Data center water usage: what it means for a site

Why a data center uses water

Servers turn electricity into heat. The building has to move that heat outside, day and night. Water is one of the cheapest ways to do it, because evaporating water carries away a lot of heat.

Power plants that serve the grid also use water for cooling. That use is not on the site’s water bill, but it is part of the public debate.

How cooling designs differ

Cooling designs trade water against electricity.

• Evaporative cooling. Cooling towers or evaporative units lose water to the air as they work. They use the most water and often the least electricity. They also drain concentrated water, called blowdown, to the sewer.
• Closed-loop cooling. Water or coolant circulates in a sealed loop and rejects heat through dry coolers or chillers. The loop needs little makeup water once it is filled.
• Air-cooled systems. Fans and chillers reject heat to the air with little or no water. They draw more electricity, especially on hot days.
• Liquid cooling. Coolant runs to the chips or the racks. It moves heat well, but the heat still has to leave the building, through evaporative or dry equipment.

Many campuses combine designs. Some run dry for most of the year and switch to evaporative cooling in peak heat. The design choice belongs to the buyer’s mechanical engineer, and it changes what the site must supply.

Why water became a public concern

Residents, farms, and industry share the same rivers, reservoirs, and aquifers. A large new user raises fair questions. Will it strain the supply in a drought? Will it raise rates? Will it disclose how much it uses?

Those questions now come up at public hearings. Boards in North Carolina have written or discussed water-use standards in their data-center rules. See how to read a data-center moratorium and neighbors and public opposition.

What water means for choosing a site

Water system capacity. The question is not whether a water main is nearby. It is whether the provider’s supply, treatment plant, and lines can carry a new large user, and on what terms. A will-serve letter is the written start of that answer.

Reclaimed water. Some wastewater plants produce treated water suitable for cooling. A site near a reclaimed-water line may draw less on drinking water. Whether the provider offers it, in what amount, and at what quality is the provider’s answer.

Wastewater discharge. Cooling towers send blowdown to the sewer. The sewer system must accept both the volume and the chemistry. Sewer capacity can limit a site as much as water supply.

Local rules on cooling. A county or town may require disclosure of water use, favor closed-loop or dry designs, or set conditions in a permit.

Wells and streams. A site without public water may look to groundwater or a stream. State rules can apply to large withdrawals. An engineer and a water attorney confirm what applies.

What the public record shows

Public records show water and sewer lines in many areas, service boundaries, treatment plant locations, and ordinance text. They cannot show spare capacity, the provider’s willingness to serve, or the rate for a large user. We read what the record holds and mark what it does not. See what we check for water and sewer.

Who confirms it

The water and sewer provider confirms capacity and terms. The buyer’s mechanical engineer confirms how much water a given design needs. A civil engineer confirms how the site connects.

Questions

Do all data centers use a lot of water?

No. Water use depends on the cooling design and the climate. Dry and closed-loop designs use far less water and more electricity.

Can a landowner find out if water is available for a data center?

An owner can ask the provider about nearby lines and general capacity. A detailed answer usually follows a formal request that states the buyer’s expected demand.

What is blowdown?

Blowdown is water drained from a cooling tower to control the minerals that evaporation leaves behind. It goes to the sewer and counts against sewer capacity.