Demand control pumps could help battle water shortages

Demand control pumps could help battle water shortages

It's no secret the Western United States is facing severe water shortages that could have consequences for the entire country and the world. But there is one remedy that could dramatically save water in homes in the region, as well as around the world: the demand control pump.

Drought conditions

According to the U.S. Drought Monitor, 58 percent of California experienced “exceptional drought” conditions (the highest level of dryness) in July. Almost 50 percent of Nevada is currently in “extreme drought” conditions, with large pockets in Oklahoma and Texas in similar conditions.

The Colorado River Basin supplies water to major metropolitan regions like Los Angeles, and San Diego, and Las Vegas and Phoenix and the fear from scientists is that the Colorado River basin won't be able to meet its water supply commitments.

The current conditions have been the same for several years as reservoirs and aquifers progressively deplete through over use. The rising cost of water will bring far-reaching effects to the US economy and impact the profitability of water- intensive industries, such as agriculture, electrical generation and manufacturing.

Solutions available today

Here Dave Grieshop, a water conservation consultant, reviews the impact that demand control pumps can have in conserving water and energy in drought-stricken regions of the United States. The pumps also deliver on-demand hot water in any home, saving water and energy and delivering hot water faster at the same time. A demand control pump pulls hot water from the water heater while simultaneously sending cooled-off water from the hot-water lines back to the water heater, reducing the wait for hot water at a fixture, such as a shower or kitchen sink. The pump can be activated by a button or motion sensor in the room. The on demand pump pulls hot water from the water heater to the fixture, so it's ready when you are for hot water. It can be installed in a variety of plumbing configurations. Depending on the type of plumbing system in the home, the pump can be installed in the fixture farthest from the water heater, or in a return line to the water heater.

Hot Water in the Dry Southwest

by Dave Grieshop; managing partner; Reality LLC

What follows is one look at water (and energy) concerns in California, Arizona and Nevada. A collaborative study released in July 2014 by UC-Irvine, CA Institute of Technology, National Center for Atmospheric Research, and NASA shows that groundwater withdrawals in the Colorado River Basin have been greatly underestimated.  As Tom Hanks said in the movie Apollo 13 “Houston, we have a problem.”

A demand control pump provides energy savings and water savings, along with the convenience of having hot water on demand. When a demand control pump is installed, there’s no need towait for cold water to heat up because it’s already hot, on demand. Instead of a “cold start,” turning on the hot faucet is a “usable start.”

Later this year, I will present information at a conference regarding data I have collected on wasted water and time in private homes in southern Arizona.  Homeowners provided real behavioral data on wasted water and time while waiting for hot water at their kitchen sinks and at one fixture in their master bathrooms. Data were collected both before and after demand-controlled pumps (DCP) were installed in the homes.  (More than 130 DCPs were installed in 2013 via a rebate program sponsored by the Cochise Water Project, ( Ed note: Grieshop chairs the technical advisory committee for the Cochise Water Project. Read more about the project here.

See the data and calculations behind these numbers here.

The four weighted average values for wasted water and time down the drain while waiting for hot water are: 

Per Hot Water DemandWithout DCPWith DCP
Wasted Water (Cups)28.14.2
Wasted Time (Seconds)62.39.1


Assume the data above are representative for all homes in AZ, CA and NV - a total of 17.9 M (million) homes - all with 100% efficient electric hot water heaters which heat 45 gallons daily for use in each home.  First, let’s examine one average home in terms of annual hot water heated; the energy and water associated with that hot water; and, what I refer to as “invisible water.”  That is, the water consumed during electricity production at a thermoelectric and/or hydroelectric power plant; we use it but never see it in the home.  

Average Home (Annually)
Total visible water heated (gal)16,425
Electricity required (kWh) 2,287
Invisible water required for kWh (gal)   10,108


Waiting for Hot Water *Without DCPWith DCPSavings
Wasted water (gal)3,8465753,271
Cost to heat wasted water (USD)$72$11$61
Time per day waiting for hot water (min) 6:001:005:00
*Based on six (6) demands per day


The messages contained in the above are:  heating water takes energy – lots of it which is why the invisible water consumed is so significant.

A demand control pump from ACT D'MAND KONTROLS Systems.

A standard plumbed home (home without a DCP) wastes 23% of the daily hot water just waiting for hot water; a home with a DCP wastes 4%. The addition of a DCP reduces the invisible water required by 1,920 gallons and saves the homeowner $61 annually plus almost 3,300 gallons of water. This is the impact of the water-energy nexus. Finally, and most important to the homeowner is the convenience cited of not having to wait but a few seconds for hot water with a DCP installed.

Now let’s stretch the per-home results to the 17,900 K homes in AZ, CA and NV and glean the opportunity to impact water and energy savings via DCPs.  The daily hot water produced for all homes is 805 M gallons.

All Homes with DCPs (Daily Savings)
In-Home Gallons (Millions)  160 
Invisible Water Gallons (Millions)   98 
Total Gallons (Millions)  258 
Kilowatt Hour (Millions) 22 
All Homes with DCPs (Annual Savings)
Total Gallons (Billions)94 
Total kWh (Billions)   8 


These values speak for themselves and represent opportunity.

If you find the collaborative study noted above to be worrisome, this brief analysis addresses a portion of the issue we can do something about.  Maybe Tom Hanks should have said, “Houston, we are the problem.”  We can do better home-by-home.  What do you think?

Grieshop also provided a summary of his findings:

Summary Overview

For the average homeowner the impact of the annual hot water savings that accrue when installing a demand-controlled pump (DCP) are these:

Annual Savings After Installing DCP
Hot Water (gals) 3,271  
Electricity (USD)   61.48  
Time (hours)32.4  


Additionally, these annual benefits accrue from a water and electricity systems’ perspective due to the hot water savings by the average homeowner when installing a DCP:


Invisible Water Saved (gals)   1,941  
Invisible Electricity Saved (kWh)  439  


Why striving to avoid wasting hot water makes sense: it takes 27 times more electricity to heat hot water than it does to move water, hot or cold, in the first place!

Read more about the invisible cost of wasted hot water.

Lake Mead photo via Flickr/Raquel Baranow

Read more about water saving devices.

Topics: Bedroom, Cost of Ownership, Kitchen, Plumbing & Fixtures, Sustainability Trends & Statistics, Water Saving Devices

Companies: ACT D'MAND Systems

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