, or about 20 ft. of pipe to serve the fixtures.
We will be close to the Klein recommendation because most of the “twig” runs from the trunk pipes are very close to the fixtures. The only extensions are for the bathroom sinks and that is less than 10 ft. of pipe from the trunk to the fixtures. The trunk lines run from the water source in the utility room to each fixture and the hot returns from the furthest fixtures back to the utility room so that a circulation pump can be installed to move the hot water through the trunk before use instead of moving the water down the drain until the water gets hot. There must be an aquastat sensor added to the system and some means of controlling the system from the points of use. Taco makes a D’Mand system for under a distant sink that runs the hot water back down the cold pipes. It might be modified to fit this system only hooking the return pipe back into the trunk run. The important part is that there is a control system that can be installed for manual or wireless operation.
The loop runs from the water supply in the utility room to each water use “island”. In this photo, there are three, the garage utility sink, the outdoor water spigot supply, and the bar sink. The pipe continues to the master bath from this point.