Building a Home-sized Hydroponic Garden From PVC Pipe

Don Coan, a retired California State University professor has been experimenting with home hydroponics for nearly 30 years. Through a series of adaptions and redesigns he has developed a home hydroponic system that provides himself and his family with an adequate supply of daily fresh vegetables.

His system is built from 4” diameter PVC tubes, schedule 40 or heavy gauge. His completed hydroponic system has 16 tubes of five foot long, enough holes for from 90 to 180 plants. The size space required for the system as Don has designed it is five feet by 20 feet long.

Parts List for the Coan PVC system

1. Four 20 foot lengths of 4” diameter PVC pipe schedule 40 or heavy gauge

2. 32 end caps for 4” diameter PVC pipes

3. Two 20 foot long 1” PVC pipe

4. 20 foot 3/8” clear or black plastic flexible tubing

5. Two end caps for the 1” PVC pipe.

6. 2 connectors to connect 1” PVC to 1” flexible hose tubing.

7. Length of flexible hose such as water hose 6 foot

8. Water reservoir container, at least 50 gallon opague plastic

9. Plastic disposable cups

10. Timer with 8 on and off settings

11. 1 Little Giant 5 msp 60 hertz v.127 A 5.8 pump

12. PVC glue

13. Bathtub silicone for leaks

14. Four heavy duty clamps to secure the hose to the pvc pipe

Don builds his system of Grow tubes made of 4” PVC pipes schedule 40 or heavy gauge. This comes in 20 foot lengths. In Mexico this pipe is 4” along the entire length but many places in the US, since it is used for irrigation, one end will be flared so another pipe can be placed inside.

Step One: The first step in constructing the system is to cut each 20 foot tube into four equal length tubes. When this type of pipe is used, the flared end is cut off and the four pipes are all cut equal amounts with the remainder, usually about four foot 10 inches. The Mexican pipe is cut into four five-foot segments. Any kind of saw can be used for this. Don uses a hand hack saw, but a table saw can also be used.

Step Two: End caps. Each tube requires two end caps. One of the two end caps is drilled with a 3/8” hole in the center. This will be the overflow valve. So of the 32 caps, 16 are drilled with a center hole.

Step Three: The end caps are glued onto each end of the five foot Grow tube with PVC glue. Some people using PVC have found end caps that fit tight enough so vasoline can be used to form a seal instead of glue. This makes the system easier to clean.

Each Grow tube will have one end cap with the 3/8” drill hole in the center and one undrilled end cap.

Each Grow tube will have two 3/8” drill hole drilled one inch from the end cap. One is drilled at the top of the tube, one at the bottom. These holes should be 180 degrees apart.

Step Four: The holes need to be drilled for the plant containers. For this a 2.5” hole saw is used that fits on the end of a 3/8” drill. To assure the holes will be in a straight line make a template of string that will tape to each end of the tube, forming a straight line across the curved surface. The template will be made by tying another string every 6” to make eight holes in the grow tube, or 4” apart for smaller plants.

Steps from one to four are completed for all sixteen grow tubes. A platform for the tubes can be built, and this can be just sawhorses with two boards across. There should be room to walk around the unit because a person has to reach in past the feeder and the drain lines.

Step Five: The feeder line will flow nutrient water from the reservoir into the growing tubes. The feeder line is 1” PVC pipe drilled with 3/8” holes. These holes are drilled in line with where the Grow tubes will be placed. If the 20 foot feed line is used and 16 tubes are used they will be about 15” apart. In the feeder line the plastic hose has to be tight so it does not leak. The hose should fit tightly and if there is any leaking the hose can be further secured with silicone bathtub calking. A fitting is glued on one end to seal it off and the other end is glued with a fitting that can be used to secure the rubber hose from the pump.

Step Six: An overflow line has to be built similar to the feeder line, with 3/8” holes drilled in the same places, but this line will require two holes at each drill position placed one inch apart. One will be for the line at the bottom of the Grow tube and one will be for the overflow hole at the end of the tube. The hole at the bottom of the tube allows for drainage, complete drainage of each tube. This drained water goes back to the nutrient tank allowing for recycle. At one end of the return line a fitting is glued to seal it.

Caution: The overflow also flows back to the nutrient tank and this extra drainage should allow for excess water to not overflow the system or come out of the tops of the growing tubes. Still, there is always a possibility of overspill so the system should be set up in an area where an overspill will not damage the floor under the system. Be sure to set it up outside or in an area where the floors can take an occasional spill.

Set Up: The Grow tubes are placed on the support frame, which can be in its simpliest form, two sawhorses with two boards placed under the tubes. The Grow tubes are placed 15” apart on the support structure and then the feeder line is attached at one end, in line with the tubes. 3/8” flexible plastic tubing is inserted in the feeder line and then placed in to upper 3/8” hole in the Grow Tube. The flexible line should be tight in the feeder line and if it leaks at all it should be sealed with bathtub calking, silicone.

The return line is operated by gravity alone so it must be placed below the tubes and a 3/8” plastic line is put at the bottom of the tube top the return line and then a second 3/8” tube from the overflow hole at the end of the Grow tube to the return line. These lines should be tight and if they leak they should be secured with more bathtub calking.

Tank Setup: A tank for nutrient water should be placed under the ends of the feeder and return lines. A submersible water pump is placed in the bottom of the tank and attached to a flexible water hose one inch in diameter that also attached to the feeder line. This hose is attached to the pump with a clamp and the same type of clamp is also used to secure the hose to the feeder line.

Pump Sizing: There are many pumps on the market including a wide variety of aquarium pumps that can be used in hydroponics. All the parts should be plastic or non corrosive so that nutrient water does not build up on the moving parts. The pump must be able to pump an inch of water to a distance of about three feet.

The return line can be simply placed over the water tank, or a second hose can be attached and then put through a hole in the cover for the water tank. This return line must have its end above the water to allow the water to flow back to the tank.

The pump is pumped for about six minutes eight times a day seven times during daylight and once at night. The pump fills the growing tubes with fresh nutrient water that then slowly drains out back to the nutrient tank.

Nutrients are added to the water supply in the tank. This should be a specially formed hydroponic nutrient that is 100% soluble and includes all 13 minerals required for plants. Fertilizers designed for soil usually do not work.

Plant Containers: The system holes are each filled with plastic cups. This cup should be a size that allows for two inches of the cup to be in the system and then secured by a 2.5” diameter width holding it in the system, a cylindrical cup. These are commercially available as disposable drinking cups. Then two holes of 3/8” diameter are drilled at the bottom of each cup so they can flood and drain with water.

Substrate: A variety of growing substrates can be used inside the cups to hold the plant roots. Don uses Rockwool in the cups in his home system starting seeds in one inch rockwool and then transferring to 2.5” cubes that fit into the cups.

If a netting piece is added to the cup other granular substrates can be tried such as perlite or grow rock.

Because the cup is relatively small it will not support a large tomato plant. So a support structure is built over the growers to support tomato vines. A second support structure is used for supporting vines such as snow peas and cucumber.

This system with its capacity for 120 plants can grow much of the fresh vegetable requirements for a family.

It is not a good system for root vegetables but can be used for most salad vegetables including the lettuces, tomatoes, cucumbers, eggplant and others. It should provide fresh food for a family for at least a generation.

Don´s own system is in his side yard at his home. It is placed so it gets day long sun in Southern California so he uses his system year round. If built in a climate with a cold winter it will need to be placed indoors or in a greenhouse to be used throughout the year.