Last checked: October 22, 2026

Data centers and water testing

If a data center or any other big water user is coming to your area, the most useful thing a well owner can do is measure the well before it starts. You can't show a change without a starting point. This page covers what to measure and test in your own well, how to keep the records, and, for comparison, how data center cooling water and discharges are tested.

Part 1: Testing your own well

Why test before anything changes

USGS has documented that pumping can change water quality as well as water levels. In five U.S. aquifer systems, changes in groundwater flow from pumping and well construction mixed chemically different waters. That released naturally occurring uranium, arsenic or radium, which then reached supply wells.¹ Near the coast, or where salty water lies deeper underground, heavy local pumping can pull saltwater into wells (lateral intrusion or "upconing").³⁴ These effects depend on local geology, and none of these USGS studies was about data centers. They're the reason to cover more than the basics in a baseline.

What to measure and test

Not every well needs every test. Your state program or health department can tell you what's worth adding where you live. Compare your numbers with EPA benchmarks in our Well Test Results Checker, and see reading your test results for units.

How to sample and document

1. Use a state-certified lab, and follow its bottle and holding-time instructions.⁶
2. Sample from the same tap each time, ideally before any treatment equipment, and write down whether it was raw or treated water.
3. Get the water level and yield measured by a licensed well contractor. Ask for the method, the date, and how long the pump was off beforehand. Levels change with the season and drop in droughts, so compare readings from the same season.⁵
4. Keep a dated file: lab reports, water-level readings, your well log (find yours on your state page), pump service invoices, and photos of any sediment or staining.
5. Note what's happening nearby, with dates: construction starting, blasting, dewatering, a drought, or when the facility began operating.
6. If something changes, retest, call a contractor, and contact your state's water-rights or groundwater agency. Some states, such as Indiana, will investigate well failures near high-capacity pumping.⁸ More on this in Will a nearby data center affect my well?

Part 2: How data center cooling water is tested

This is the operator's job, not yours, but knowing how it works helps when you read permits or ask questions at hearings.

Conductivity and cycles of concentration

Cooling towers are usually controlled by conductivity, a stand-in for dissolved minerals. DOE recommends a conductivity controller that drains (blows down) water only when a set point is passed, flow meters on the make-up and blowdown lines, and a log of volumes, conductivity and cycles of concentration to spot problems.⁹ If the flow ratio and the conductivity ratio don't match, DOE says to check for leaks or other water losses.⁹ GSA's guidance for federal buildings calls for monthly water-quality checks, including monthly conductivity or TDS of make-up and system water.¹⁰

Scale and corrosion

• Corrosion coupons: small metal strips placed in the system and weighed later. GSA's facility standard requires quarterly measurement and notes 90-day coupons are more accurate than 30-day ones. GSA recommends weekly microbiological checks and monthly scale and deposit checks.¹⁰
• Scaling indices: the Langelier Saturation Index (LSI) and Ryznar Stability Index estimate whether water tends to form calcium carbonate scale or to corrode mild steel. A DOE technical report notes towers are typically kept slightly on the scaling side to avoid corrosion.¹¹ EPA cautions that these indices predict scaling only and say nothing about lead or copper corrosion.¹²

Legionella

CDC calls routine Legionella testing over time the best way to confirm that a cooling tower's water management program is working.¹³ CDC's routine-testing guidance says:¹⁴

• Growth looks well controlled below 10 CFU/mL in a cooling tower. At 10 CFU/mL or more, conditions may allow growth. A 10- to 100-fold increase means poorly controlled growth, and more than 100-fold means uncontrolled.
• Culture tests take about 7–14 days. DNA-based (PCR) tests are faster but may not tell live bacteria from dead.
• Results don't measure health risk, and there's no known safe level of Legionella. Any detection should trigger a response.
• After remediation, retest at least 48 hours after the system is back to normal operation.

These programs follow ASHRAE Standard 188 and Guideline 12. Testing for disease investigations is done with public health authorities.¹⁴¹⁵

Discharge monitoring

What gets tested in the wastewater depends on the permit. A data center that sends blowdown to a city sewer is regulated through the local pretreatment program. One that discharges to a stream needs an NPDES permit with its own limits.¹⁶ CRS says blowdown typically carries concentrated dissolved solids, possibly chlorine and treatment chemicals, and corrosion metals such as copper, nickel and chromium.¹⁶ For example, Tennessee's permit for the Memphis plant that will recycle sewage into cooling water for xAI and others requires limits for CBOD5 or ammonia, total suspended solids, E. coli, pH and residual chlorine. It also bars discharging the recycled water.¹⁷ EPA's ECHO database lets anyone look up permitted facilities and their compliance records.¹⁸

Frequently asked questions

What's the single most useful thing to do before a data center opens nearby? Get a dated static water level reading and a basic lab panel (coliform, nitrate, TDS, pH) from a certified lab. Add chloride, arsenic and uranium if they're relevant where you live.⁶¹

Will testing prove the data center caused a problem? No. It shows what changed and when. Deciding the cause takes a hydrogeologic investigation, often by a state agency.⁸¹⁹

Can I see the data center's own water test results? Usually not the cooling-tower records, which stay with the operator. Discharge permits and compliance records are often public through the state or EPA's ECHO.¹⁸ Some states now require water-use reports.²⁰

Related guides

• How to document your well before nearby construction or heavy pumping
• Who regulates big groundwater pumpers? Finding permit applications near you
• Will a nearby data center affect my well?
• Data centers and water: how much they use, where it comes from, and the rules
• How data centers treat cooling water
• Well Test Results Checker
• How often should you test a private well?