Multi-Source Harvesting Systems

Water Harvesting Solutions for Multi-Source Water Reuse Systems


The objective for any water harvesting system is to make it as efficient as possible in replacing the greatest amount of potable municipal water with non-potable water collected on the property. Often that can be accomplished by using water from one source – like rooftop rainwater. But in many cases, the most efficient systems collect water from multiple on-site sources that could include rainwater, greywater (gray water) from showers and sinks, condensate from the cooling system and more. Those same systems can support multiple uses on-site like toilet flushing, irrigation and cooling tower make-up.

Rainwater is a notoriously inconsistent source for harvesting, depending on variable rain events day to day and week to week. In drier states like those in the Southwest, total average supply is often insufficient to meet the demand for non-potable water, preventing a single-source rainwater harvesting system from meeting a building’s water needs. And although grey water harvesting provides a more consistent supply of water than rainwater alone, some buildings do not produce enough grey water to meet demand either. In these cases, the best way to meet a building’s total non-potable water demand is to combine multiple water sources to maximize efficiency and thereby minimize the building’s impact on water resources and the environment.

We understand that each building project has a unique set of variables for non-potable water supply and demand, so Wahaso tailors each system to the specific characteristics of each project. Our Scoping stage quantifies all potential water conserving methods by evaluating each of a building’s available water sources (including rainwater and greywater produced by showers and sinks and more) and applications for reuse (including toilet flushing, irrigation and cooling tower make-up and others). This allows us to achieve our ultimate goal, which is to minimize the amount of municipal water required for non-potable uses.

Commercial water harvesting is still a new industry and the rules are still being written and interpreted by national and local code authorities. Generally, codes permitting and restricting the capture and reuse of greywater refer to untreated or partially treated greywater. So it is good policy that such a source is not held for any extended length of time and is not sprayed or exposed to the public. However, once raw greywater is properly filtered and sanitized—as Wahaso’s systems do— it technically is no longer “greywater” and becomes a new standard of “on-site treated non-potable water” just as rainwater and stormwater do when they are properly treated. We can then combine the treated water from multiple sources and use the “on-site treated non-potable water” for many applications safely while adhering to national and local codes.

A single system that can properly treat multiple on-site water sources for multiple applications is more complex than a simple system that might only harvest rainwater. These systems require the experience and technical expertise that Wahaso offers. We have successfully designed and built dozens of unique multi-source, multi-use systems.

New York Sanitation Building

One of our earlier projects involved the new sanitation building for New York City and was designed with Greeley and Hansen engineers. The city was designing a massive new building to eventually house half the sanitation trucks for Manhattan, and the city wanted the project to achieve LEED certification for sustainability. Projected water demand included wash water for the trucks as well as showers and toilet flushes for the 108 workers supporting reuse collection. During our Scoping stage we identified abundant potential sources of on-site water for harvesting, which included an estimated 4.3 million gallons per year of condensate from the building’s steam heating system. It was an ideal source for harvesting. Our team custom-designed a system that harvested water from the building’s roof and condensate sources and applied them to cooling tower make-up, toilet flushing, truck washing and green roof irrigation, saving the city nearly four million gallons of water per year. The building will be commissioned in early 2014.

Oftentimes, the incremental cost of adding additional water sources or uses for a single processing system can be minimal – perhaps 5-10%, but the impact on total water savings can be significant – 40-100% improvement. That increase in efficiency translates into real annual savings in municipal water and sewer charges and the ROI for the entire system. Because we strive to conserve the maximum amount of water, we firmly believe multi-source systems are a worthy investment. The small incremental cost will quickly amount to substantial savings and significantly reduced water consumption.

We are happy to work with you to Scope your project and optimize a multi-source, multi-use system tailored to your unique property. To get started, just Contact Us.