Case study: College uses ultra-low-flow water systems
Toward the end of 2012, CannonDesign was hired to design three new buildings on an aging California community college campus. Ohlone Community College, nestled on the side of a very large hill in Fremont, Calif., had just begun what would be a lengthy and extensive remodel of the campus. As the usual focus on energy efficiency began to take center stage, Ohlone also stated that another main goal was for these projects to be ultra-high-efficient with regard to water use. College administrators were interested in exploring every avenue of water conservation, not only because the state of California was in the midst of the worst droughts in their history and saving water was the right thing to do, but also because Ohlone saw a huge opportunity to educate students and staff on the importance of water conservation.
With the mission clearly identified, CannonDesign’s plumbing designers set out to reduce as much water use as possible. The most obvious area to explore was the plumbing fixtures.
Knowing the project would be held to the state’s CALGreen building codes along with targeting U.S. Green Building Council LEED Gold certification, the team set a lofty goal of 40% reduction in indoor water use. Although a 40% reduction is not impossible, it can sometimes be difficult to save that much water, especially in buildings that don’t have a single shower (typically the highest water user). Through much discussion, the team settled on 1.1-gal/flush (gpf) water closets (which are still very new), flushless urinals, 0.35-gpm lavatory faucets, and 1.5-gpm sink faucets throughout the new buildings. The calculated reduction from the baseline was roughly 3,240 gpd, or just more than 50%—a substantial savings.
With such a successful start, the design team continued to explore other obvious avenues.
Next on the list was water reuse. The stormwater system was considered, but it quickly became evident that although the college was located in the notoriously rainy Northern California area, Fremont only receives about 15 in. of yearly rainfall. To put this in context, the national average is around 37 in./yr and a desert is classified as 10 in./yr. The team determined it was not feasible to design a stormwater collection system for reuse as the amount of available rainwater would not sufficiently supply indoor water uses. Greywater was also considered, but the only viable supply of greywater would have come from lavatory faucets and kitchen sinks. With the application of ultra-low-flow fixtures, the calculations showed there wasn’t enough of a base to warrant collection and reuse of greywater.
With the obvious items having been explored, the design team needed to get creative. The equipment was next on the list, which is not typically thought of as a major water user. However, the team went back to the idea of education as their incentive. Water purification in a lab setting uses a considerable amount of potable water in the treatment process. According to filtration equipment manufacturers, estimates of up to 25% of water used in the purification process could go down the drain as waste. It quickly became apparent that this was just the avenue the owner was looking for to educate the building occupants. A small system was devised to collect and treat this process water and store it for reintroduction into the landscape irrigation system. To justify the system, it was also tied into the direct collection of the HVAC condensate from air conditioning systems, and it quickly became a decent reuse of two normally forgotten aspects of water use. Because the HVAC and landscape systems were already highly efficient (native vegetation and no cooling towers due to air-cooled chillers), the team had explored all of the possibilities of water savings.
The final strategy used in the new buildings was to sub-meter all water-using equipment (boilers, irrigation, ground loop, purified water, lab equipment, etc.) and display the information throughout the buildings in the form of a dashboard system. The team also provided thorough explanations of each system, and why each was designed a certain way, to give occupants a better understanding of how water can be used and tracked.
The aggressive methods used at Ohlone Community College’s new Academic Core Buildings is a perfect example of how a thorough understanding and investigation of a building’s functions and goals can result in a highly efficient building design in regards to water use.
Mark Graf is a senior associate at CannonDesign. As a plumbing and fire protection engineer, Graf provides engineering leadership across all markets and building typologies. He established CannonDesign’s water use unit to examine and develop water-conservation solutions.