Fight the invisible cost of wasted water

Fight the invisible cost of wasted water

When hot water goes down the drain, the invisible cost of heating the water uses more water than the wasted water.

In his analysis of the water- and energy-saving benefits of demand control pumps for homes, water consultant Dave Grieshop depicted the real costs of wasted water.

demand control pumpA demand-control pump circulates hot water through a home's plumbing system on demand. So instead of waiting 30 seconds for warm water to reach the shower, the demand control pump can cut the waiting time to just a few seconds. It pulls the hot water from the water heat through the plumbing system on demand, or at the touch of a button by the user. The pump runs only until the system measures the hot water moving through the pipes. Then it shuts off. The water is pumped through the plumbing system back to the water heater. It is not wasted down the drain, waiting for the water to warm up.

Grieshop provided an overview of results from the Cochise Water Project in Sierra Vista, Arizona, where he served as technical chair of the committee.

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:

Hot Water Saved (gal)3,271
Electricity Saved (USD)$61.48
Time Saved Waiting for Hot Water (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 strive 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!

Cost of Invisible Water

When it comes to hot water, the amount of invisible water required to heat water takes on major meaning, Grieshop said.

"Compare the 16,425 gallons of visible water heated annually in one home with the 10,108 gallons of annual invisible water required to heat the visible water, the need to minimize wasted hot water should be a national priority.

"Invisible water is almost non existent when it comes to cold/ambient water but everything changes once you deal with hot water. Some of the structured plumbing designs I have done for new residences have lead me to always look for at least two plumbing zones in new homes. The payoff in terms of invisible water savings accrue for decades."

The Water Cost of a Cup of Coffee

Grieshop related this thought as he was drinking his morning coffee.

"My European coffee pot is rated at 1.4 kW. I made 8 cups of coffee which is actually about 4 cups as I measured water for the water use studies. The coffee pot was on for roughly 15 minutes. So I used 0.375 kWh of electricity making the coffee. The National Renewable Energy Laboratory study shows that in Arizona consumptive water used per kWh of electricity produced is 7.8 gallons per kWh. So, in theory, I used 1.95 gallons of invisible water producing the one quart of hot coffee I am enjoying.

In other words, I used almost 8 times as much invisible water this morning making my pot of coffee with visible water that I am enjoying. I’ll wager you never thought of water that way!

Read more about water saving devices.

Topics: Plumbing & Fixtures, Water Heaters, Water Saving Devices, WaterSense

Companies: ACT D'MAND Systems

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