Did you know that, on average, people take 0.69 showers per day?

Did you know that the average shower lasts 7.8 minutes?

Did you know that showering uses a lot of water? Showering currently accounts for almost 20% of all indoor residential water demand!

There is no question that many people want to be environmentally responsible and use our natural resources—including water—more efficiently. But do low flow showerheads actually save water? Or do lower flow rates simply mean people take longer showers—thus negating any potential water savings?

To answer this question, Bill Gauley and John Koeller analyzed data for more than 50,000 shower events [1]! Shower volumes were determined by multiplying the flow rate by the duration. The results were very clear (see Figure 1 below).

  • People do not significantly compensate for lower flow rates by increasing the length of their shower. For every 0.2 gallon per minute (gpm) decrease in flow rate, shower duration only increased by about 5 seconds.
  • Lower flow showerheads do result in a lower overall shower volume. For every 0.2 gpm decrease in flow rate, shower volume decreased by 1.34 gallons

In fact, it seems that people tend to follow their own unique routine for showering regardless of the flow rate of the showerhead (at least for those showers between flow rates of 1.0 to 4.0 gpm). For example, if you take an 8-minute shower with a flow rate of 2.5 gpm (the current federal standard), then you are likely to take an 8-minute and 12-second shower with a flow rate of 2.0 gpm (the current U.S. EPA WaterSense® standard). But the total water used during your shower will decline from 20.0 gallons to only about 16.4 gallons!

While studies have shown that people tend to prefer higher flow rate showerheads [2], the results of this analysis clearly show that water savings can be achieved by using lower flow rate showerheads. As a result, water and energy utilities interested in achieving higher levels of water savings are rebating high-performance low flow rate showerheads.

The complete report can be found here.

Please send any questions to the authors:

Bill Gauley, P.Eng., Principal, Gauley Associates Ltd., bill@gauley.ca

John Koeller, P.E., Principal, Koeller & Company, koeller@earthlink.net

 

[1] Data from 1999 and 2016 Residential End Uses of Water Studies (REUS1999 and REUS2016) completed by Aquacraft, Inc.  Data provided by Co-Principal Investigator, Peter Mayer, P.E.

[2] High-Efficiency Showerhead Performance Study, 2009, Gauley, Robinson, Elton.  Report can be found at: http://www.map-testing.com/assets/files/Veritec-Waterloo%20Final%20...

This blog originally appeared on www.homeenergy.org.

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Comment by tedkidd on April 6, 2017 at 12:32pm

Interesting! 

Love to see an overlay of flow rate to client satisfaction. What flow is too low to provide a generally acceptable showering experience?

When do people simply replace for a higher flow after a few weeks of suffering?

Comment by Bruce Ackerman on April 6, 2017 at 9:45am

Excellent article, thank you so much. It frustrates me how little attention is given showers and showerheads, given the large usage of heated water they represent. As the authors confirm, people "don't like" low flow showerheads. First, there is at least one that the picky people in my household love -- a Delta 75153, rated at 1.2-1.5 gpm, that actually has internal moving parts and supposedly produces hollow droplets! We've used these for years, at 60-80psi, and I've given many as gifts, and report 100% satisfaction and 0 problems.

Why isn't something as good as this everywhere? Why do hotel showers suck (the financial incentive is certainly there to do better)?

LED lighting has similarly advanced, and indeed there's the ongoing educational challenge of updating the impression that they are ugly, like the early ones and most CFLs were, but it is gradually happening -- the stores all sell good LEDs and people do buy them. But what's missing with shower heads? Home Depot is the only retail store I even know of where I can buy this model, and it's on the shelf by the floor.

Is the shower such a private, sexually charged, whatever place that it is "untouchable" by conversations about efficiency? I feel like it's something like that, something psychological on some level (retailers, manufacturers, consumers?) but I'm not the one to suss it out. Frustrating though, and a huge missed opportunity.

Comment by Brad Cook on April 6, 2017 at 8:12am

I have been measuring the flow rate of every shower head as part of an energy assessment in a wide range of (mostly old) housing. After measuring hundreds of shower heads, I very rarely find one that flows at greater than 2.0 GPM. Many of those homes are served by private wells, which typically operate at 30-50 psi. That may skew my numbers lower, since much of the U.S. population is served by community water often at 80+ psi, where flowrate is proportional to pressure difference.

As Steve W. noted, I recommend replacing the tub spout (or overhaul the third valve) if water dripping from the tub spout is faster than distinct drops (eg- a pencil stream) with the shower running.

Comment by Steve Waclo on April 5, 2017 at 11:16am
Excellent article and here is another fun fact about showers: leaky diverted valves may be a sgnificant source of water waste.

http://www.taitem.com/wp-content/uploads/Diverter-Valve-Tech-Tip-20...

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