This system pairs a structure with a growing method rather than selling one and leaving the other to be worked out. The tunnel gives the crop a cover that keeps heavy rain and wind off it, and the gutters inside carry a recirculating film of nutrient solution rather than soil. The two are designed together, which is what makes the slope, the reservoir and the cover match: the gutters drain at a set fall into a return manifold, the tank is sized to that volume, and the cover holds the humidity the crop works in.
A tunnel and a hydroponic system are usually bought separately, and the part that goes wrong iswhere they meet: the gutters are set at a fall that does not match the tank, the cover holds morehumidity than the crop can take, and the return line is undersized for the flow. This system isspecified as one product so those three agree.
The structure is an arch tunnel, which is the least costly way of getting a crop under cover withoutinternal columns and the easiest shape to extend in a straight line. It keeps heavy rain off the cropand reduces wind damage on the rows, which on a leafy crop is what decides whether the leaf ismarketable or marked.
Inside it the crop is grown on NFT gutters rather than in soil. The two halves of the system arequoted together, so the number of gutters, the length of the runs and the fall are settled before thetank is sized rather than after. Systems of this family sit with the rest of the hydroponics system range on this site.
The gutters are food grade PVC and are set at about 1.5 per cent fall along the run. The slope isthe part that makes NFT work: the solution has to move as a shallow film over the root rather thanpooling, and a gutter that is too flat leaves standing solution that starves the roots of air, whileone that is too steep runs past the roots before they take anything up.
Because the fall is fixed, the run length is fixed with it. Extending a run beyond the length theslope supports is what causes the far end to run short, and that is a layout decision rather thansomething that can be corrected with a bigger pump afterwards. Filtration ahead of the gutters is partof the same specification, since a partly blocked filter changes the flow at the far end first.
The set includes a 500 litre reservoir, a pump and a return manifold. The tank is sized to thevolume the gutters hold plus the working margin, and the return manifold brings the solution backrather than letting it drain away, so the water the system uses is the water the crop holds plus whatevaporates.
The cover is a PE film that holds the humidity inside the house at around 70 per cent and blocks UV.On a leafy crop that balance is what the leaf quality depends on: too dry and the leaf edges mark, toohumid and the canopy stays wet, which is where disease establishes. The cover is part of the systemrather than an accessory for that reason.
The table below is the standard system. Run length, gutter count, tank size and the cover are set to the site and to the crop.
| System type | Tunnel greenhouse with a nutrient film technique system |
| Structure | Arch tunnel frame, galvanized steel support pipes |
| Cover | PE film, UV blocking, holds about 70 per cent humidity |
| Gutters | Food grade PVC, white |
| Gutter fall | About 1.5 per cent along the run |
| Reservoir | 500 litres |
| Circulation | Pump with a return manifold |
| Water system | Recirculating; unused solution returns to the tank |
| Packing | Pre cut hoops, film rolls and channel sections |
| Crops | Lettuce, spinach, leafy vegetables, herbs and microgreens |
| Customisation | Run length, gutter count, tank size and cover set to the site |
The frame goes up on a level base first and the film is fitted, then the gutters are set to thefall and the reservoir goes in at the low end of the run. The system is filled and run before plantingso the flow at the far end of each run can be checked while the gutters are empty, and the fall isverified at that point rather than assumed from the frame.
Maintenance is the pump intake, the filters and the return line. The intake and the filter arecleaned on a short cycle, because a partly blocked filter changes the flow at the far end of a runbefore anything visible changes. The tank is topped up and tested on a routine, and the gutters arewashed through between crops so root material does not carry over.
Systems of this type are used for lettuce and leafy vegetable production on a short cycle, forspinach and salad crops under cover, and for herb and microgreen programmes where the crop is cutrather than picked. They suit a grower moving a crop off soil onto a recirculating root zone, anoperation that wants the structure and the growing system quoted as one package, and projects where thewater supply is metered or limited. A complete kit built around a timer, pump and nutrient is describedin the complete hydroponics system kit page.
Standards for structures and components are published by ASTM International. News and analysis on controlled environment production is published by VerticalFarmDaily. A system built around automatic sensing and dosing is described in the smart automated hydroponics system page.
Because the solution has to move as a shallow film rather than pool. Too flat and standing solutionstarves the roots of air; too steep and it runs past the roots before they take anything up.
Because the parts have to agree. The fall in the gutters sets the tank size, the tank size sets thereturn line, and the cover sets the humidity the canopy sits in. Quoted separately, one of those isusually worked out to suit the others after the order.
The galvanized support steel is rated for 15 to 20 years under normal growing conditions. The filmcover, the pump, the filters and the gutter set run on their own service cycles and are replaced asthey come due.
We provide a 10 year structural warranty and a 5 year anti-corrosion warranty on the galvanized steelwork. Details are set out in the contract for each project.
Send your site dimensions, the crop you plan to run and the output you are aiming for. We reply with a layout drawing and a full quotation.
