A data center is a building that must never get wet, standing in the middle of a site that is almost entirely roof, pavement, and equipment yard. This page covers the exterior half of that problem — generator and fuel aprons, chiller and cooling tower pads, transformer yards, receiving aprons — and is honest about the half we don't sell.
What a hyperscale campus does to a rainstorm
Walk a data center site and what registers first is how little of it absorbs anything. One data hall roof runs a quarter million square feet or more. Around it sit generator yards, fuel islands, chiller plants, cooling tower basins, transformer pads, security drives wide enough to turn a lowboy, and a receiving apron built for a 60,000-lb machine off a trailer. The landscape strip at the fence is usually the only pervious ground on the parcel — and it is downhill of everything.
Runoff here behaves nothing like a retail lot. Roof and pavement shed essentially all of what lands on them — a coefficient near 0.95 against 0.20–0.35 for turf — and roof volume never spreads out; it funnels into a few leader points and hits grade as a jet. One acre under a 3 in./hr design storm is about 2.85 cubic feet per second, roughly 1,280 gallons per minute — and a campus has a dozen acres of it.
The stakes are lopsided too. On most sites ponding is an annoyance; here, standing water in front of a 15 kV switchgear lineup or across the only apron a service truck can reach is an availability problem, which is why these civil packages design to a longer return-period storm than the parcel next door.
Inside the data hall is not our aisle
Let's clear this up before you spend more time here: we do not sell interior data hall drainage. Floor drainage in the white space, in the mechanical galleries, under CRAH units and CDUs, and anywhere a liquid-cooling loop can let go is an engineered stainless assembly, built to a mechanical engineer's spec and tied into leak detection. It is a submittal, not a catalog purchase, and anyone telling you a polymer concrete trench channel belongs on a raised-floor gallery is guessing.
What we do sell, in depth, is everything from the building line out to the fence: generator and fuel aprons, chiller and cooling tower pads, transformer yards, receiving aprons, fire lanes, parking, plazas, and the gatehouse. Ordinary heavy civil drainage, held to an unforgiving standard.
The wet zones on a live campus — and the answer to each
Generator yard and fuel-delivery apron
The heaviest recurring traffic lives here: monthly load exercise, service trucks, and tankers on a schedule that tightens fast during a long outage. Where layout allows, run the channel parallel to the tanker path rather than across it, ending at a collection point in the apron's low corner. In a fuel-transfer area the drain is a specified element of the spill prevention plan (SPCC, 40 CFR 112): the channel collects, while containment volume, the isolation valve, and any interceptor are engineered by others.
Transformer and switchgear yards
Most oil-filled transformer yards are crushed stone over a containment pit rather than pavement — a detail worked out against NFPA 850 and the owner's insurer, and drained from below. A slot drain in the middle of that stone is the wrong product and we will say so. Our work is at the edges: perimeter road, yard-gate apron, low points in the access drive. And inside a fenced yard, ask the electrical engineer before setting any metal grate — ground grid and step-and-touch potential are their design, not a catalog decision.
Service drives, fire lanes, gates, and the fence line
Wide pavement, heavy vehicles, no tolerance for ponding at a gate. A slider's track and a crash barrier's operator sit at grade in the path of sheet flow, so put a shallow channel just outside the gate swing, discharging away from the operator vault. At the fence line, never carry an open channel under the fabric — a continuous void beneath a secure perimeter is exactly what it exists to prevent. Cross with a basin each side and solid pipe between. Load-class reasoning for the drive: heavy traffic drainage.
Entry plaza and the accessible route
Small square footage, high visibility, hard spec: ADA 302.3 caps openings in a walking surface at 1/2 in. and requires elongated openings to run perpendicular to the dominant direction of travel. A compliant slotted or heel-safe grate in the accessible route is not optional, and far easier to get right at spec time than to swap later. See ADA and pedestrian drainage.
Ponds, underdrains, and the sitework we don't sell
Every campus has a subsurface stormwater story running under the surface one, and pretending otherwise would make this page useless. Detention and retention ponds handle release rate; bioretention cells and swales handle quality. Underdrains — perforated pipe bedded in washed stone, wrapped in geotextile — sit beneath those cells, beneath the crushed-stone substation yard, and around below-grade vaults. Where a campus has real turf, a contractor may put in a classic french drain to relieve a wet area.
All of that is contractor-installed sitework. We do not sell perforated pipe, geotextile, washed stone, detention chambers, or pond outlet structures, and nothing on this page is a french drain — a surface channel and a subsurface interceptor solve different problems and are not substitutes. What we sell is the layer that meets them: the inlets, channels, and basins that catch water before it reaches the pond. On an ancillary structure with nowhere to daylight, a dry well or pop-up emitter can close out a leader — but they are not a campus stormwater strategy and we won't sell them as one.
Reading the water before you read a catalog
Area, then flow, then outlet, then channel — most bad campus drainage reverses that order.
Start with contributing area, then convert to flow. Every run serves a catchment — a pad, an apron, a stretch of drive, plus whatever sheds onto it from uphill or from a roof. As a sanity check, 1,000 sq ft of impervious surface yields about 623 gallons per inch of rain; for a design number use our Runoff Calculator and the method in Sizing for Storms: Estimating Runoff, with the intensity your civil engineer used, not a national average. Roof water is the extreme case: 155,750 gallons per inch off a 250,000 sq ft roof arrives at a few leader points, and where one daylights onto pavement it scours the base within two or three seasons — give it a real inlet, as on our downspout drainage page.
Then size the outlet, because the outlet is the bottleneck. Running full at a 1 percent slope, a 4″ line carries roughly 110 gpm, a 6″ about 330, an 8″ about 700. If peak flow into a 200 ft run is 900 gpm, one 6″ outlet will not do it no matter how handsome the channel — you need multiple outlets, a larger line, or a mid-run basin that lets you upsize.
Check fall and velocity last. Keep outlet pipe at 1/8″–1/4″ per foot (1–2 percent) and aim for at least 2 ft/s so the line scours itself instead of silting. On a dead-flat pad — and data center pads are engineered flat — a pre-sloped channel builds fall into the invert so a long run keeps moving. Do this once in front of a drawing and you will never need a quick-selection chart.
Load class on a site where the heaviest thing arrives once
Spec against the heaviest wheel or point load that will ever cross the grate, not the daily traffic. Here the everyday vehicle is a pickup and the governing vehicle is a fuel tanker, a lowboy with a transformer on it, or a crane. That gap is where campus drainage goes wrong.
EN 1433 class → where it belongs on a campus
Class
Test load
Where it belongs here
A 15
15 kN ≈ 3,370 lbf
Entry plaza, walkways, accessible route. Pedestrian only — never where a vehicle can stray.
B 125
125 kN ≈ 28,100 lbf
Parking stalls, light service paths, landscape edges.
C 250
250 kN ≈ 56,200 lbf
Parking aisles and curbside; the floor anywhere a truck can reach.
D 400
400 kN ≈ 90,000 lbf
Service drives, fire lanes, generator and fuel aprons, gate thresholds. The campus default.
E 600
600 kN ≈ 135,000 lbf
Tanker standing areas, dock approaches, equipment set-down.
F 900
900 kN ≈ 202,000 lbf
Crane setup zones and heavy-lift pads, where an engineer calls for it.
Read that table with two cautions. EN 1433 values are test loads applied to the grate assembly, not wheel loads — a proof rating, not a truck. And the shorthand many of us grew up with, AASHTO H-20 at a 16,000-lb wheel and HS-25 at a 20,000-lb wheel, measures something different again. Use it as a trade heuristic, then confirm against the published rating and your engineer's spec. Full ratings are in our Load Class Recommendation Guide.
The load nobody accounts for is the crane. Outrigger floats on a mid-size mobile crane can put 50,000–100,000 lb through a single point, and a mat bridging a trench drain concentrates that load at the channel edge. If you know where equipment swaps stage, route the drain out of the footprint; if you can't, spec up a class and write mat placement into the lift plan.
Grate choice settles load class, safety, and theft exposure at once: ductile and cast iron for vehicular zones, steel where you want a particular bar pattern, bolt-down wherever the yard is fenced but unwatched. The material breakdown lives in our grates section and the matching sets in channel grates — start at ductile iron for the yard and work down only if traffic justifies it.
What we'd spec, zone by zone
The calls we make when a spec-stage package lands on our desk — starting points to argue with, not rules.
Heaviest recurring load · Class D–E territory · quote-only
When the governing vehicle is a loaded tanker that stops on the grate, we go to PowerDrain. S100K at 4″ nominal covers most apron perimeters; step to S200K at 8″ or S300K at 12″ when catchment or run length demands. We reach here rather than a lighter line because of the edge: this is a static-load, hard-turn environment, and the edge fails first on an underspecified channel. ACO is quoted per project, not sold from the cart — send run and load class and we will quote it.
Capacity: at Class D–E the grate open area, not the channel, often limits intake. Plan an outlet every 60–80 ft on an S200K run — one 6″ outlet caps you near 330 gpm whatever the channel size.
Filcoten's fiber-reinforced high-performance concrete is our default around evaporative plant, which leaks water on purpose — drift off the fill, basin splash, condensate, a full drain-down at maintenance. Run it as a perimeter channel so nothing migrates toward the electrical gear feeding the plant, and expect year-round wetting plus freeze-thaw at an exposed edge: conditions that punish a cheap channel. 4″ Tec V100 handles a pad perimeter; 8″ Tec V200 and 12″ Tec V300 take collector runs. It ships from stock, which matters when a contractor needs material before the next pour.
Capacity: size for the design storm across the pad footprint, not the drain-down — and confirm with the mechanical spec that blowdown is not entering this line.
Dura-Slope earns its place where the apron is long, dead flat, and has to move water to one end without a stepped subgrade — the value pick on a campus: pre-sloped, contractor-friendly, with a grate matrix running well past residential ratings. We spec it on receiving aprons, service yards, and drive-aisle intercepts where PowerDrain would be more channel than the job needs — and it is where load class gets underestimated most often, because the governing traffic happens twice a decade. With a dock face, add the detail from our loading dock drainage page: a channel at the base of the approach so water never runs at the pit. Match the grate to traffic from the Dura-Slope grate range.
Capacity: a pre-sloped run gains invert depth as it goes, so the downstream end carries more. Put the outlet at the deep end, and don't split a sloped run in the middle without thinking it through.
When one run has to take everything — a wide apron, a leader group, and a drive intercept on a single line — KlassikDrain gives you the section and the grate catalog to do it. K100/KS100 at 4″, K200/KS200 at 8″, and K300/KS300 at 12″ cover the range; the KS stainless-edge variants are what we point at when a specifier wants a hard edge in a high-cycle zone. Quote-only like all ACO — request pricing with run lengths and class.
Capacity: size outlets from calculated flow and put them on the drawing, not in the field — adding one mid-run is a change order, not a field decision.
Point collection · serviceable access · orderable online
Every channel run should end at a basin, and every paved low point deserves one. Their most valuable job isn't the storm at all — it is being where grit, tracked-out gravel, and construction fines drop out before reaching the site pipe. A lights-out campus has no grounds crew, so go a size larger than flow requires: an 18″ or 24″ basin holds a season of grit and gives a technician a lid to service alone, while 9″ and 12″ suit landscape edges. Kits bundle the common configurations, outlets and fittings and drainage fittings connect to civil pipe, and a valve box gives at-grade access to buried isolation hardware — the box is ours, the valve is your engineer's.
Capacity: basin intake is governed by grate open area, not basin volume. A 24″ basin under a half-blocked grate performs like a 9″ one — the argument for putting it where someone can reach it.
Entry plaza, gatehouse & phase-two retrofits — NDS Pro Series and narrow-profile channel
Pedestrian, light vehicle & saw-cut work · orderable online
The front of the campus is a different job: short runs, tight thresholds, a walking surface that meets ADA 302.3. The 5″ Pro Series handles the gatehouse apron and plaza edges; the family's 3″, 8″, and 12″ sizes let you match an existing depth on the inevitable phase-two cut. For door thresholds and paver details, the narrow bodies — NDS Micro, Mini, Slim, Spee-D — fit where a full trench won't. Browse by width.
Capacity: the grate is the constraint here, not flow — openings no larger than 1/2″, elongated slots perpendicular to travel. A retrofit inherits the existing outlet, so verify it has headroom before widening the channel that feeds it.
Questions from data center spec teams
What load class should a data center generator yard drain be?
Class D 400 kN is the working minimum anywhere a fuel tanker, boom truck, or loaded trailer crosses the grate; we push to Class E 600 kN in the tanker standing area and wherever a crane might set outriggers. EN 1433 values are test loads on the grate assembly, about 90,000 lbf at D 400 and 135,000 lbf at E 600, not wheel loads. AASHTO H-20 at a 16,000-lb wheel and HS-25 at a 20,000-lb wheel measure something different again, so treat any EN-to-AASHTO comparison as a trade heuristic, not a standards equivalence.
Do you sell drains for the data hall floor?
No. Drainage in the white space, the mechanical galleries, and under CRAH or CDU equipment is an engineered stainless assembly tied to leak detection, specified by the mechanical engineer and fabricated to that spec. It is a submittal, not a catalog purchase, and we do not stock it. This page is exterior campus work only.
How much water does a data center roof actually produce?
Roughly 623 gallons per 1,000 square feet for every inch of rain. A 250,000 square foot roof yields about 155,750 gallons in a 1-inch storm and sheds essentially all of it. It reaches grade at a handful of leader points instead of spreading out, which is why pavement in front of those points scours long before the yard ponds.
Can a trench drain serve as fuel or oil containment?
No. A channel collects and conveys; it does not contain. In a fuel delivery apron or an oil-filled transformer yard, the containment volume, the normally closed valve that holds a spill on site, and any separator or interceptor downstream are owned by the civil and fire protection scope. We supply the surface collection layer inside that design and nothing beyond it, and we sell no pumps, separators, or treatment equipment.
Can cooling tower blowdown go into the site storm drain?
Usually not. Evaporation alone runs about 3 gallons per minute per 100 tons of cooling, so a 5,000-ton plant sheds roughly 150 gallons per minute as vapor. Blowdown carries biocides, inhibitors, and concentrated solids, and most jurisdictions route it to sanitary sewer or a permitted discharge rather than the storm system. Size the pad drain for rainfall, drift, and splash.
How do I get pricing on ACO PowerDrain or KlassikDrain for a campus package?
Those lines are quote-only rather than cart items. Send run lengths, load class, grate material, outlet locations, and your schedule through our quote request and we come back within one business day with pricing and lead time. Attach the civil sheet if you have one.
Working a data center site package?
Send the civil sheet, the load class, and the run lengths — we'll spec the collection layer and quote it within one business day.
