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How to Choose a Cooling Water Recovery System for a Data Center

Most data center water goes out through the cooling tower in two ways. Some evaporates, which is how the tower rejects heat. The rest leaves as blowdown, the water a tower drains to keep dissolved minerals from building up. The U.S. Department of Energy puts it as one line: makeup equals evaporation plus blowdown plus drift (FEMP Best Management Practice 10). Blowdown is the part a recovery system can treat and send back to the tower. Evaporation cannot be recovered by any system.

That one distinction decides most of what follows. Here is how to choose a recovery system for an existing plant, in the order the questions come up.

1. Measure before you compare

You need twelve months of your own numbers before any vendor proposal means anything:

  • Makeup and blowdown meter totals, by month
  • Cycles of concentration and the conductivity setpoint
  • Water and sewer bills with the rate schedule, and how sewer is billed. Fairfax County, Virginia bills commercial sewer on actual water consumption (Fairfax County), so recovered water lowers the sewer bill. Mesa, Arizona bills industrial wastewater on measured discharge (Mesa utility rate book), where evaporation is already off the sewer bill and recovery saves less. Ask whether a cooling tower meter or evaporation credit already applies at your site; if it does, the sewer saving shrinks.
  • Tower tonnage and operating hours by month
  • Your current water treatment program and who runs it
  • Any discharge limit or permit condition on the site

Blowdown volume is the ceiling on what recovery can return. If your blowdown meter is missing or unreliable, fix that first. A proposal sized on an estimate is a guess.

2. Ask what the system does with the water

Recovery systems differ in what they return and what they leave behind. Ask each vendor:

  • How much of the blowdown comes back to the tower, measured on water like yours rather than modeled
  • What is left over, how much of it, how concentrated, and where it goes: sewer, hauling or further treatment
  • What chemistry it can handle, including the limits for hardness, silica and total dissolved solids, and what pretreatment it needs above them
  • What it uses to do the work: power, membranes, chemicals and consumables

A system that returns a large share of the blowdown but leaves a concentrate your sewer authority will not accept still leaves you with a disposal problem.

3. Check how it fits the plant you have

For a retrofit, ask where the system ties in, how much floor or pad space it needs, whether the tower or the treatment program has to change, and whether installation needs a shutdown. Bring your water treatment provider into the conversation early. Recovery changes the water they are treating, and the two have to work together.

4. Price it against your own rates

Savings come from water you no longer buy and sewer charges you no longer pay, set against the system’s power, service and consumables. Use your actual tariffs, not a national average. At the first commercial water tier, water plus sewer is $7.76 per 1,000 gallons in Chandler, Arizona (Chandler rates, effective March 2026) and $21.14 in Houston (Houston Public Works, effective April 2026). The same system can pay back quickly in one place and slowly in another.

5. Make the result reportable

If the project supports a water goal, decide before installation how you will show the result:

  • Meter the recovered water separately, so gallons avoided are measured, not estimated
  • Keep the twelve month baseline from step 1 for comparison
  • Count the water behind the power the system uses, since power plants use water too (USGS)
  • Check whether the result changes your water usage effectiveness (WUE), site water divided by IT energy (The Green Grid), and how your reporting boundary treats recycled water

6. Check the rules that apply to your site

There is no single national rule for data center water. Your utility sets the terms for supply, your sewer authority sets limits on what blowdown may carry, and some states now set water conditions for new data centers: Florida’s 2026 law requires reclaimed water for a large data center’s water allocation when certain conditions are met (Florida SB 484). Recovery reduces the volume you discharge and raises its concentration, so confirm the remaining discharge still meets your limits.

Questions to put to every vendor

  1. What share of our blowdown would come back to the tower, and is that figure measured or modeled?
  2. What is left to discharge, and does it meet our sewer limits?
  3. What are your limits on hardness, silica and dissolved solids, and what happens above them?
  4. What does the system use in power and consumables per thousand gallons recovered?
  5. Does installation need a shutdown, and what changes for our treatment provider?
  6. How will we meter and report what it recovers?

Where Nona fits

Nona RECOVER is one option in this category. It treats cooling tower blowdown on site and returns it to the tower, so a site can use up to 50% less water for cooling. It does not recover water lost to evaporation. The savings calculator runs the numbers for a specific tower size and local rates, and our blowdown recovery guide explains how it works.

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