This article details the step-by-step instructions on how you can make a strawberry tower that can be used for your hydroponics/aquaponics system. The water dripping through the system contains the nutrients, so soil is not used. The growing media is expanded shale, but you could also use expanded clay or gravel.
Step 1 Marking the pipe
The first step is to place a mark on each end of the pipe, then rotate it 180 degrees and mark the other end. Then snap a line down the entire length of the pipe. You could also use a straight edge to mark a line, but I find the chalk line to be more accurate and easier. Turn the pipe over and snap a second line down the opposite side.
Step 2 Marking the pocket spacing
Along each chalk line you will place a series of marks. Starting at 2 inches, draw a mark every 8 inches. This will be the spacing between each pocket in the tower. If you are going to grow plants that need more root area, set the spaces further apart. I typically replace the strawberry plants every season. If they grow for more than one season, they can become root-bound.
Step 3 Connecting the lines
Starting at the first set of marks, draw a line from one mark and connect it to the mark on the opposite side. Then turn the pipe 180 degrees and connect the next series of marks. Continue rotating the pipe while connecting each series of marks. These lines will be used for cutting the slots in the tower.
Step 4 Cutting the pipe
Along each cut mark, carefully cut through the pipe until you reach the measured mark you placed at the chalk line. Do not cut through more than half the pipe! Rotate the pipe 180 degrees and cut the next slot. When you are done, each slot should be on the opposite side of the previous slot.
Step 5 Heating the pipe
The general area that will be heated will be an arch shape starting at one end of the slit, up about 8 inches to the back side of the neighboring slit and then back down to the other end of the slit.
- Time for some good gloves. The pipe doesn't become flexible until it is well above the boiling temperature of water. Please be careful!
- Heating PVC should be done in a well vented area. If you overheat it, it can release some nasty gases. Please be careful! Continuously move the heat around the arched area. Try to avoid heating the area below the slit to keep the pipe from bending too much.
After a few minutes, the PVC will become soft. It helps to apply a little extra heat at the each edge of the slit since this is where the sharpest bend will be.
Step 6 Shaping the pipe
Push in the PVC so it makes a concave shape in the arched area. You will want to push it in enough so that it will touch against the back wall, but not create a seal since the water will need to trickle through that area, but don't leave too big of a gap so your growing media will fall through it. When you let go of the pipe, it will usually spring back a little, leaving a gap around ¼". I found it to be very helpful to use a few spring-clamps to hold the tight bends in place while the plastic is cooling. You will want to hold the shape in place for a couple of minutes while it is cooling. It takes me about 3 1/2 minutes to completly create each pocket. When you are done, you will have some nice pockets alternating on each side of your new tower.
Step 7 Add some pocket collars
As the water flows through the tower, the surface tension in the water can cause it to flip out of the edge of the slit. To correct this, I added a collar around each pocket. With some extra pipe, cut some rings about 1 ½" wide. Then remove enough of the ring so when it's placed over the slit area, it extends just beyond the slit. Add some silicone adhesive and clamp the ring in place. Half of the ring should be placed above the slit line. Use clamps to hold it in place until it cures.
Step 8 Catching the water
If you're not going to be draining directly into a sump tank, you'll need a way to catch the water from your towers. Take a 4" cap and add a fitting to it. Drill a 7/8" hole and thread it with a ¾" tap. There are several ways of adding fittings, but I found this to be very cost effective method.
Take a ¾" NPT to barbed fitting and screw it into the tap. If it is screwed in far enough, it will be higher than the base of the cap. This work well to help any media that as fallen through from going down the drain and clogging it. This cross-section shows how the fitting is placed into the cap. Place the cap on the bottom of the tower. The bottom pocket should not be filled with anything so you can clean the base cap if necessary.
Step 9 Hanging your tower
To hang your tower, drill a couple of holes on both sides near the top and insert some S hooks. Use a wire or chain to hang it from a strong support.
Step 10 Connecting the tower drains
To connect the tower drains together, you can attach them with tubing and barbed fittings. I made some stands from scrap 3" pipe to support the bottom of the tower. Then I used a 1-1/2" pipe with holes drilled in the side to catch the water from each tower. Each pipe then drained into the main sump tank.
Step 11 Filling the pockets
Filling each pocket can be a challenge so I made a tray-type funnel to speed up the process. Take a section of pipe and do a cut down its length. Heat the entire piece so it can be flattened, then bend up the edges so it forms a V shape.
I created a cross-cut section so you could see the inside of the tower. Please note that this sample is done with black ABS so you could see the various surfaces easier. Each pocket will hold about 5 cups, or 1 liter of growing medium. This is enough space for most shallow root plants like strawberries or lettuce. For my strawberry plants, they will usually get water for 10 minutes every hour and a half.