Datacenter
Can a data center keep cooling during water curtailment?
Connect permitted water supply to tested cooling modes, load limits, storage deadlines and recovery evidence.
Direct answer
Yes, a data center can keep cooling during water curtailment when permitted makeup water or a tested dry heat-rejection path can carry its operating load. Using the DOE/EPA water balance, Anvilfield estimates that moving from three to six approved cycles of concentration accommodates a 20% makeup cut at unchanged evaporation and negligible drift or leaks, once the new concentration is established. Without sufficient replacement water or dry capacity, use storage to complete a timed load reduction or shutdown before water or thermal limits are reached.
On this page
What makes a cooling system dependent on water?Which water restrictions actually apply to the facility?Which operating state follows each supply condition?Can the tower or hybrid cooler run without makeup water?What temperatures limit curtailment operation?How much load can remain when makeup water is restricted?How long will backup-water storage last?Can reclaimed or trucked water replace tower makeup?Worked example: keep a 10 MW rejection duty through a water cutWhat does temporary dry operation cost?How should the curtailment sequence be tested and monitored?When can the site restore normal cooling and IT load?Curtailment worksheet and contractor scopeOpen the related tool for the calculation, checklist, or packet.
FieldOS by AnvilfieldOffline-first FieldOS for job photos, proof packets, property memory, calculations, teams, billing, and owner-ready reports.What makes a cooling system dependent on water?
A data center's closed liquid loop does not eliminate water-curtailment exposure when its outdoor heat-rejection system still consumes evaporative makeup, as the U.S. DOE's data-center cooling-water guidance shows. Trace heat from the IT equipment through air or coolant, the coil or CDU, any chiller, and the outdoor heat sink. A sealed technology loop can terminate at a water-consuming cooling tower. [S10]
Inventory keeps a loop filled; makeup replaces evaporation, blowdown, drift and leaks. A closed-circuit evaporative cooler isolates process fluid inside a coil while its spray circuit still loses water. Air-cooled and water-cooled chillers have different outdoor dependencies. [S1] [S4]
| Cooling path | Water dependence in normal operation | Curtailment option | Evidence required to credit it | Basis |
|---|---|---|---|---|
| Open tower plus water-cooled chiller | Evaporation, blowdown, drift and leakage require makeup | Accepted alternate water, storage, lower duty, or independent dry rejection | Makeup balance; chiller/tower selection; transfer test | [S1], [S8], [S10] |
| Closed-circuit evaporative fluid cooler | Process loop is closed; spray circuit consumes makeup | Selected dry mode, if fitted and capable | Model-specific dry capacity and setpoint test | [S4], [S6], [S9] |
| Hybrid HXV cooler | Wet/dry split follows selected mode and weather | Water-saving or dry operation | BAC selection and control sequence at duty and ambient | [S5] |
| Dry cooler on liquid loop | No evaporative process makeup in dry mode; service fill and leaks remain | Continue within dry capacity or reduce load | Dry-bulb selection; fluid/flow limits; proven heat balance | [S4] |
| Air-cooled chiller or air-cooled DX | No tower makeup for its heat rejection | Continue within ambient/electrical capacity | Chiller/condenser selected capacity and power at ambient | [S4], [S10] |
| Direct-to-chip CDU feeding a tower-dependent facility loop | Closed technology loop does not remove the facility makeup demand | Change facility rejection mode or reduce duty | CDU and outdoor path verified together; residual air included | [S10] plus Anvilfield system-boundary synthesis |
Include residual air cooling, humidification and other essential demands inside the facility boundary. The cooling-system overview identifies the architectures; the WUE guide establishes the reporting boundary. Annual WUE does not establish peak hourly makeup demand or outage endurance. Record withdrawal, blowdown discharge and evaporation separately.
Which water restrictions actually apply to the facility?
Start with the supplier's written allocation, effective date, applicable meter, accounting period, instantaneous flow restriction and required delivery pressure. A supplier shortage percentage describes its system; the customer's allocation establishes permitted withdrawal; the plant budget assigns part of that withdrawal to cooling. Berkeley CLEE's February 2026 California report maps the service agreements, shortage plans and water-right context behind those decisions. [S11]
California Water Code §10632(a)(3)(A), reproduced in Liberty Utilities Park Water's June 2021 plan, specifies six supplier shortage bands: up to 10%, 20%, 30%, 40%, 50%, and more than 50%. Those bands do not automatically impose the same percentage cut on every data center; use the applicable supplier plan and notice to identify customer allocations and priority uses. [S14]
List potable and reclaimed supplies separately, then identify shared sources, treatment works, pumps and power. Two pipes from one constrained source are not independent backup capacity. Allocate cooling water after other essential uses, and exclude emergency or fire reserves from usable tower storage unless the approved design expressly makes them available.
Convert the restriction into an hourly operating budget
The worked allocation is an Anvilfield estimate: 13.50 m³/h reduced 20% to 10.80 m³/h. Reconcile the hourly operating budget with the supplier's daily or other accounting period: a tank can relieve an instantaneous flow restriction without creating additional permission to withdraw water.
Assign the water-service liaison to obtain written instructions, facilities to calculate the plant allowance, and the incident commander to authorize the resulting IT action. Retain the notice, timestamp, meter boundary and superseding instructions in the event record.
Which operating state follows each supply condition?
This Anvilfield operating-state matrix connects the worked water budget to cooling action. Attach each state's IT ceiling and measured switching time; retain its required component-out capacity or record the reduced redundancy. These states are separate from utility shortage stages.
| State | Entry trigger | Makeup budget | Cooling action | Duty allowed by the water balance | Timing / redundancy acceptance | Exit / owner |
|---|---|---|---|---|---|---|
| Normal | Full example supply available | 13.50 m³/h | Tower at 3 approved cycles | 10 MW | Record baseline switching time and available standby equipment | Facilities logs baseline |
| Watch | Supplier warning or forecast deficit | Confirmed allocation unchanged | Verify inventory, treatment and dry selections; prepare IT action | Current tested duty, no untested dry capacity | Prove transfer readiness before the effective restriction | Incident commander activates Restricted when allocation changes |
| Restricted | Example 20% plant allocation cut | 10.80 m³/h | Approved transition to 6 cycles, storage bridge or load reduction | 10 MW after 6 cycles established; 8 MW at unchanged 3 cycles without storage | 6.67 h worked concentration transition; verify capacity with required equipment unavailable | Facilities verifies conductivity and balance; IT lead executes needed cap |
| Backup-only | Primary makeup unavailable | 0 primary; separately verified replacement | Draw usable tank; retain treatment; use credited dry path if present | Time-limited duty; 9.26 h at 10 MW and 6 cycles without replenishment | Transfer before the thermal limit; prove required pump availability | IT action before earliest margin expires |
| Recovery | Supply permission restored; restart and refill checks in progress | Written restored allocation, with explicit refill budget | Restore wet equipment and reserve; stage load | Only duty demonstrated at each step | Retain restrictions until inventory and required redundancy return | Operations releases Normal after recovery checks |
The incident commander activates the state; facilities executes plant changes under the written emergency operating procedure; the IT lead executes the preapproved cap or migration. Connect the MOP/SOP/EOP record to the actual power-capping sequence, including who confirms completion.
Make the load-shed trigger a time calculation
Compare remaining water endurance with verified execution time plus contingency time. Anvilfield's worked settings allow 30 minutes to execute and 30 minutes of contingency, so load action starts no later than one hour before the water limit; these are worksheet settings, not code intervals. At 6.80 m³/h net depletion, that trigger is 6.80 m³ above the already excluded reserve.
An earlier thermal limit governs first. Test a failed migration and a delayed tanker so the deadline includes a usable fallback.
Can the tower or hybrid cooler run without makeup water?
An open cooling tower does not become a rated dry cooler when its makeup valve closes. Credit a manufacturer-selected dry coil, hybrid mode or independent air-cooled path. Baltimore Aircoil's technical explanation distinguishes dry sensible rejection, governed by outdoor dry-bulb temperature, from evaporative rejection, where wet bulb governs the principal cooling potential. [S4]
BAC's HXV water-saving comparison in the table does not establish peak dry capacity. EVAPCO's eco-ATWB keeps its fan on and spray pump off in dry mode until it cannot meet the temperature setpoint. During a curtailment, inhibit automatic return to unavailable wet operation and trigger the tested load action. [S5] [S6]
| Case | Verified fact or explicit input | Result | Operating decision | Source |
|---|---|---|---|---|
| BAC HXV | Current product page: three operating modes; up to 70% water savings versus traditional fluid coolers | No universal dry MW or curtailment percentage supplied | Use selected dry duty at the required ambient and fluid temperatures | [S5], undated live page checked 2026-11-05 |
| EVAPCO eco-ATWB | Dry mode: fan on, spray pump off; wet and dry specification duties are separate | Dry rating needs flow, fluid, inlet/outlet, dry bulb and fan-power selection | If wet operation is unavailable, execute the tested cap before setpoint is lost | [S6]; [S9] Bulletin 230-E Metric 0725, PDF p. 71 |
| Dry coil screen at 30°C ambient | Anvilfield input: 35°C required fluid outlet | 5°C outlet-to-air difference | Positive difference is necessary but does not prove rated capacity | [S4] physics; Anvilfield subtraction |
| Same coil requirement at 35°C ambient | Required outlet remains 35°C | 0°C outlet-to-air difference | No positive heat-rejection duty can deliver that outlet with a finite dry sensible exchanger alone | [S4] physics; Anvilfield inference |
| Same coil requirement at 40°C ambient | Required outlet remains 35°C | Required outlet is 5°C below air | Dry sensible cooling alone cannot deliver it; mechanical refrigeration, approved warmer loop or another sink is needed | [S4] physics; Anvilfield inference |
This Anvilfield temperature screen establishes feasibility, not MW capacity; air-cooled chillers instead use compressors for temperature lift. See the adiabatic and evaporative cooling guide for the equipment distinctions.
Require a selection and a test for the dry operating point
EVAPCO Europe's eco-ATWB Bulletin 230-E, revision 0725, page 71, requests a separate dry duty when its operating conditions differ from wet duty. Use the project's selected model and regional documentation; wet certification alone supplies no installed dry MW. [S9]
Request capacity at actual fluid concentration, elevation, fan speed, coil condition and component availability, including minimum flow and power. Match the selection to synchronized measurements of ambient dry/wet bulb, fluid temperatures, flow, plant power and IT response. Retain the witnessed point separately from the accepted performance map used for hotter conditions.
Calculate dry derating by dividing selected dry duty by wet reference duty and subtracting that ratio from one. Anvilfield estimates 40% derating for worksheet inputs of 6 MW dry and 10 MW wet, both at 35°C dry bulb, 24°C wet bulb and 45/40°C entering/leaving water, with the same component availability. Enter accepted selection duties and flows at the required operating points.
Drought can coincide with high heat: include recirculated condenser air, fouling and the required component-out condition at the agreed hot-weather point. A cool-morning transfer test establishes the transition at that condition; the hot-weather selection establishes the later capacity ceiling.
What temperatures limit curtailment operation?
ASHRAE's Thermal Guidelines, fifth edition revised and expanded, recommends 18 to 27°C inlet air for Classes A1 through A4 but 18 to 22°C for the H1 high-density class. The public reference card carries copyright 2021/2024. Identify the installed equipment class in each hall; GPU density alone does not assign H1. [S3]
A recommended range is an operating target. An allowable range describes functionality under specified conditions, including humidity and elevation. Neither overrides the server manufacturer's approved configuration or exposure limits.
Put rack-inlet sensors at affected equipment and track the hottest inlet, because a room average can conceal a local limit. The thermal-envelope guide explains these boundaries.
For non-tape IT equipment, the same ASHRAE reference limits inlet-air change to 5°C within any 15-minute window and 20°C within an hour. Measure maximum-minus-minimum change within each window. Apply tighter installed-equipment limits during transfer and recovery. [S3]
Liquid supply temperature needs a separate limit. Establish it from the installed IT and CDU requirements, then include heat-exchanger approach to determine the outdoor cooler's required leaving temperature. Retain residual air loads, network equipment and condensation constraints in the same operating state. The CDU commissioning guide connects the facility and technology loops.
How much load can remain when makeup water is restricted?
The sustainable water-limited duty is the heat load whose makeup demand fits the permitted supply after approved cycles are established. DOE's live BMP 10 says many systems run at two to four cycles of concentration, while six or more can be achievable with suitable chemistry. The water-treatment lead sets the accepted maximum and transition from source analysis, equipment limits and treatment control. [S1]
At fixed evaporation, divide evaporation by cycles minus one to find blowdown, then add evaporation to find makeup. For negligible drift and leakage at steady state, B = E/(C - 1); M = E + B. EPA's WaterSense at Work §6.3, October 2012, includes drift and leaks in the complete inventory balance. [S2]
Where drift and leaks carry basin concentration, total concentrated liquid loss is E/(C - 1); deliberate blowdown is that quantity minus drift and leakage. A negative result means the assumed cycles cannot be maintained at those losses. Conductivity approximates cycles when makeup chemistry is stable; a source change requires a fresh chemistry assessment and treatment limits.
| Baseline makeup allocation remaining | Available makeup (m³/h) | Sustainable duty at 3 cycles (MW) | Duty reduction at 3 cycles | Sustainable duty at 6 approved cycles (MW) | Duty reduction at 6 cycles |
|---|---|---|---|---|---|
| 100% | 13.50 | 10 | 0% | 10 | 0% |
| 80% | 10.80 | 8 | 20% | 10 | 0% |
| 60% | 8.10 | 6 | 40% | 7.50 | 25% |
| 40% | 5.40 | 4 | 60% | 5 | 50% |
| 0% | 0 | 0 | 100% | 0 | 100% |
These Anvilfield estimates hold evaporation per MW fixed at the example's weather and heat-transfer split, without storage draw or alternate supply, and cap duty at 10 MW. Apply verified thermal, hydraulic and electrical limits too. Storage supports transient wet duty; proven dry capacity has a separate budget.
Why the three-to-six-cycle calculation matters
Anvilfield estimates that moving from three to six approved cycles reduces steady-state makeup by 20% and blowdown by 60% at fixed evaporation with negligible drift and leaks, after the target concentration has been established. DOE BMP 10 prints a 50% blowdown reduction beside its 20% makeup reduction; the balance above gives 60%, from 4.50 to 1.80 m³/h. Use the calculated flows for storage and delivery decisions. [S1] [S2]
At six cycles, the 10.80 m³/h allocation leaves no allowance for measurement uncertainty or increased evaporation. Basin-concentration drift and leaks displace deliberate blowdown until they exceed the required total liquid loss; losses beyond that point increase makeup and lower achievable cycles.
At five approved cycles, Anvilfield estimates 9.60 MW sustainable duty under that allocation, a 4% duty reduction. Record additional operating headroom as a verified supply margin or lower duty. The tower commissioning and treatment guide covers the chemistry acceptance work.
How long does it take to reach the new cycles?
Anvilfield estimates a 6.67-hour transition from three to six cycles for a well-mixed 20 m³ circulating inventory with 9 m³/h evaporation, stable makeup chemistry, negligible drift/leaks and an approved zero-blowdown interval. With volume constant, incoming dissolved solids accumulate: multiply circulating inventory by the change in cycles, then divide by evaporation. Thus t = V_loop × (C_target - C_start) / E.
| Operating point | Circulating cycles | Makeup (m³/h) | Blowdown (m³/h) | Meaning |
|---|---|---|---|---|
| Before approved transition | 3 | 13.50 | 4.50 | Existing steady state |
| Transition at hour 0 | 3 | 9 | 0 | Approved bleed pause; makeup replaces evaporation |
| Transition at hour 2.22 | 4 | 9 | 0 | Dissolved solids accumulate at constant volume |
| Transition at hour 4.44 | 5 | 9 | 0 | Treatment remains active and concentration is monitored |
| Target at hour 6.67 | 6 | 10.80 | 1.80 | Restore bleed to hold approved six-cycle steady state |
Use this concentration sequence only within the accepted treatment program, with its chemistry limits, alarms and endpoint. Keep biocide control and required circulation active; restore blowdown at the approved endpoint. The circulating 20 m³ is separate from backup storage.
During the bleed pause, 9 m³/h makeup fits within the 10.80 m³/h allowance. Keeping the original bleed while arranging the transition instead draws storage at 2.70 m³/h; subtract that draw before assigning later outage endurance.
How long will backup-water storage last?
Anvilfield estimates that 100 m³ of usable makeup storage supports 9.26 hours at constant 10.80 m³/h demand without replenishment, or 14.71 hours with a continuous permitted 4 m³/h replacement supply, before reaching the excluded reserve. Subtract transition draw before assigning endurance.
Count only pumpable water above minimum level and protected reserve. Divide usable volume by makeup demand minus reliable, permitted replenishment. For a changing interval, add inflow and subtract demand over the elapsed time: V_next = V_now + (Q_in - Q_makeup) × Δt. Update the balance whenever weather, load, cycles or supply changes.
Prove transfer rate, controls and usable level at the required component-out condition. A tanker order is a scheduled event; it is not continuous inflow. If replacement equals demand, inventory holds but does not refill.
Use a conservative operating balance alongside the central estimate. Anvilfield's allowance case credits 90 m³, raises makeup to 12 m³/h and retains only 4 m³/h reliable inflow, producing 11.25 hours of endurance and a 10.25-hour latest action start. Replace those allowance inputs with the site's measurement uncertainty and maximum credible demand.
A chilled-water tank stores cooling energy; a makeup-water tank replaces water losses. DOE's data-center guidance describes thermal storage recharged by mechanical cooling, whose recharge-water demand follows the actual rejection path. Calculate thermal endurance separately and compare it with the water deadline. [S10]
Can reclaimed or trucked water replace tower makeup?
Accepted alternate water can replace makeup when its permission, chemistry, delivery rate and timing meet the operating budget. DOE BMP 10 identifies condensate, compatible pretreated effluent and high-quality municipal recycled water as possible sources. Establish discharge compatibility as well as source quality. [S1]
Permission for makeup and permission for startup fill are separate. NYC's amended 24 RCNY §8-05(e), effective May 8, 2026, requires municipal water for commissioning/startup fill and a Department-approved alternative-source plan for nonpotable makeup. Apply the governing rules and service agreement at the actual site. [S12]
Before switching, compare hardness, alkalinity, silica, chloride, conductivity and microbiological control with the equipment and treatment program. Recalculate approved cycles and makeup for the new or blended source; poorer chemistry can erase the expected water savings. The evaporative basin and cold-plate loop have different chemistry boundaries; raw makeup does not belong in the technology loop. Put source authorization, backflow arrangement, connection, pump rate, sampling, receiving hours, access, spill controls and unloading duration into the supply scope.
Anvilfield estimates each accepted 20 m³ delivery buys 1.85 hours at 10.80 m³/h without other inflow, or 2.94 hours against a 6.80 m³/h deficit. Starting with 100 m³ usable, this schedule credits eight loads at completed unloading. Model actual continuous unloading in the site balance.
| Completed unloading (hours after event) | Usable volume before credit (m³) | Usable volume after credit (m³) | Operating result |
|---|---|---|---|
| 7 | 24.40 | 44.40 | First 20 m³ accepted before action threshold |
| 9 | 22.80 | 42.80 | Continuous demand during interval covered |
| 11 | 21.20 | 41.20 | Tank acceptance remains available |
| 13 | 19.60 | 39.60 | Same 20 m³ accepted |
| 15 | 18 | 38 | Same 20 m³ accepted |
| 17 | 16.40 | 36.40 | Same 20 m³ accepted |
| 19 | 14.80 | 34.80 | Same 20 m³ accepted |
| 21 | 13.20 | 33.20 | Final scheduled delivery |
| 23.07 | 10.80 | 10.80 | Begin the one-hour load action unless further supply is secured |
| 24 | 0.80 | 0.80 | Constant-duty volume remaining; required load action has already begun |
Start load action at hour 23.07 unless further supply is secured, then recalculate demand as load falls. Missing the hour-21 load advances that deadline to hour 21.22. A missed first delivery leaves the original zero-inflow deadline, hour 8.26.
A two-hour delivery cadence gradually consumes storage: indefinite service at this demand requires a completed 20 m³ load at least every 1.85 hours on average, plus enough buffer for delays. Regional tanker competition and shared municipal/reclaimed sources belong in the dependency register. Total contracted volume alone does not establish continuity.
Worked example: keep a 10 MW rejection duty through a water cut
The worked plant rejects 10 MW outdoors and evaporates 9 m³/h at its selected operating point. The table follows the three-cycle baseline through restricted supply, established six-cycle operation and backup-only endurance. All calculated values are Anvilfield estimates.
Start each outage case with 100 m³ actually usable after any transition draw. An earlier temperature, pressure or quality failure overrides the calculated water deadline.
| Item | Value | Basis / result |
|---|---|---|
| Outdoor heat-rejection duty | 10 MW | Anvilfield worked input, not IT load |
| Evaporation at that operating point | 9 m³/h | Anvilfield operating input |
| Initial cycles | 3 | Worked chemistry input |
| Baseline blowdown | 4.50 m³/h | 9 / (3 - 1) |
| Baseline makeup | 13.50 m³/h | 9 + 4.50 |
| Restricted allocation | 10.80 m³/h | 80% × 13.50 |
| Established, approved new cycles | 6 | Approved chemistry; see transition table |
| New blowdown | 1.80 m³/h | 9 / (6 - 1) |
| New makeup | 10.80 m³/h | 9 + 1.80 |
| Gross tank / unavailable volume | 120 / 20 m³ | Worked inputs; unavailable includes minimum level and protected reserve |
| Usable tank | 100 m³ | 120 - 20 |
| Continuous backup inflow case | 4 m³/h | Worked permitted, deliverable input |
| Net tank depletion with backup | 6.80 m³/h | 10.80 - 4 |
| Endurance with backup | 14.71 h | 100 / 6.80 |
| Endurance with no replenishment | 9.26 h | 100 / 10.80 |
| 24-hour demand at 6 cycles | 259.20 m³ | 10.80 × 24 |
| 24-hour supply with backup and usable tank | 196 m³ | 4 × 24 + 100 |
| Additional volume for 24 hours, with 4 m³/h inflow | 63.20 m³ | 259.20 - 196 |
| Additional volume for 24 hours, with no inflow | 159.20 m³ | 259.20 - 100 |
| 20 m³ deliveries with 4 m³/h backup | 4 whole loads | Round upward; verify delivery timing |
| 20 m³ deliveries without continuous backup | 8 whole loads | Round upward; verify delivery timing |
| Trigger allowance | 1 h | 0.50 h execution plus 0.50 h contingency, worked inputs |
| Latest start with 4 m³/h backup | 13.71 h after initial event | 14.71 - 1; rates held constant |
| Latest start without replenishment | 8.26 h after initial event | 9.26 - 1; rates held constant |
Method and sensitivity
Anvilfield estimates use Table 7 inputs. DOE BMP 10 and EPA WaterSense §6.3, October 2012, supply the tower water balance; Anvilfield calculates endurance from usable storage divided by net deficit. Water-limited comparisons hold evaporation per MW constant; transition time uses a well-mixed 20 m³ circulating inventory and approved zero bleed; delivery calculations subtract hourly demand and credit accepted loads at completion; refill time divides missing inventory by permitted surplus supply. Cost below multiplies additional kW, hours and the energy rate. [S1] [S2]
Use the actual weather and sensible/latent heat split to establish evaporation. ASHRAE's 2024 Cooling Towers chapter distinguishes tower thermal performance from evaporation: dry bulb can change evaporation even where wet bulb dominates thermal performance. The worked 9 m³/h is an operating input, not a universal water-per-MW factor. [S8]
Translate rejected heat into an IT ceiling by subtracting compressor and other heat entering that rejection path. For a steady electrical boundary whose remaining heat is attributable to IT, P_IT,max = Q_reject,allowed - P_compressor - P_other,path. Anvilfield estimates an 8.80 MW IT ceiling for inputs of 10 MW allowable rejection, 1 MW compressor heat and 0.20 MW other heat entering that path.
Use actual operating-point compressor power and the workload-to-cooling relationship; whole-site PUE does not allocate heat to one loop. Add parallel paths only after proving simultaneous operation, shared hydraulics, electrical headroom and required redundancy.
What does temporary dry operation cost?
Anvilfield estimates $720 per day of additional energy cost for a dry mode drawing 250 kW more than the wet reference at the same delivered cooling, operating 24 hours at $0.12/kWh. The table separates energy from other costs.
| Cost term | Worked value | Calculated amount | Basis |
|---|---|---|---|
| Extra dry-mode electrical demand | 250 kW | 6,000 kWh over 24 h | Anvilfield estimating input, same delivered cooling |
| Energy rate | $0.12/kWh | $720 per 24 h | Anvilfield estimating input, energy charge only |
| Extra demand charge | Tariff-specific | Excluded from $720 | Add only under the site's tariff and billing peak rules |
| Water/sewer savings | Meter and tariff-specific | Excluded from $720 | Separate makeup billing from credited evaporative losses |
| Tank, treatment, delivery and temporary connections | Scope-specific quotations | Excluded from $720 | Obtain scoped quotes |
Add demand charges, makeup/sewer billing, consumables and temporary works. A manufacturer's “up to” energy-saving claim does not provide the operating-point input for this comparison.
Request scoped quotations for usable tank volume, foundations or support, treatment, backflow protection, transfer connections, controls, commissioning, rental minimums, delivery and removal. Separate construction, recurring readiness and event costs.
A water-saving mode cannot carry the planned load when its additional power exceeds available capacity in the required contingency configuration.
How should the curtailment sequence be tested and monitored?
Anvilfield recommends testing before the dry season and after material changes to equipment, firmware, source water, IT density or controls. Simulate signals first, then execute controlled physical transitions under the approved MOP/EOP and abort criteria. Include makeup loss, source transfer, dry entry, low level, failed metering, an unavailable cooling component and coordinated IT capping.
Trend ambient dry/wet bulb, plant supply/return temperatures, flow, rack inlets, CDU limits, plant/IT power, tank level, makeup, blowdown, conductivity and treatment status on synchronized clocks. Set recording cadence shorter than the fastest critical transition demonstrated in the test. Retain response times and uncertainty to establish the action deadline.
For a liquid heat balance, multiply synchronized flow by the installed fluid's density, specific heat and supply/return temperature difference. Use actual glycol properties and calibrated paired sensors, then compare delivered duty with the selected capacity at the same ambient and component state. Compare thermal endurance with water endurance and act on the earlier limit.
Operating rounds and retained evidence
The worked worksheet uses a 15-minute operator balance review during stable curtailment, with continuous alarms. Shorten that interval as depletion or temperature changes accelerate. Compare meter totals over identical periods and reconcile tank-level change against inflow and demand before assigning an unexplained discrepancy to evaporation.
Failed telemetry removes the associated operating credit. Enter the preapproved conservative supply/load state until independent level or flow readings restore the evidence. Retain the supplier notice, selection, tested capacity, load cap, reserve trigger, actions and shift handover together.
CDC's January 3, 2025 cooling-tower guidance calls for disruption planning, treatment and stagnation control during intermittent operation. [S13] Under NYC's amended Chapter 8, wet standby remains operation even without heat rejection; maintain its treatment and monitoring. NYC Health requires chemistry readings at least three times weekly with no more than two consecutive days between readings, weekly bacteriological indicators, Legionella culture sampling at intervals no longer than 31 days, and qualified-person compliance inspections at least every 90 days while operating. [S7] [S12]
The amended §8-05(f)(3) also requires emergency sampling for conductivity-control failure to maintain proper cycles. These are NYC requirements. [S12]
When can the site restore normal cooling and IT load?
Ending the supplier restriction does not establish plant readiness. This Anvilfield recovery framework assigns evidence and ownership to each release decision.
| Gate | Passing evidence | Hold condition | Responsible role / basis |
|---|---|---|---|
| Supply permission | Current written allocation, effective time and separately permitted refill allowance | Restriction or accounting basis unclear | Water-service liaison; [S11] |
| Delivered supply | Pressure and flow support planned duty and refill | Insufficient flow or unstable pressure | Facilities; selected design and meter evidence |
| Water quality and treatment | Accepted source/fill permission, functioning treatment, completed required cleaning/disinfection and startup sampling schedule | Unaccepted source, unresolved stagnation or failed feed | Water-management team; [S1], [S7], [S12], [S13] |
| Equipment restoration | Correct valves, pumps, fans, alarms and minimum flows proven | Transition fault or an untested mode | Facilities and controls lead; [S6], [S9] |
| Storage reserve | Required pumpable inventory restored; refill flow and duration recorded | Missing operating inventory or no net refill at planned duty | Facilities; Anvilfield balance |
| Thermal and electrical capacity | Stepped-load test stays within accepted IT/plant limits and available power | Excursion, insufficient capacity or lost required redundancy | Facilities and IT lead; [S3] plus site test |
| Release and record | Incident commander signs state change; trends and actions retained | Open critical corrective action | Anvilfield operating framework |
Reconfirm pressure and flow, restore treatment and blowdown, and follow the installed equipment's restart instructions. NYC's Chapter 8 amendments, effective May 8, 2026, require continuous recirculation during operation and documented risk-management procedures after at least three days without circulation in any system part. Section 8-06(b) requires cleaning/disinfection before reuse after at least five days without circulation; a fully shut-down tower must be cleaned/disinfected within the 15 days before operation. [S12]
Startup procedures require a qualified-person pre-start inspection and supervision. Collect Legionella cultures three to 14 days after startup, act on results under Table 8-1, and report startup or full shutdown within five days. Full shutdown requires complete system drainage. [S7] [S12]
Anvilfield estimates 37.04 hours to replace a 100 m³ inventory deficit when restored supply is 13.50 m³/h and accepted six-cycle makeup remains 10.80 m³/h, leaving 2.70 m³/h for refill. Returning immediately to three cycles consumes the entire restored allowance and leaves no refill surplus. Keep accepted six-cycle operation, reduce duty or secure separately permitted refill water until the required inventory returns.
Restore load in pretested increments while temperatures, flow, treatment and electrical demand stay within accepted limits, including the applicable inlet-temperature change windows. End Recovery only after the required operating mode, redundancy and reserve have been demonstrated; retain unresolved corrective actions with an explicit operating restriction.
Curtailment worksheet and contractor scope
Use one record per source, one per operating mode and a timestamped decision sheet for each state change. For every item below, record the measured value, permitted or selected limit, instrument/document ID, uncertainty allowance, timestamp, responsible role and action deadline. Link supplier permission, OEM selection and test evidence.
- Identify potable, reclaimed, well, stored and delivered sources, including shared source, pump and power dependencies.
- Attach the current notice, meter boundary, accounting period, draw limit and restoration instructions; deduct essential non-cooling uses.
- Trace every heat path, including residual air and compressor heat; assign heat-duty and IT-power ceilings separately.
- Record peak-hour makeup, blowdown and evaporation estimate with weather and load; reconcile calibrated meters and conductivity.
- Attach accepted chemistry, maximum cycles, transition time and treatment response to a source change.
- Measure pumpable tank volume above cutoff and reserve; test level alarms and transfer flow.
- Attach wet/dry selections with ambient, fluid, flow and component availability; record tested duty, power and temperature limits.
- Verify load priority, cap/migration sequence, execution duration and failed-action response.
- Calculate net deficit, water endurance and thermal deadline; record required load action and latest permissible start.
- Confirm alternate-source permission for makeup versus fill, delivery timing, connection and acceptance; simulate the first missed load.
- Exercise failed makeup, transfer, meter and cooling-component responses; preserve treatment and microbial monitoring.
- Prove recovery, refill rate and duration, restored inventory, staged load and redundancy; retain trends, corrections and handover.
The contractor scope includes meter calibration, tank and transfer capacity, alternate-water connections, treatment setup, controls changes, load testing and operator handoff. Separate one-time retrofit work from recurring treatment and readiness visits. Cooling contractors planning recurring readiness visits track tower additions, removals and alterations across a service territory with PorchRocket Asset Search.
Sources checked and page reviewed by Anvilfield: 2026-11-05.
Update log: 2026-11-05: Reviewed all primary sources and calculations; clarified dry derating, drift balance, alternate-water chemistry, operating-state timing and NYC standby/startup requirements; condensed repeated calculations.
How to cite this page: Anvilfield, Can a data center keep cooling during water curtailment?, 2026, https://anvilfield.com/field-guides/datacenter/data-center-water-curtailment-cooling-plan/.
FAQ
What are data center water curtailment cooling limits?
The limit is the lowest duty supported by the permitted water budget, tested heat-rejection path, distribution system and available electrical capacity. Storage extends transient operation for a calculated duration.
How does drought cooling curtailment affect IT load?
IT load falls when available water and tested cooling modes cannot carry the heat duty. In the worked case, a 20% makeup cut preserves full duty after six approved cycles are established, but requires a 20% duty cut at unchanged three-cycle operation.
How much tower backup water is needed?
Multiply the net makeup deficit by the required operating time, then add unavailable volume and protected reserve. The worked tank has 120 m³ gross and 100 m³ usable.
What is the dry-mode derating percentage?
Anvilfield's worked 6 MW dry and 10 MW wet inputs give 40% derating. Calculate the site percentage from accepted selection duties at the stated ambient, fluid, flow and component-availability conditions in the dry-mode section.
Does liquid cooling work without utility water?
Yes, when outdoor heat rejection is dry and the closed loops remain serviceable. Liquid heat capture alone does not eliminate a tower-dependent facility loop's makeup demand.
Can increasing cycles avoid a water-related shutdown?
Yes, when accepted chemistry and the approved concentration transition bring makeup demand within supply. The water-limited derating and transition tables show the available duty and time needed; retain treatment and circulation throughout.
Can water trucks keep a data center online?
Yes, when accepted water, unloading rate and delivery timing cover the deficit. At 10.80 m³/h demand, each accepted 20 m³ load buys 1.85 hours without other inflow; delayed loads can trigger action before the contracted volume arrives.
Can a chilled-water tank replace a makeup-water tank?
It stores cooling energy rather than replacing evaporated water. Calculate its thermal endurance separately and identify how its recharge plant rejects heat.
When should operators begin shutting down or migrating load?
Begin before the earliest water or thermal limit, allowing verified execution time plus contingency. The worked water trigger allows one hour; the actual site uses its tested response duration.
When can wet cooling restart after curtailment?
Restart after applicable supply, treatment, equipment and restart checks pass, then restore load through the tested recovery sequence. End Recovery when the required inventory, operating mode and redundancy are restored.
People also ask
Sources checked
- [S1] U.S. DOE FEMP, Best Management Practice #10: Cooling Tower Management Checked 2026-11-05.
- [S2] U.S. EPA, WaterSense at Work §6.3 Cooling Towers, October 2012 Checked 2026-11-05.
- [S3] ASHRAE TC 9.9, Thermal Guidelines for Data Processing Environments, fifth edition revised and expanded, reference card, copyright 2021/2024 Checked 2026-11-05.
- [S4] Baltimore Aircoil Company, Air Cooled and Water Cooled: Adiabatic and Hybrid Cooling Checked 2026-11-05.
- [S5] Baltimore Aircoil Company, HXV Hybrid Cooler Checked 2026-11-05.
- [S6] EVAPCO, eco-ATWB Closed Circuit Cooler Checked 2026-11-05.
- [S7] NYC Health, Cooling Towers: Inspection and Disinfection Checked 2026-11-05.
- [S8] ASHRAE Handbook, 2024 HVAC Systems and Equipment, chapter 40, Cooling Towers, SI online edition Checked 2026-11-05.
- [S9] EVAPCO Europe, eco-ATWB Bulletin 230-E, metric, supplied file revision 0725 Checked 2026-11-05.
- [S10] U.S. DOE FEMP, Cooling Water Efficiency Opportunities for Federal Data Centers Checked 2026-11-05.
- [S11] UC Berkeley Center for Law, Energy & the Environment, Regulating Data Center Water Use in California, February 2026 Checked 2026-11-05.
- [S12] NYC DOHMH, adopted Chapter 8 amendments, published April 8, 2026; effective May 8, 2026 Checked 2026-11-05.
- [S13] CDC, Controlling Legionella in Cooling Towers, January 3, 2025 Checked 2026-11-05.
- [S14] Liberty Utilities Park Water, 2020 Urban Water Management Plan, June 2021, p. 8-8 (PDF p. 147), filed with CPUC November 2, 2023 Checked 2026-11-05.