Greenhouse & Nursery Drainage

One site, six different water problems

Map each water stream before joining pipes. Greenhouse roofs collect rainfall that can often be harvested separately. Propagation and finishing aisles receive irrigation overspray, bench runoff and cleaning water. Flood floors need a controlled fill-and-return cycle. Headhouses combine media spills, washdown and equipment traffic. Fertigation and pesticide mixing rooms need spill containment as well as a decision about permitted cleaning-water disposal. Container yards receive both irrigation runoff and storms.

Reduce overspray, remove spilled media and eliminate persistent wet areas as part of pest management. Drainage helps remove breeding habitat, but it does not replace scouting, sanitation or irrigation control. UMass Extension explains the connection between wet floors, algae, fungus gnats and shore flies.

What a growing operation needs

Use point drains or catch basins where grading brings water to isolated low points, linear channels along broad runoff boundaries, and subsurface drains for water within the soil. Gutters, downspouts, tanks, pumps, controls and treatment may belong to a separate greenhouse or civil system. Drainage Connect lists collection products and pipe components; confirm the exact schedule and availability.

Emptying a flood floor on schedule

Have the cultivation-system designer set the flood depth, hold time, drainage window and allowable residual water for the crop. Return water usually belongs in a dedicated recovery system, with storage for the operating cycle, filtration, water-quality management and controls. Include pump failure, blocked return and overflow behavior in the design.

ErfGoed supplies integrated cultivation-floor water systems with matched pumps, filters and controls. This is a useful outside comparison when the project needs coordinated ebb-and-flood irrigation and water reuse; a general-purpose trench channel alone does not provide that function. The listed surface drains and pipe components are only part of that equipment scope. Site performance and supply scope still require a project proposal.

Subsurface drainage under beds, pads and field rows

A conventional French drain uses permeable aggregate and collection pipe where needed. NDS EZflow is a gravel-free alternative in the manufacturer's wider range; confirm availability and configuration. Soil permeability, water-table depth, root intrusion, filter compatibility, outlet elevation and equipment loading govern whether either approach works. Neither corrects a sealed surface that cannot admit water, and neither should become an unreviewed disposal route for nutrient or pesticide runoff.

Cleanable floors and contained chemical areas

The catalog already includes ACO sanitary stainless point and linear drainage. Consider accessible strainers and removable covers for wash areas; match floor waterproofing or resin coatings to the drain flange and seal. An isolated spill sump or a contained floor without an open drain may be the appropriate mixing-room layout. Decide collection and disposal before selecting the drain material.

Do the volume math before you open a catalog

Separate total water volume from peak collection flow. These examples use US gallons and are illustrations, not local design storms or required irrigation schedules.

Check inlet capture and bypass, channel conveyance, outlet losses, pipe size and slope, receiving water level and blockage together. A nominal 4-inch or 6-inch outlet has no single universal GPM capacity. A full-pipe Manning calculation assumes a defined internal diameter, roughness and energy slope; it does not prove that a shallow flood floor can supply enough head to sustain that flow. Multiple inlets still share the capacity limit of any common main, storage or pump.

Set floor grades from the collection layout, floor finish and traffic. A pre-sloped channel provides an internal fall while its top follows the planned surface, but no built-in slope guarantees 2 ft/s during intermittent low flow. Design removable solids capture and cleaning access rather than relying on a universal self-cleansing velocity for peat and perlite.

Use the runoff calculator and runoff sizing guide for preliminary storm checks. Interior design also needs the maximum credible simultaneous irrigation, washdown and equipment discharge; flood-floor return follows its own operating cycle.

What fertigation water does to a drain

Separate diluted crop feed, concentrated fertilizer or acid stock, sanitation washwater and accidental spills. One feed pH or nitrogen concentration cannot describe all four. List each chemical, concentration, maximum temperature, contact time, cleaning method and expected mixtures. Repair chronic dosing leaks rather than designing for a permanently flooded mixing-room floor.

• Plastic is not one material. NDS Mini Channel has a PVC body; Dura Slope uses HDPE. Grates, outlets, solvent cement and seals may differ from the body. Obtain compatibility evidence for every wetted component, including sanitation exposure; do not call the whole NDS range chemically inert.
• Concrete construction is not chemical approval. FILCOTEN is high-performance mineral concrete. Its low water absorption does not prove compatibility with concentrated acids, fertilizer stock or oxidizing cleaners. BG's material guidance also identifies chemical limitations for galvanized and stainless components. Fiber reinforcement alone does not justify selecting it for the most aggressive room.
• Polymer concrete and stainless need exposure checks too. ACO's polymer-concrete chemical chart distinguishes short and long exposure. For stainless assemblies, alloy, welds, seals and cleaners matter; ACO's cleaning and material-resistance guidance covers both metals and elastomers. A stainless grate does not protect an incompatible channel or joint.

For a cleanable wet room, compare the listed ACO stainless families against the documented exposure. For chemical storage and mixing, establish secondary containment and recovery first; a chemically resistant drain is not, by itself, a containment system.

Rating the traffic: bench cart to loaded forklift

Pedestrian aisles, loaded carts and forklift crossings need different load assessments, even within the same building.

• EN 1433 A15 — 15 kN test force. Areas used only by pedestrians and cyclists.
• EN 1433 B125 — 125 kN test force. Pedestrian areas, car parks and parking decks; verify the product and traffic.
• EN 1433 C250 — 250 kN test force. Kerb and edge-of-road locations; not a blanket truck-aisle or forklift specification.
• EN 1433 D400 — 400 kN test force. Road traffic lanes and parking areas, subject to the selected assembly and installation.
• EN 1433 E600 — 600 kN test force. Locations with high wheel loads, with project-specific design and manufacturer confirmation.
• EN 1433 F900 — 900 kN test force. Locations with exceptionally high wheel loads, with project-specific design and manufacturer confirmation.

EN 1433 class numbers state a test force in kilonewtons, not a permissible vehicle weight. NDS letter classes use separate pressure and traffic recommendations; NDS Class B does not establish EN 1433 B125. H-20, HS-25 and AASHTO M306 also require their own applicable documentation. Do not use a letter match, PSI conversion or an EN-to-AASHTO shortcut as evidence of compliance. See the load recommendation guide.

For forklifts and pallet jacks, submit laden wheel loads, tire or roller type, contact area, turning and braking, crossing frequency and direction. Check the complete channel, grate, frame, fastening, concrete support and slab joints. A metal grate upgrade does not establish forklift suitability, and recessing a grate does not remove wheel loads from it.

Where each piece goes on a growing site

Aisles: coordinate the low line and walking surface

Place a channel along a continuous low line where that limits sheet flow; use point drains or cross drains where floor grades actually lead to them. Make covers removable and secure them with the specified locking hardware. Keep cleaning access clear of benches and stored pots. Choose grate openings for cart casters and footwear as well as inlet capacity.

On routes required to be accessible, floor openings must not pass a sphere larger than 1/2 inch, and elongated openings run perpendicular to dominant travel. Surfaces must be stable, firm and slip resistant. Follow ADA surface and level-change provisions; accessible walking-surface cross slope is limited to 1:48 under section 403.3. Allow construction tolerance below that maximum. A decorative pattern, nominal load class or color does not establish compliance.

Discharge and water reuse

Keep roof runoff separate from nutrient-bearing irrigation return and chemical washwater. Relatively clean roof water may suit storage, a permitted surface outlet or infiltration following soil testing, groundwater separation, setbacks and overflow design. Pop-up emitters need sufficient driving head and a safe surface flow path; dry wells require suitable infiltration conditions. Neither treats dissolved nutrients or pesticides. Yard runoff is not automatically clean because it came from outdoors.

For irrigation return, compare lined recovery storage, filtration and managed reuse with a locally approved treatment and discharge route. Sediment capture does not remove all dissolved contaminants or disinfect recovered water. UMass water-source guidance discusses reuse and treatment. Prevent cross-connections with potable water and obtain the required backflow protection.

For pesticide mixing and loading, prevent spills from reaching storm pipes, soil or water sources; use a contained pad and managed recovery where appropriate. The EPA applicator training manual addresses this separation. Follow pesticide labels and the applicable state, local and receiving-utility requirements. Permit applicability varies by water stream and site; a nursery-wide discharge exemption or blanket permit requirement should not be assumed. EPA nursery guidance supports source reduction and leachate recovery.

Valve access in shared corridors

Keep valve boxes out of wheel paths where practical. A bolt-down lid provides retention, not a traffic upgrade: the NDS 13 × 24 Pro-Spec sheet specifies pedestrian and lawn-care-equipment loading. Use a separately documented enclosure and installation for vehicle crossings. Identify nonpotable services using the local utility or code convention; recaptured irrigation water does not automatically trigger one universal cover-color rule.

What we'd spec, zone by zone

These are starting points for selection after the flow, exposure and traffic are known. Confirm each assembly and its installation rather than treating a family name as a finished specification.

Maintenance that protects the system

Collect spilled media before washdown. Inspect after repotting, major cleaning and storms, and set a routine interval from observed buildup. Lift and clear baskets before they obstruct inlets, remove algae and roots, check loose grates and failed seals, and verify return-pump alarms and overflow routes. Recover cleaning waste through the approved route. Match flush pressure, temperature and cleaner to the drain and floor finish; do not wash trapped solids deeper into the pipe.

Related sites we drain the same way

Growing operations share more with these than with a subdivision: farm and barn drainage for equipment aisles and wash areas, yard and lawn drainage for the low-point side, garage and shop floor drainage for the headhouse, and loading dock drainage for the shipping end.