NFT Greenhouse Channel System

At a Glance

How This System Works

This large-scale NFT system is designed for a greenhouse, garage, or covered patio where you have room for a 4-by-8-foot growing footprint. Six 8-foot channels sit side by side on a sturdy frame, each tilted slightly so nutrient solution flows from the high end to the low end by gravity. A submersible pump in a large reservoir at the drain end pushes solution through a supply manifold to all six channels simultaneously.

With 6 plant sites per channel, this system supports 36 plants — enough to produce a serious volume of salad greens, herbs, and strawberries. At full production, you can harvest 2 to 4 heads of lettuce per week while always having new plants coming up behind them.

Why greenhouse or garage? A system this size needs a climate-controlled or sheltered environment. In a greenhouse, natural sunlight handles your lighting needs. In a garage, you will need supplemental grow lights. Either way, the enclosed space protects the system from wind, rain, and extreme temperature swings that could disrupt the delicate nutrient film.

Why this is rated Advanced: Managing 6 channels and 36 plants requires careful attention to flow balancing, nutrient management, and crop rotation. A pump failure affects all 36 plants within hours. You need a reliable pump, a backup plan, and the discipline to monitor the system regularly.

Materials List

Our philosophy: Use what you already have. Hydroponics does not require store-bought equipment. People around the world grow food this way using recycled containers, scraps of fabric, and seeds saved from last season's harvest. The links below are for convenience if you prefer to purchase, but we encourage you to improvise with what is available to you.

This page contains affiliate links. If you purchase through them, we may earn a small commission at no extra cost to you. Learn more

Frame

The channels need a sturdy support structure. Build a frame from:

• 8x 8-foot 2x4 lumber studs (for the long rails and cross supports)
• 4x 4-foot 2x4 lumber studs (for the legs and end supports)
• Deck screws (2.5 inch and 3 inch)
• 4x adjustable furniture leveling feet (to fine-tune the slope on uneven floors)

Use what you have: Any sturdy shelf, table, or even cinder blocks and a board will work as a frame. Old bookshelves are perfect. If you prefer to buy a ready-made option, a heavy-duty wire shelving unit rated for 400+ lbs can serve as the frame. Set the channels on the shelf surface and shim one end to create the slope.

Channels

Six 8-foot NFT channels:

Use what you have: NFT channels can be built from PVC fence posts, rain gutters, or even halved PVC pipe with end caps. It takes more work but costs almost nothing. Six 8-foot lengths of 4-inch square PVC fence post work well. Cut 6 evenly spaced 3-inch holes in the top of each channel (every 12 inches, starting 8 inches from each end). If you prefer pre-made channels, pick up a set of NFT hydroponic channels (4-pack with lids and net cups).

Reservoir

A large reservoir is critical for a system this size. Use a 27 to 30 gallon storage tote or a food-grade 30-gallon drum.

Use what you have: Any opaque plastic container will do. An old storage bin, bucket, or cooler works fine. Just block light to prevent algae. For 36 plants, aim for at least 25 gallons of working volume. Larger reservoirs are more stable, since pH and EC swing less between top-offs. If you need to buy one, grab a 10-gallon dark storage tote or larger.

Net Cups

3-inch net cups for all 36 plant sites:

Use what you have: Cut the bottom off small plastic cups and poke drainage holes. They work the same way. If you want the real thing, here are 3-inch net cups (25-pack).

Pump & Plumbing

• 1x submersible water pump (260–400 GPH, adjustable flow strongly recommended)
• 25 ft of 1/2-inch vinyl tubing
• 1x 6-port PVC manifold (build from 1/2-inch PVC pipe, tees, and ball valves)
• 6x short drain tubes (8–12 inches each)
• 6x 90-degree elbow fittings
• PVC primer and cement
• Teflon tape
• Zip ties and cable clips

Aeration (recommended for large reservoir)

An air pump keeps the reservoir oxygenated between recirculation cycles.

Use what you have: Check thrift stores for old aquarium pumps. They show up regularly and work great. If you need a new one, pick up an aquarium air pump.

For air stones, bare airline tubing with holes poked in it works, though air stones produce finer bubbles. You can buy cylinder air stones (4-pack) if you prefer.

For tubing, reuse tubing from old aquarium equipment if you have any. Otherwise, an airline tubing kit with check valves has everything you need.

Growing Supplies

Use what you have: A small piece of sponge or cotton ball holds a seed until it sprouts. You can also transplant seedlings from your garden. If you want purpose-made plugs, try Rapid Rooter plugs (50-pack).

Nutrients are one item you do need to purchase. Plants in water need dissolved nutrients, and there is no DIY substitute. A single set lasts months. We recommend the General Hydroponics Flora Series (3-part kit).

Monitoring & Timing

Use what you have: pH test strips from a pet store or pool supply section work fine for getting started. For more precision, a digital pH and TDS meter kit is worth the investment.

For timing, you can manually switch the pump on and off, or check thrift stores for timers. A programmable outlet timer makes life easier.

Lighting (for garage or indoor setups)

If you do not have natural greenhouse light, you will need multiple grow lights.

Use what you have: A sunny window or basic 4000K LED shop lights from a hardware store will do the job. If you want purpose-built grow lights, look at full-spectrum 4 ft LED grow lights. For a 4x8-foot area, plan on 3 to 4 lights mounted 12 to 18 inches above the channel tops.

Tools

• Circular saw or miter saw (for frame lumber)
• Drill with standard bit set
• Hole saw (3-inch) if building DIY channels. You can trace and cut with a box cutter or utility knife instead. If you need one, here is a 3-inch hole saw.
• Level (4-foot preferred)
• Measuring tape, pencil, safety glasses

Additional Materials (no affiliate link)

• Hydroton clay pebbles, to fill net cups
• Foam collar inserts, to block light around net cups
• Waterproof liner or plastic sheeting, to protect the floor under the system
• Food-grade silicone sealant, for any joints that seep

Build Instructions

Step 1: Build the Support Frame

Construct a simple table-style frame from 2x4 lumber:

• Cut 4 legs at 30–34 inches tall (a comfortable working height)
• Build two rectangular end frames (48 inches wide x 30 inches tall)
• Connect the end frames with four 8-foot long rails (two on each side)
• Add 3 cross supports evenly spaced along the 8-foot span for rigidity
• Attach adjustable leveling feet to the bottom of each leg
• The frame should support at least 200 lbs when fully loaded

Critical: The frame must slope from the inlet end to the drain end. Adjust the leveling feet so the inlet end is 1.5 to 2 inches higher than the drain end across the 8-foot length.

Step 2: Prepare the Channels

For pre-made channels, verify all holes are clean and properly spaced. For DIY PVC channels:

• Cut six 96-inch (8-foot) lengths of 4-inch square PVC fence post
• Mark 6 holes per channel, evenly spaced at 12-inch intervals
• Cut 3-inch holes with a hole saw and sand all edges smooth
• Glue end caps on both ends of each channel with PVC cement
• Drill a 1/2-inch inlet hole at the high end (through the end cap, near the top)
• Drill a 1/2-inch drain hole at the low end (through the end cap, at the bottom)
• Allow PVC cement to cure for 24 hours

Step 3: Build the Supply Manifold

A proper manifold ensures even flow distribution to all 6 channels:

• Build from 1/2-inch PVC pipe and tee fittings
• Include a ball valve on each of the 6 output lines so you can fine-tune flow to individual channels
• The manifold connects to the pump via a single supply line
• Mount the manifold at the inlet end of the frame, above the channels

Step 4: Place Channels on the Frame

• Lay all 6 channels side by side on the frame, spaced about 4 inches apart
• Secure each channel to the frame with pipe straps or zip ties
• Verify the slope using a level — each channel should drop 1.5 to 2 inches over 8 feet

Step 5: Set Up the Reservoir

• Place the 27–30 gallon reservoir on the floor at the drain end of the frame
• Install the submersible pump and air stone inside the reservoir
• Route power cords with drip loops before plugging into a GFCI outlet

Step 6: Connect All Plumbing

Supply side:

• Run 1/2-inch tubing from the pump up to the manifold at the inlet end
• Connect the manifold's 6 output lines to each channel's inlet hole
• Secure all tubing with cable clips along the frame

Drain side:

• Attach 8–12 inch drain tubes to each channel's drain hole
• Use 90-degree elbows to direct flow downward into the reservoir
• Arrange drain lines so they do not splash — submerge the ends just below the reservoir water line

Step 7: Extended Leak Test

This system moves a lot of water. Run a thorough test:

• Fill the reservoir with plain water (25+ gallons)
• Turn on the pump and run for at least 2 hours
• Walk around the entire system and check every connection, end cap, and channel seam
• Verify each of the 6 channels has an even, thin film of flowing water
• Use the ball valves on the manifold to balance flow across all channels
• Check the reservoir level after 2 hours — a significant drop means a leak somewhere

Step 8: Mix Nutrients

• Drain test water and refill with fresh water
• Mix hydroponic nutrients:
  • Target EC: 0.8–1.4 mS/cm for leafy greens and herbs
  • Target EC: 1.0–1.6 mS/cm for strawberry channels
  • Target pH: 5.5–6.5
• Turn on the air pump to keep the reservoir oxygenated
• Run for 1 hour and re-check pH

Step 9: Install Lighting (if not using greenhouse sunlight)

For garage or indoor setups, mount 3–4 four-foot LED grow lights above the channels:

• Space lights evenly across the 4-foot width
• Hang 12–18 inches above the channel tops
• Set timers for 16 hours on and 8 hours off

In a greenhouse, natural light is sufficient in spring through fall. In winter or low-light months, supplement with 1–2 grow lights.

Step 10: Plant and Commission

• Start seedlings in rapid rooter plugs 10–14 days before system commissioning
• Place seedling plugs in net cups with hydroton
• Insert net cups into channels — consider grouping crops by type (all lettuce in channels 1–3, herbs in channel 4, strawberries in channels 5–6)
• Add foam collars around each net cup
• Run final checks: pump flowing to all 6 channels, air pump running, lights on timer

Nutrient Guide

Large system note: With 36 plants consuming nutrients, your EC will drop noticeably between reservoir changes. Check levels every 2 days and top off with half-strength nutrient solution rather than plain water when EC drops below target.

Crop Suggestions

Estimated Cost

Tips & Troubleshooting

General tips:

• In a greenhouse, monitor temperature closely. Nutrient solution above 75 degrees F can cause root rot and reduce dissolved oxygen. Use shade cloth in summer.
• Always have a spare pump on hand. With 36 plants depending on continuous flow, a pump failure is an emergency.
• Stagger your plantings across channels. Plant channel 1 in week 1, channel 2 in week 2, and so on. This ensures continuous harvests rather than one large harvest followed by nothing.
• A 6-port manifold with individual ball valves is worth the extra effort. It lets you shut off one channel for cleaning without stopping flow to the others.

Maintenance Schedule

Daily

• Visual inspection: pump running, all 6 channels flowing, no wilting
• Check greenhouse temperature and ventilation
• Look for pests — greenhouse environments attract aphids and whiteflies

Every 2 Days

• Check pH and EC — a 36-plant system consumes nutrients quickly
• Top off reservoir — expect to add 2–4 gallons between full changes
• Inspect channel flow for root blockages, especially in mature channels

Weekly

• Clean pump intake screen — essential for a system moving this much water
• Balance manifold flow — check that all channels still have even film thickness
• Harvest mature crops and transplant new seedlings
• Inspect air stone — clean if mineral deposits reduce bubble output

Every 2 Weeks

• Full reservoir change — dump, scrub, and refill with fresh nutrient solution
• Trim overgrown roots in all channels
• Deep clean 1–2 channels (rotate which channels you clean each cycle)

Monthly

• Flush entire system with plain water and dilute hydrogen peroxide
• Inspect frame for stability, tighten screws, check leveling feet
• Clean or replace pump and air stone
• Inspect all tubing for mineral buildup, kinks, or cracks
• In a greenhouse: clean glazing for maximum light transmission

Frequently Asked Questions

How much space do I need for a 6-channel NFT greenhouse system?

The system itself occupies a 4-by-8-foot footprint for the growing frame, but you should plan for at least 6 by 10 feet of total floor space to allow comfortable access on all sides for planting, harvesting, and maintenance. The reservoir sits at one end of the frame and adds about 2 feet of length. A standard 8-by-12-foot hobby greenhouse can comfortably house this system with room to spare for walking and working.

Can I build this NFT system in a garage instead of a greenhouse?

Yes, a garage is a viable location as long as you provide adequate grow lighting and climate control. You will need three to four 4-foot LED grow lights mounted 12 to 18 inches above the channels, set on timers for 16 hours of light per day. The main challenge in a garage is temperature management, since garages can get very hot in summer and very cold in winter, so insulation and a space heater or fan may be necessary to keep the nutrient solution between 65 and 75 degrees Fahrenheit.

How often do I need to change the nutrient solution in a 36-plant system?

With 36 plants actively consuming nutrients, you should perform a full reservoir change every two weeks. Between changes, check the pH and EC every two days and top off with half-strength nutrient solution rather than plain water, since the high plant count causes EC to drop noticeably between checks. A 27 to 30 gallon reservoir provides enough buffer to keep chemistry relatively stable between top-offs.

What pump size do I need for a 6-channel greenhouse NFT system?

You need a submersible pump rated for at least 260 to 400 gallons per hour with adjustable flow control. The pump must push water through a 6-port manifold and supply an even thin film to each channel simultaneously, so a higher GPH rating ensures adequate pressure at every outlet. Installing individual ball valves on each manifold port allows you to fine-tune the flow to each channel independently, which is essential for maintaining an even nutrient film across all six channels.