CSU Stanislaus rainwater pond inlet

CSU Stanislaus Cooling Tower Reclaimed Water Project

Facility managers at CSU Stanislaus are conserving potable water and managing drought-year restrictions through creative uses of its unique water reclamation system. The system collects millions of gallons of rainwater water from all 220 acres of the campus — parking areas, streets, roofs and landscaped areas — then filters it and stores it in a series of lakes and ponds having a total capacity of approximately 12 millions gallons. The system supplies all campus irrigation needs without tapping into potable water sources, and in keeping with the practices of sustainability, the irrigation pumping station is partially powered by a photovoltaic array. In addition to storing water for irrigation, these lakes provide attractive landscape features.

Innovative engineering and installation by campus staff enabled new uses for a campus-wide reclaimed water system, reducing potable water use by 22 percent, and meeting state mandated reductions.

Until recently, one of the largest demands for potable water on campus was the central plant chiller and cooling tower system. However a project completed in 2015 switched the source of the central plant cooling towers to the reclaimed rainwater system, thereby reducing campus potable water use by five million gallons annually, equivalent to 22 percent of the previous total campus usage. The project was driven, in part, by a need to comply with state mandates to conserve water imposed during a four-year drought period.

CSU Stanislaus cooling tower

Converting these central plant cooling towers to operate with reclaimed water reduced annual campus water use by five million gallons.

The impressive savings were accomplished through a straightforward engineering solution. The project team installed a metered connection from the irrigation system, using labeled purple pipe located at least ten-feet from any potable water line, as required for all reclaimed water systems. A high-efficiency five-micron filter with a UV component maintains water quality appropriate for cooling tower use. A sophisticated control system monitors water levels in storage ponds, the rate of water flows for irrigation, and water use in the cooling towers. The existing potable water line was retained as a backup in case of severe drought. Much of this work was done by campus staff, including plumbers, building service engineers and electricians, who installed filters, piping and electrical conduit.

In addition to using reclaimed water as the new source, the project included modifications to the piping and additional metering so that cooling tower “blow-down” (a process done to flush minerals from the system) could be sent to the irrigation storage system, saving an additional two million gallons of water that would otherwise go to the city sewer system. All together these measures are reducing utility costs from potable water use, sewer fees and electricity for pumping, saving approximately $22,000 annually.

CSU Stanislaus irrigation pumping station

This pumping station directs runoff captured from campus drains and streets to the irrigation system.

To inform stakeholders about the project, project leaders created a website to inform faculty, staff and the surrounding community of the campus’s efforts to capture, store and save water. The project team engaged students, presented the project in the classroom, and provided tours of the water system features. The campus has also documented the water reclamation system in a number of web pages and articles (see links in sidebar).

While this project has led to impressive water savings, campus facility managers plan to seek additional opportunities in the future. For example, in times of intense rainfall when the water storage is at capacity, it would be preferable to allow water to replenish the aquifer rather than allowing it to flow into storm drains as done currently. As they have done in the past, campus water managers continue to seek savings through innovations that may serve as models for other campuses.

Images © CSU Stanislaus. More at the CSUC water website.

Share this Case Study
Award Category
Key Features
  • Eliminated potable water from central plant cooling tower operation
  • High efficiency filtration and UV treatment
  • Reclamation of cooling tower blow-down for irrigation
  • Campus outreach to stakeholders
  • Installation primarily by campus staff
Annual Estimated Water and Cost Savings
Completion Date
Project Team