The Other Half of Water Conservation

Low-flow fixtures are important, but if you're really serious about saving water you may need to re-think your plumbing system.

The Other Half of Water Conservation

 By Tim Kampert

Bathrooms account for more than 50 percent of all indoor water use, according to the EPA. That makes WaterSense fixtures a great choice for any project, and a must for anyone claiming to build green homes. But while low-flow fixtures are important they're not the whole story. In my experience as a building performance specialist working with production builders across the U.S., I have learned that there is plenty of additional savings to be gained from more efficient plumbing.

It's not uncommon for a homeowner to flush thousands of gallons down the drain each year waiting for hot water to reach the tap. The effect on the water bill is certainly an issue here, but so is homeowners' frustration with that wait time. In fact, a common complaint our builder clients hear from homeowners is that "it takes forever to get hot water."

Considering the frequency of those complaints I'm surprised more builders don't do something about them. The truth is that wait time is actually easy to fix and won't add to job costs.

The underlying problem is one of benign neglect. Builders don't include plumbing layouts on their plans because they assume it's the plumber's job to determine where the pipes will go. But if the pipe layouts I see in many homes are any indication, most plumbers give little if any thought to wait time.

Those water-saving fixtures can actually increase the frustration. When a faucet or showerhead has a lower flow rate than older models, fewer gallons per minute will pass through it and hot water will take longer to reach it.

Some custom builders keep hot water at the tap by installing point of use heaters near critical fixtures or with a hot water recirculation pump. A recent field study found that domestic hot water circulation can save an average of 4500 gallons per year.1

But while these devices get the job done, they're too costly for most production homes, especially at the lower end of the price spectrum. They also raise the homeowner's energy bills, something high-performance builders work hard to avoid.

A better alternative for production homes is a deliberate plumbing layout that's structured to reduce pipe runs. It offers the same benefit as a point-of-use heater and adds nothing to the job costs—in fact, it requires less pipe so it will probably save the builder a few dollars. It will eliminate wasted water as well as a lot of those homeowner complaints.

Shortening Runs

The most obvious step the builder can take to reduce pipe runs is to re-locate the water heater. In most homes, the water heater is in the garage, far from the taps. I prefer to see it in a central closet (not in the attic, however: a water leak there can be catastrophic).

Putting the water heater inside the home will, of course, reduce the amount of interior space by a few square feet. However, consider getting customer feedback on whether the space lost to a small utility closet is worth the price of those thousands of gallons of wasted water and those long wait times. You may find that the benefits of that central location are actually a sales advantage.

The other step is the structured plumbing layout mentioned above. The plans given to the plumber need to show the location of all pipe runs and the builder needs to make sure the plumber follows that plan. Of course, that means the field managers have to check to make sure the job was actually done to plan.

The plan should require that the supply loop in a trunk-and-branch layout be routed as close to the fixtures as possible. That will shorten the drops that branch off of it. The ideal length of a drop is less than six feet.

PEX systems can have drops of varying length originating from multiport tees placed close to fixture groups. When designed correctly, this approach goes a long way toward shortening runs. It's best to locate each tee where the fixture with the highest flow rate will be served by the shortest drop.


Tim Kampert is a building performance specialist on the PERFORM Builder Solutions team at IBACOS. A version of this article originally appeared on


1 From a presentation given by Haley Monson of the Elsinore Valley Municipal Water District in California at the Water Smart Innovations Conference on October 2-3, 2019.


View User Profile for ED MCGUIRE

re: The Other Half of Water Conservation

Friday, November 1, 2019 9:42:10 AM

Your illustration is definitely not showing the shortest possible run to the bathroom.

re: The Other Half of Water Conservation

Friday, November 1, 2019 10:23:44 AM

Through the DOE ZERH program and PHIUS we've learned about the on-demand recirc pumps like the Act D'mand Kontrols system. We don't do production homes, so I can't address the cost those builders are facing, but the way we see it, the combination of quick hot water and reduced energy losses are very desirable and easily paid for with other available selections in the design process, from various finish specs to smarter use of square footage (smaller overall house size). The concept is that the recirc line runs within 5' of every hot water tap, and wireless switches can be placed wherever make sense for the owners' convenience. 

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