Warm-Up Waste is the water that unintentionally runs down the drain before one steps-in the shower and begins showering. Three primary factors contribute to its existence:
• Long plumbing runs from the water heater to the shower,
• Reduced shower head flow rates, and
• Bather behavior produced by the increasing hot water waits associated with the above factors
Lawrence Berkeley National Laboratory (LBNL), under the direction of Jim Lutz, has a history of analyzing the water and energy waste associated with Warm-Up Waste and has published two known papers on the topic, Feasibility Study and Roadmap to Improve Residential Hot Water Distribution Systemsand Water and Energy Wasted During Residential Shower Events. In the first paper, Lutz used a mathematical formula to analyze more than 26,000 shower events within the REUWS 1999 database and surmised that approximately 20% of the total volume of water used for showering was Warm-Up Waste. The second paper, a field study designed by Lutz, concluded that the average volume of water consumed by Warm-Up Waste was closer to 30% of the total shower volume.
Independent research contained in a Pilot Study For A Thermostatic Shower Restriction Valve by Cadmus on behalf of PPL Electric indicates bathers are spending approximately two minutes away from the shower during Warm-Up. Given that the average shower lasts~ 8 minutes, this data aligns very well with the conclusions of Lutz from Lawrence Berkeley National Lab.
In total, about 2 minutes or 25% of a shower’s water and energy volume are consumed by Warm-Up Waste.
The federal government first began regulating showerhead flow rates in 1992 by passing the Energy Policy Act. It, among other things, limited showerhead flow rates to a maximum of 2.5pgm. Before then, showerheads were unregulated and could easily consume 3-5gallons per minute depending on a home’s water pressure.
2010 introduced the first WaterSense specification for showerheads. It limited showerhead flow rates to a maximum of 2.0 gpm and mandated minimum performance thresholds for both spray force and spray coverage. Its objective was to stimulate savings greater than the federal 2.5 gpm by ensuring bathers received a high-quality, yet more efficient, shower experience.
In 2018, the California Energy Commission codified new Title 20 Water Efficiency standards mandating maximum showerhead flow rates of 1.8 gpm. Given the influence and population size of California, 1.8 gpm showerheads have now become the defacto national standard for all showerheads sold at the nation’s largest brick and mortar retailers including, but not limited to Costco, Home Depot, Lowe’s, Target and Walmart.
At the same time, the nation’s largest utility-based water and energy efficiency programs have adopted even lower maximum shower head flow rates in a continual effort to stay ahead of the rapidly declining market baseline. As a result, today’s utility program showerheads are generally standardized around 1.5 gpm showerheads and they are beginning to migrate to flow’s as low as 1.25 gpm.
It’s easy to understand that reductions in showerhead flow rates from as high as 5 gpm to as low as 1.25 gpm would increase hot water waits. After all, it’s logical to assume, for example,that hot water waits for a 1.5 gpm showerhead would be 2X those for a 3.0 gpm showerhead. However, the actual impact of lower flow rates on hot water waits is much greater than believed. This is due to an increased thermal loss associated with slow moving hot water as it journeys from the water heater to the shower.
Research presented by John Koeller in Evaluation of Potential Best Management Practices -Residential Hot Water Distribution,indicates the impact on hot water waits imposed by lower flow rate showerheads is exponential, not linear due to these increased thermal losses. As a result, flow rates of 1 gpm or less on the hot water line,a common occurrence with WaterSense rated shower heads, increases the volume of Structural Waste that must be purged before hot water arrives. The effect is a50% to 100% increase in the actual volume of Structural Waste that must be removed. In other words, bathers now have to remove more non-bathing temperature water than the volume of water residing in the hot water line. The thermal losses of slow-moving hot water create an incremental volume of lukewarm water (Structural Waste) that must also be removed before bathing temperature water arrives. The result? In many cases today’s hot water waits (Warm-Up Waits) are up to 6X longer than they were in the early 90’s, and the only thing that changed in the home was the installation of water and energy efficient showerheads.
Due to the fact that Warm-Up Waste is instigated by plumbing structure, it is a difficult problem to solve.Relocating water heaters, rerouting plumbing lines, installing hot water recirculation loops or adding retrofit on-demand hot water pumps are generally not cost effective or practical solutions for improving water and energy efficiency by reducing hot water waits.
The challenge of solving the Warm-Up Waste problem grows even bigger once the human behavior factor is considered. As previously identified, waits as little as 20 seconds are long enough to prompt bathers to turn-on the shower and then leave to do something else while waiting for hot water to arrive. And, it’s very difficult, if not impossible to implement structural plumbing changes and enhancements that can consistently deliver hot water in less than 20 seconds.
There are, however, new products that innovatively address all or part of the Warm-Up Waste problem and they do so while adding both comfort and convenience to get-ready-routines. These inexpensive and innovative measures, depending on their particular feature sets eliminate all or the majority of Warm-Up Waste by leveraging the following comfort and convenience-based benefits:
· Fast Hot Water- Reduces Structural Waste by mitigating thermal losses as hot water initially travels to showerhead
· Repurpose Water- Offsets Residual Structural Waste by capturing and utilizing non-bathing water for other purposes
· Warm-Up Freedom- Eliminates Behavioral Waste by thermostatically stopping flow when hot water arrives
The simplest and most convenient method of Reducing Structural waste is delivering Fast Hot Water. This is most easily accomplished by bypassing the flow restricted showerhead as the cold water in the hot water line is being purged. There are two methods for accomplishing this.
· Tub Spout Warm-Up: The Structural Waste is purged at 5 gpm through the tub spout, and hot water,once it arrives, is diverted to the showerhead.
· Showerhead With Purge Port Warm-Up:The Structural Waste is purged at 5 gpm though an unrestricted purge-port integrated into a showerhead.
In both Warm-Up types, Offsetting Residual Structural Waste is easily achieved by collecting the non-bathing temperature water in a receptacle, such as a bucket or watering can, and repurposing it for home use. Examples include watering plants, hydrating pets, doing laundry, cleaning or even flushing toilets.
However, neither Fast Hot Water or Repurposing Water address the Behavioral aspect of Warm-Up Waste. And as previously mentioned, waits as little as 20 seconds are simply too long to encourage bathers to change their habits and remain by the shower while waiting for it to become warm. The solution? A thermostatic shut-off valve (TSV)integrated into the tub spout or showerhead that senses hot water arrival and automatically, yet temporarily, shuts off the flow until bathers return and begin showering.
This core Behavioral Waste eliminating technology, ShowerStart®, developed and patented by Evolve Technologies has been installed in more than 2.5 million homes over the past several years and has been awarded numerous US and international patents.
A new ShowerStart enhancement, capable of delivering Fast Hot Water, by purging Structural Waste through an Express Port at rates up to 5 gpm and then facilitating the Repurposing of that Water has been announced. Called ShowerStart Expressit Reduces Structural Waste, Offsets the Residual Structural Waste and eliminates Behavioral Waste.
Consumers gain the comfort and convenience benefits of Fast Hot Water, Repurposing Water and Warm-Up Freedom along with reduced water and energy costs. Utilities gain a simple, cost effective and consumer friendly solution for effortlessly, yet significantly, increasing a shower’s water and energy efficiency.