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Scan for outdated or missing drivers - takes under a minuteDriver Scan →Repair Windows errors before they cause bigger problemsFix Now →Data centers can reduce reliance on municipal potable water by changing either the water they use or how they reject heat. Reclaimed wastewater and captured onsite water can supply cooling-tower makeup after appropriate treatment; dry or hybrid cooling and suitable economizing can reduce the evaporation that creates makeup demand in the first place. These are different strategies, and neither reclaimed water nor liquid-cooled servers automatically means a facility uses no potable water or cooling towers.
Start by separating the water source from the cooling method
A cooling system has at least two relevant choices: how it moves heat away from IT equipment, and where it gets the water it may consume. Replacing potable tower makeup with reclaimed water changes the source, but a cooling tower can still evaporate water. Changing to a dry heat-rejection system can reduce evaporation, but it does not by itself determine what water the rest of a facility needs.
Compare proposals across the whole heat-rejection path, not just at the server rack. Include direct potable water consumed, source reliability and drought exposure, electricity use and peak power, evaporative versus dry operation, water chemistry and treatment residuals, and any indirect water impacts from electricity where those can be assessed. Climate suitability, retrofit compatibility, operating complexity, and opportunities to reuse heat also affect the decision.
Can data centers use reclaimed or captured water for cooling?
Yes. The U.S. Environmental Protection Agency identifies reclaimed municipal wastewater, HVAC condensate, rainwater or stormwater, and treated greywater as potential sources for cooling-tower makeup. Each requires a site-specific assessment: availability and conveyance, seasonal reliability, treatment, water chemistry, and health and cross-connection controls all matter. Untreated greywater or stormwater should not be assumed suitable for a cooling tower.
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Reclaimed municipal wastewater
A municipal reuse system can provide a substantial alternative supply where a utility can deliver water of compatible quality. The City of Quincy, Washington, and Microsoft developed the Quincy Water Reuse Utility to treat cooling water from Microsoft’s data center. The utility became operational on June 30, 2021, after more than ten years of planning and construction. EPA’s case study reports that, as of 2022, Microsoft’s campus was the only data-center campus connected.
The Quincy treatment system uses processes including softening, ultrafiltration, and reverse-osmosis infrastructure to remove salts before reuse. EPA estimates that it saves 138 million gallons per year of potable groundwater. That is a project-specific estimate tied to Quincy’s local source mix, treatment train, and infrastructure—not a general savings rate for data centers. The process also produces concentrated brine that is managed in lined ponds for disposal.
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The case illustrates why reuse is both a supply project and a water-quality project. Quincy’s mineral-rich groundwater and wastewater with high total dissolved solids created operational and municipal-treatment challenges. EPA also notes that canal makeup was unavailable during a hot, dry period in 2021, so the utility could switch to potable groundwater. Multiple sources improved resilience, but did not remove the need for contingency supply.
Condensate, rainwater, stormwater, and greywater
Onsite capture can make use of water that would otherwise be discharged or run off, but the usable volume varies with weather, building operation, and season. Storage, treatment, pathogen controls, and prevention of cross-connections with potable plumbing must be part of the design. EPA’s onsite-reuse work addresses pathogen-removal targets and cross-connection risks; cooling-tower applications also require attention to Legionella control.
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Does liquid cooling use less water?
Not necessarily. Direct liquid cooling changes how heat is collected from IT equipment; the downstream equipment determines how that heat leaves the facility. DOE describes direct liquid systems that transfer heat into a recirculating chilled-water loop. In some configurations, that loop transfers heat to a condenser-water loop and cooling tower, so tower evaporation can remain. Other system configurations differ.
Liquid cooling may reduce air movement and can improve power usage effectiveness (PUE) or water usage effectiveness (WUE) in some designs, but those outcomes are not guaranteed by the server-side technology alone. Ask for the proposed system’s full heat-rejection diagram and its expected water and energy use under the site’s operating conditions. The reviewed DOE guidance does not establish a general savings figure that applies across liquid cooling, immersion, dry cooling, and water reuse.
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Which cooling approaches change heat rejection or water demand?
| Approach | What it changes | Conditions and trade-offs |
|---|---|---|
| Reclaimed municipal wastewater | Supplies an alternative source for cooling-tower makeup. | Depends on local availability, conveyance, treatment capacity, compatible water chemistry, and reliable contingency sources. EPA’s Quincy case demonstrates a utility-scale reuse system, not a universal template. |
| Captured condensate, rainwater, stormwater, or treated greywater | Supplies onsite makeup water. | Capture volumes can vary; treatment, storage, pathogen controls, and cross-connection safeguards are important. |
| Air-side economizing | Uses suitable outdoor air to condition the data-center space, reducing mechanical cooling when conditions allow. | Potential savings depend on climate hours, outdoor humidity and air quality, and contaminant controls. Annual results vary by site. |
| Dry coolers or hybrid heat rejection | Rejects some or all heat to ambient air instead of relying only on evaporative towers. | Feasibility depends on ambient conditions and coolant temperatures. A hybrid system may retain evaporative operation during peak heat. |
| Reverse osmosis of cooling-tower blowdown | Recovers permeate for reuse as tower makeup. | Can offset freshwater demand, but adds energy use, operating requirements, and a concentrated reject stream that must be managed. |
| Cold underground thermal energy storage | Stores cooling capacity underground for use during peak demand. | DOE describes a funded project under exploration; the cited project overview does not establish standard deployment economics or guaranteed savings. |
Air-side and water-side economizing
Economizing takes advantage of conditions that let a facility use less mechanical cooling. Air-side economizing brings outdoor air into the cooling process and is most useful when temperature, humidity, and air quality are suitable. Controls must address contaminants and humidity; a favorable climate does not make every hour suitable.
DOE’s 2024 design guidance cites 20% less energy consumption at the chiller in the context of hot/cold aisle and airflow practices. That figure concerns energy in the cited context; it is not a general water-savings percentage or a promise for every facility.
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Tower operation and blowdown recovery
Cooling towers lose water through evaporation and blowdown. As evaporation concentrates minerals in the remaining water, blowdown removes some of that concentrated water to control chemistry. Operating at higher cycles of concentration can reduce blowdown and makeup needs, but the allowable operating point depends on system chemistry and other constraints.
Reverse osmosis can treat blowdown and return recovered permeate to the tower. DOE cautions that this adds energy use—which can worsen overall PUE—and operational requirements; the concentrated reject stream also needs a disposal or management plan. Evaluate the full water-and-energy balance rather than counting recovered water alone.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How should a facility choose among the options?
- Map the current system. Trace heat from the IT equipment through its cooling loops to the final heat-rejection equipment. Identify where water evaporates, where blowdown occurs, and which systems already use dry operation or economizing.
- Establish the water baseline. Separate potable water from reclaimed or captured sources, and distinguish water withdrawn from water actually consumed. Record seasonal demand rather than relying only on annual totals.
- Test supply reliability and quality. Check source availability during drought and peak heat, treatment needs, water chemistry, conveyance, and residual management. Include contingency sources in the plan.
- Model water and energy together. Compare annual and peak electricity use as well as direct water demand. Include the energy cost of treatment and the indirect water impacts of electricity where reliable local data are available.
- Check climate and retrofit constraints. Estimate the hours suitable for economizing and assess whether dry or hybrid equipment can meet required coolant temperatures during the hottest conditions. Consider building, rack, and operating changes required for liquid cooling.
- Plan safe operation and maintenance. Verify treatment, monitoring, pathogen controls, cross-connection safeguards, and procedures for brine or other residuals. Confirm that the operating team can manage the added equipment.
The Open Compute Project’s March 2026 overview frames cooling impacts as an interaction among energy, water, carbon, water scarcity, and heat reuse. That is a useful systems boundary: a lower-water design is not automatically the lowest-impact design if it substantially increases energy or creates other burdens. The right comparison depends on the facility’s IT load, climate, water availability, utility conditions, and existing infrastructure.
What a credible proposal should show
- A process diagram that identifies the server-side cooling method and every downstream heat-rejection stage.
- Water use by source and season, including potable-water consumption, reclaimed-water demand, and contingency supply.
- Expected electricity use and peak power alongside water figures, with assumptions stated for climate and operating conditions.
- Treatment requirements, water-chemistry limits, monitoring needs, and a plan for brine or other concentrated residuals.
- Evidence that economizing or dry operation can meet cooling needs during the site’s demanding weather conditions.
- Local review of reclaimed-water quality requirements, water rights, permitting, utility prices, and Legionella controls.
Requirements and water availability vary by location. EPA’s Quincy case is useful evidence that large-scale reuse can work with local utility planning and substantial treatment infrastructure; it does not establish that another site can reproduce the same supply, costs, or savings.
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