Gardening resources > Houseplants > Horizontal hydroponic unit plans
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Cornell gardening resources Horizontal hydroponic unit plans

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Topics on this page:
General Information
Tools You Will Need
Materials You Will Need
Adding the feed line
and feed tubes
Preparing the catchment tank

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Excerpted and adapted from Grow with the Flow, by Philson A.A. Warner, Donald A. Rakow and Charles Mazza. David Hillman, Robert McBride and Wayne Torgenson helped write this section.
Horizontal hydroponic unit under grow light stand
Click for larger view

Photos courtesy Jim Grefig

Jim Grefig, a Master Gardener involved with the School Gardening Mentor Program in Westchester County, coupled a PVC grow-light stand with a horizontal hydroponic system (pictured left) from the Cornell Cooperative Extension publication Grow with the Flow.

Below is an excerpt from the publication detailing how to build the unit.

General Information

The horizontal hydroponic unit (
Figure 1) is constructed of 1 1/2-inch PVC pipe connectors, 1 1/2-inch PVC fittings (T sections and 90 elbows), 1/2-inch ABS feed line, spaghetti (feed) tubing, and emitters.

Figure 1
Figure 1 (click for larger view)

The T sections and two 90 elbows are connected with short lengths of PVC pipe to construct a U-shaped unit that lies horizontally on a surface. The openings of each T section (a) are positioned vertically (upward) to become the grow ports in which plants will be set to grow.

Two 90 elbows (b) attached to each end of the U-shaped unit and positioned vertically (downward) connect the unit to a catchment tank. The feed line (c) is fastened to one leg of the U-shaped unit. Spaghetti tubes (d) run from the feed line to the grow ports.

The unit is suspended from a simple plant light stand (e) using light chain and S hooks and attached to a pump (t), which sits on the covered catchment tank (g). [Note: Grefig's variation uses a light stand constructed from PVC pipe.] Liquid is pumped from the catchment tank through the feed line and feeder tubes to each plant. Liquid returns through the unit to the tank by gravity.

Before beginning, read all the directions thoroughly to understand fully the construction approach.


Tools You Will Need

  • a miter box, to make straight cuts
  • a hack saw, with a 24- or 32-teeth-per-inch blade
  • a pen or utility knife
  • a commercial hole punch, a #20 nail, or an ice pick
  • an electric drill with a 3/8-inch bit
  • two 3-inch or 4-inch C-clamps
  • a ruler or a tape measure

Materials You Will Need
For U-shaped unit:
  • a 75-inch length of 1 l/2-inch PVC pipe, cut to the following dimensions:
    • one 9-inch connector
    • one 3-inch connector
    • one 2 l/2-inch connector
    • ten 6-inch connectors
  • the following 1 1/2-inch PVC fittings:
    • ten T sections
    • four 90 elbows
  • one small can of PVC pipe cleaner
  • one small can of PVC solvent-cement
For feed line and pumping system:
  • 6 feet of 1/2-inch ABS pipe
  • fine sandpaper (120 to 150 grit)
  • ten barb connectors (small plastic fittings to connect the spaghetti feed tubes to the ABS pipe)
  • ten 18-inch lengths of spaghetti tubing
  • one 5/8-inch x 1 l/2-inch bolt or dowel (to plug one end of the ABS feed line)
  • one tube of general purpose silicone glue and seal
  • one mini hose clamp (to fasten bolt or dowel in place)
  • one roll of electrical tape
  • twenty l/2-gallon-per-hour emitters (ten for unit assembly and ten for future replacement)
  • ten plastic stabilizer pegs or paper clips
  • one catchment tank -- 16 inches long, ll inches wide, 7 inches deep -- with cover (Rubbermaid Rough Tote Keeper, 3 gallon, model no, 2213, or equivalent)
  • one pump, rated 200 gallons per hour, preferably nonsubmersible, such as a fish tank pump (Supreme Aquamaster Power Filter Pump, model PLSW, or equivalent)
To attach unit to the plant light stand:
  • four 18-inch lengths of light chain
  • eight 1/2-inch S hooks
  • two 3/8-inch x 2-inch threaded eye bolts, each with 2 nuts and 2 flat washers


  1. Cut the 75-inch length of PVC pipe into the lengths specified in the list of materials as follows:

    Fasten the miter box to the work surface with a C-clamp. Using a second C-clamp, secure the PVC pipe in the miter box to ensure a square cut. Using the hack saw and the 90 cutting guides on the miter box, cut all connectors and lengths to the dimensions specified.

    Other cutting methods may be employed. Miter boxes with attached tubular saws that have replaceable blades can be used if a fine-tooth blade (like that of a hack saw) can be obtained. Powers saws, such as a radial arm saw, should be used only by adults knowledgeable in tool operation and blade selection.

    Once cutting is complete, carefully use a pen knife to remove burrs on the inside and outside edges of the cut pipe.

  2. Referring to Figure 2, lay out the elbows, T sections, and PVC pipe connectors on a flat surface.

    Figure 2
    Figure 2 (click for larger view)

  3. Assemble the unit without cement to make sure all the parts fit correctly and to establish the proper orientation of all the fittings. When inserting a connector into a fitting, the connector should fit inside about onethird to halfway.

    Note: Be sure that the openings of the T sections are perfectly upright; these will be the grow ports for the plants. The two elbow fittings that attach the ends of the U-shaped unit to the catchment tank must be oriented downward.

  4. When the unit is assembled without cement and all the fittings are properly oriented, draw alignment marks on the pipe connector pieces and their adjoining fittings and number (or letter) each fitting and pipe connector joint. These marks will ensure the proper placement and realignment of all components when the unit is reassembled with PVC solvent-cement.

  5. Disassemble the unit, then begin to reassemble it permanently using the PVC pipe cleaner and PVC solvent-cement as follows:

    1. Work on one joint at a time. You'll need to work quickly, as PVC solvent-cement sets in about 30 seconds.

    2. Apply PVC pipe cleaner to the outside surface of the pipe connector and the inside surface of the fitting. Allow the surfaces to dry.

    3. Apply PVC solvent-cement to the outside surface of the pipe connector and the inside surface of the fitting. With the alignment marks on the pipe connector and the fitting oriented 90 apart, insert the connector into the fitting until it is snug (as in assembling the joints without cement), simultaneously twisting the pipe 90 until the two alignment marks match. Do this quickly, as you have only about 30 seconds before the solvent-cement sets.

  6. When the unit has been permanently cemented together, allow the PVC solvent?cement to cure for about 3 hours.

    Note: Caution must be exercised when working with PVC pipe cleaner and PVC solvent-cement. Wear eye protection and appropriate clothing to prevent contact with eyes and skin. These chemicals are volatile and noxious and must be used in a well-ventilated area. Return the covers/applicators of these substances to their respective containers and seal them after each use to keep fumes to a minimum. Read and observe all manufacturer's warnings and directions for use.


Adding the feed line and feed tubes

  1. Place the U-shaped unit on a flat surface in its proper horizontal position. Place the 1/2-inch ABS feed line parallel to one side of the hydroponic unit (Figure 3) so that one end of the feed line is even with the base of the U and the other extends beyond the two open ends of the unit.

    Figure 3
    Figure 3 (click for larger view)

  2. Mark the feed line at intervals that align with the grow ports in the unit. These locations are where the barb connectors (and then the spaghetti feed tubes) will be inserted. It is not critical to measure the intervals exactly -- the flexibility of the spaghetti feed tubes allows for a great deal of tolerance (Figure 4).

    Figure 4
    Figure 4 (click for larger view)

  3. Lay the ABS feed line on a solid, flat surface. Using either a commercial hole punch, a #20 nail, or an ice pick, puncture holes at the locations marked on the pipe. (Do not drill holes. A rough, punctured hole holds the barb connector more firmly in place.) Using fine sandpaper, sand and clean the area around each hole. This will ensure proper bonding and sealing with silicone glue in later steps.

  4. Insert a barb connector into each hole and attach an 18-inch length of spaghetti tube to each barb connector.

  5. Plug the end of the ABS feed line that is aligned with the base of the U-shaped unit with the 5/8-inch bolt or dowel. To ensure a watertight seal, apply a coating of the silicone glue and seal around the bolt or dowel, insert it into the end of the pipe, and clamp it in place using the mini hose clamp.

    Note: To ensure a proper seal, be sure to use a silicone glue and seal product, not just silicone.

  6. Attach the ABS feed line to the outside of the U-shaped unit using electrical tape at several locations.

  7. Seal each barb connector using the silicone glue and seal. (To ensure a proper seal, be sure to use a silicone glue and seal product, not just silicone.) Allow the glue and seal to cure for 24 hours.

  8. After the glue and seal has cured, trim each spaghetti tube to an appropriate length to reach a grow port. Attach an emitter to the end of each tube.

    Note: Do not cut the tubes too short. As the unit is maintained throughout the growing cycle, it will be necessary to remove and replace the emitters. The ends of the tubes will become stretched, making it necessary to trim the tubes.

  9. Use a plastic stabilizer peg or a clip fashioned from a paper clip to hold each emitter in place. Secure the peg or clip to the spaghetti tube just above the emitter and insert it into the rock wool plug in the grow port.

  10. Attach the completed unit to the plant light stand using the light chain and S-hooks. See Low-Cost Grow-Light Frame Plans.

Preparing the catchment tank

  1. Your catchment tank should hold approximately 3 gallons. (A Rubbermaid Rough Tote Keeper works well. It also comes with a cover, which supports the pump and reduces evaporation. If the container available does not have a cover, you can construct one from 1/4-inch plywood.)

  2. Place the catchment tank at the open ends of the U-shaped unit (where the elbow fittings point vertically downward for drainage) outside the upright of the plant light stand.

  3. Position the elbow fittings on top of the catchment tank cover and trace around each fitting. Remove the tank cover and carefully cut along the traced lines using a utility knife, creating two holes for the elbow outlets. Place the tank and cover in place so that the elbow fittings fit through the cover.

  4. With the catchment tank in place, align the open end of the ABS feed line so it extends over the tank cover. At the outside edge of the cover aligned with the feed line, trace a 2 1/2-inch hole. This opening will accommodate the intake of the pump, which will sit on the tank cover. Remove the tank cover and carefully cut along the traced line using a utility knife.

    Note: The placement and size of the hole in the catchment tank cover may vary depending on the size and configuration of the pump used. If a submersible pump is used, the hole in the cover will need to be just large enough for the ABS feed line to connect to the pump outlet. A 3-gallon catchment tank, however, will accommodate only a very small submersible pump.

  5. Replace the tank cover and insert the pump intake through the cover. Trim the end of the ABS feed line so it fits into the pump outlet. Connect the pump to the feed line. If a straight connection is not possible, use a short length of flexible tubing and two mini clamps to complete the connection.

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