Faster Hot Water Delivery Significantly Increases Hot Water Waste

August 23, 2019 3 min read

It is commonly believed that reducing structural waste by delivering hot water quickly to the point of use, such as Hot Water Recirculation, will produce a behavior change in bathers resulting in a significant reduction in behavioral waste. However, analysis of the LBNL data suggests that there is no correlation between low structural waste and reduced behavioral waste. In fact, bathrooms with consistently fast hot water delivery times (20 seconds or less) showed significantly more behavioral waste than average.

Specifically 50% of the bathrooms monitored by the LBNL system exhibited consistently fast hot water delivery, yet those bathrooms also exhibited 32% more behavioral waste than average.

Rather than significantly reducing the total amount of warm-up waste (structural waste + behavioral waste), fast hot water delivery primarily increased the percentage of behavioral waste within a relatively consistent warm-up waste volume.

The ShowerStart TSV produced by Evolve Technologies LLC is an effective tool for eliminating behavioral waste without requiring behavior change. As such, it is essential for guaranteeing the deemed savings commonly attributed to efficient plumbing configurations and products capable of reducing structural waste i.e. hot water recirculation systems.

Tub/Shower Combo Units

The Tub Spout Solution?: One therefore may conclude that the quicker the water can be purged, such as through the tub spout which flows at 5 gallons per minute, the less total gallons lost. Not exactly… This thinking rassumes the user must be accustomed to this behavior and, more importantly, be standing nearby ready to hop in as soon as the hot water arrives in order to not waste Hot Water(water & energy) at 5 gallons per minute that it is exiting the tub spout! Since most bathers constantly walk away while their shower/bath are warming up, despite how quickly this occurs, this method is a gamble at best.

What if the tub would pause at the precise time the hot water arrived?

Evolve's Auto-Diverting Tub Spout System does just that. For tub/shower combinations, as soon as hot water arrives, our system stops the flow out the tub spout, preventing Hot Water (both water & energy) from being wasted while no one is in the shower. At this time, the shower head will begin to trickle, letting the user know its warm and waiting.

With our Showerstart technology, the user decides when to return to begin bathing (typically when they finish their task at hand such as picking out clothes, using the toilet, shaving, etc). The water in the pipes remains warm (the trickle will allow for any additional cooled water to escape) and the user simply activates the shower head to begin normal flow at the rate the shower head is indented. If a bath is preferred, simply activate the tub spout instead. The system will automatically reset itself for the next user. how it works graphic

Stand Alone Showers (no tub)

Utilizing Evolve's Showerstart technology, either in our specialized showerhead (avaiable in multiple flow rates and features) or our TSV adapter placed between one's exisiting showerhead and pipe, eliminates the additional waste created once the hot water arrives. As the hot water reaches the shower head at precisely 95°, the flow will pause to a trickle. This trickle is just enough to let the user know the shower is ready and waiting as well as allow for any cooling water to escape if the user is distracted for an extended period of time. The Showerhead will continue to trickle until the user completes their task(s).


Elimination of Behavioral Waste even for homes with recirc systems can be achieved with Evolve's ShowerStart Technology.

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