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Fair enough. This is the response I got from Duck Duck Go assistant when I asked "How large is a closed water system for a data center?"

From the answer, it appears that the answer is "it depends."

There isn’t a single “correct” size—data centers use closed-loop cooling systems (most often closed-loop chilled water, closed-circuit evaporative/condensing water, or closed DX with refrigerant), and the required volume depends mainly on cooling capacity, configuration, and how much “thermal buffer” the system is designed to provide.

What “large” usually means in practice:

Typical closed-loop chilled-water volume (order of magnitude) Small / single-chiller plants (tens of kW to low MW): often ~1,000–10,000 gallons (4–40 m³) of system water in the loop. Mid-size data centers (several MW): commonly ~10,000–100,000 gallons (40–400 m³). Large campuses (tens of MW): can be ~100,000–500,000+ gallons (400–1,900+ m³) depending on plant design and buffer tank strategy.

How it’s determined (the key sizing knobs) Engineers estimate the loop volume primarily from: Cooling tonnage / heat load (e.g., 1 ton ≈ 12,000 BTU/hr ≈ 3.517 kW) Allowed temperature swing (how much the water temp can move while still controlling IT inlet temperatures) Design pump/pipe losses and flow rates Whether there is thermal storage (e.g., stratified tanks) which can massively increase total volume Controls/offline time requirements (how long you need water to carry load while equipment transitions) A very common conceptual relationship is:

loop volume ≈ (heat capacity needed as a buffer) / (water heat capacity × allowable ΔT) Even without numbers, that’s why volume can vary by 2–10× across facilities with similar IT load.

Quick way to sanity-check “is my system big?” If you tell me any two of the following, I can give you a much tighter estimate:

total IT load (MW) or cooling plant capacity (tons or kW) number/type of chillers (or whether it’s dry cooler / cooling towers / airside-only) target supply/return temps and the allowed ΔT (°F or °C) whether there’s a buffer tank (size, if known) approximate pipe network / lengths (optional) If you share the data center’s cooling capacity (even roughly) and the chilled-water ΔT, I’ll translate that into a reasonable closed-loop volume range.

Related search terms (for your use): closed loop chilled water volume sizing, data center chilled water system volume thermal buffer, chilled water loop sizing delta T gallons m3.