Plumbing and water efficiency myths

Plumbing and water efficiency myths

Over the past 15 years we have had rumors, claims and outright assertions of savings by people associated with plumbing products or water efficiency programs.

Some of the claims were true; others not quite. Some claims are recent; others are ancient and should have been dismissed long ago.

It is likely that designers and program professionals will encounter myths from time to time, and they should be able to identify them. It is hoped that this article will set the record straight on some popular myths.

Let’s start by defining a term that is gaining attention – ‘greenwashing’, the act of misleading consumers regarding the environmental practices of a company or the environmental benefits of a product or service.

In green building initiatives, claims of water savings through the use of a specific products or practices that are unsubstantiated or based on suspect ‘engineering estimates’ would be examples of greenwashing.

The excellent paper Six Sins of Greenwashing from TerraChoice reports on a study of more than 1,000 products and the false or misleading claims of environmental benefits. The report identified the following sins:
• The hidden trade-off
• No proof
• Vagueness
• Irrelevance
• The lesser of two evils
• Lying

We see some evidence of all six in the plumbing and water efficiency sector – refer to the following examples.

Myth: Sensor-activated lavatory taps save water over manual taps (sin of no proof).
Reality: We have yet to see an independent scientific study that validates this claim. On the other hand, there are four ‘real world’ field studies demonstrating that manual taps are actually more efficient.

Study Date Change in water use
ASHRAE: Field Test of a Photovoltaic Water Heater 2002 +58% when manual taps replaced with sensor taps
Millennium Dome, London 2002 100% increase with infra-red sensor taps when compared with manual taps
Office building, California 2007 +40% when manual taps replaced with sensor taps
Office building, Florida 2008 +30% when manual taps replaced with sensor taps

The sanitary merits of ‘touch-free’ fixtures are without question, and manufacturers should confine their claims of benefits to that single attribute.

Myth: Tankless water heaters are more water-efficient than storage tank heaters in residential applications (sin of fibbing).
Reality: Here is an example of marketing and sales personnel exaggerating the benefits of their product by claiming savings that do not exist.

A recent Australian study found increased water waste associated with tankless heaters. In addition, there is evidence that people actually use more water by taking longer showers fed by a tankless heater. (In fact, some websites promote the fact that you can take longer showers without ever running out of hot water.)

What’s more, tankless heaters generally require a minimum flow rate through the unit to activate the heating components. In these cases, the first flow from a tankless water heater is cold, resulting in a longer waiting time for hot water.

Myth: Alternate-day watering of the lawn or garden saves water (sin of no proof).
Reality: Most experts agree that watering deeply once or twice a week is far better for the health of your lawn than frequent shallow watering, as deep watering promotes deep root growth. Many water efficiency experts believe odd/even restrictions promote over-watering by reminding people to water every second day.

Myth: Residential use of rainwater tanks will reduce peak summer irrigation demands (sin of no proof).
Reality: Many councils rebate rainwater tanks. However, such tanks do not hold enough water to be useful for landscape irrigation. A typical 190L tank holds enough water to apply 25mm of water to about 7.5m2 of lawn. And after an extended dry period, when irrigation is most needed, the tank is likely to be empty.

Myth: Automatic irrigation systems are more water-efficient than manually operated systems (sin of vagueness).
Reality: Although automatic systems can be very efficient, several ‘real life’ monitoring projects verify that automatic irrigation systems are typically operated in such a way that they apply far more water than manual systems.

The use of ‘smart controllers’ (also known as weather-based controllers) can improve the efficiency of automatic irrigation systems, but only if they are programmed and operated properly and are connected to an efficient, properly maintained system.

Myth: Water-cooled ice-making machines use less energy than air-cooled machines (sin of hidden trade-off).
Reality: This argument was broadly accepted until water authorities and others began to investigate and quantify the amount of energy embedded in the water itself, before and after its delivery to the customer.

That is, all of the energy associated with water treatment, delivery to the customer and collection and treatment of wastewater was found to be significant. When all energy use is accounted for (including energy used by the machine itself), it was found that air-cooled machines are the most energy efficient.

What to do?

Avoiding the tempting and easy path is essential to ridding ourselves of greenwashing claims. That is, we must be diligent and question what we hear or read about supposed water-efficient products or practices.

We need to be sceptical and seriously investigate claims of water or energy savings. We need to ask questions and look for a scientific basis behind the efficiency statements.

Here are some items to consider when going through that process:

• Products and practices should be subjected to independent analyses and measurement by qualified authorities. Verification of actual water use under conditions in the field is highly desirable. When that opportunity is not available, independent evaluations in a laboratory may provide reliable information.

• Where possible, do not rely on ‘engineering estimates’ of water use. This approach is simple but exceedingly unreliable, for it provides little in the way of real-world operating context.

• Field and laboratory studies that seem to focus on gathering reliable water use data may be doing the opposite. Products that are non-representative of the whole (samples cherry-picked for use in a study may not represent those in the manufacturer’s warehouse) and failure to account for the statistical reliability of the study can readily invalidate findings.

• A full lifecycle cost analysis is essential for some products, particularly those with extraordinarily high operating and maintenance costs. Products are often promoted as ‘green’ without regard for these continuing obligations. Building managers and owners that discover these previously hidden costs may remove the product before its physical life has ended.

• Meeting and hearing from professional colleagues is always welcome, but success stories often show only one side. Individuals are reluctant to stand up at a conference and tell colleagues of their failed products or programs – only the successes are presented. We should always seek all the information, good and bad, before making a decision to proceed.

• People involved in green building design and specification development are often approached by sales engineers and marketers. Slick, convincing arguments for a product or practice that have little or no basis in fact can ‘romance’ a novice in the field.

There is no substitute for scepticism and seeking the facts. Look for independent field and lab studies, customer surveys and authoritative data from independent sources such as water utilities and water efficiency professionals.

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