We gave some very careful thought to the plumbing in the Kalamazoo ZEHR home, as we do with any new home we build. Every home we build incorporates water-saving fixtures rated by the EPA WaterSense label. These fixtures use less than typical plumbing fixtures, and can reduce the water usage (and therefore water costs) of the homeowners, as well as have obvious environmental benefits through the use of less clean water. From our experiences these fixtures perform as well as standard fixtures and don’t typically cost any more to buy. The image below is found on WaterSense labeled products:
Aside from the efficient fixtures, we are also trying to design the plumbing supply lines in the home to be as efficient as well. In most homes, water lines are typically run as 3/4 inch mains, which then reduce before the fixtures to 1/2 inch pipe. These pipes are WAY over sized for the amount of water required by almost every fixture in a home. Most shutoff valves under a sink or toilet have an opening of less than 3/8 of an inch, so why make the pipes any bigger?
Also, locations where the water is used, such as kitchen, baths, and laundry, can be spread all over the home, making long runs of pipe to each room. It is amazing how much water pipes can hold. A 50 foot long run of 1/2 inch pipe holds about 1/2 gallon of water, while a 3/4 inch pipe holds over double that at 1.15 gallons. With all of the long runs, twists, and turns in a standard plumbing system, it is easy to have 50′ of pipe or more to many fixtures. So reducing the size of pipes carrying water can reduce the amount of water standing in the lines.
So, why does this matter?
All of this comes into play when using hot water. When you turn on a faucet to wash your hands or wash dishes, you often have to wait from several seconds to sometime more than a minute before the cold water sitting in the pipes is pushed out and hot water arrives. We’ve all experienced this at some point. During this time, anywhere from several cups to a few gallons of nice, clean, potable water goes right down the drain. This may not seem much, but added up many hundreds of times over a year can lead to thousands of gallons of wasted water. This is both a waste of water and money. Here in Michigan we are extraordinarily blessed to be surrounded by fresh water, but water still takes massive amounts of resources to process and clean for human use, so we think treating it wisely is good for all of us.
In our home we “clustered” the rooms so that the locations of water use were as close to the water heater as possible. The water heater (a tank-less hybrid) will be placed in a closet adjoining both the bathtub and laundry room so that there is less than 6 feet of pipe to each. The bathroom sink is just across the room, with maybe 12 feet of pipe to the fixture. The longest run is to the kitchen sink, which is about 25 feet at most.
Also, we had our plumber run what is called a manifold, or “home run” system of piping. Instead of the typical “trunk and branch system”, which uses larger pipes as the main line, then reduces to smaller lines as it gets near fixtures, we went from a very short section 3/4 inch pipe directly to a series of 1/2 inch lines right away, so each fixture has its own “home run” line (we wanted to go with even smaller lines, like 3/8 inch or even 1/4 inch, but fittings are hard to find, plumbers don’t have tools to work with them, and current plumbing code may not allow it).
This greatly reduces the amount of water wasted before hot water arrives, and also the time waiting for that hot water. In fact, we did some calculations of the amount of water held by the pipes, and it turns out that the amount of water contained in the ENTIRE hot water supply system (not including the water heater itself) is less than 1/2 gallon! The picture below shows a typical trunk and branch plumbing system:
This illustration below shows a manifold, or “home run” plumbing system like we used in our home:
(these images are not ours, but were gathered from a Fine Homebuilding article online)
Another advantage of this system is that there aren’t fittings in the walls and floors to reduce pipe size. The only connections are at the start and finish of the lines, so a future leak is easy to find. The photo below shows the manifolds our plumber installed, which splits the water to each fixture:
To the right is the main water line and shutoff valve, which feeds all of the other lines. The larger lines reduce to smaller, dedicated lines via the black manifolds. As you can see, almost all of the fittings are in this small utility room, so if there is a leak, it will be here and accessible to fix. The water heater will hang on the wall above. Immediately to the right is the bathtub/shower and to the left is the laundry.
Lastly, another step we took to save hot water was to insulate the lines where they ran under the slab floor so that they do not lose much of their heat to the ground. This conserves heat between uses, so even less water is wasted waiting for hot water. In the end, we hope to have designed a system that will conserve water as well as cut costs of living for the homeowners.
To find out more about the EPA WaterSense label, go to: