Getting Started With the Gravity Gutter System
Alex Langston 4.28.2021
Quickly becoming my personal favorite of my own, the Gravity Gutter system started as a twist on sub-irrigated raised bed gardening. Credit goes to several folks for this one, including Larry Hall, Dr. Kratky, and YouTube’s Hoocho for the system we’re discussing here. The beauty of this grow method shines in its ease, passive watering, and flexibility, though some say you may be sacrificing speed of growth to gain those benefits. A Gravity Gutter system consists of three major components: A reservoir, gutter, and containers. The biggest difference between this system and a lot of the others is plants aren’t suspended in a net cup with their roots in nutrient solution. With this method, seeds can be actually planted in containers filled with coco/perlite mix. The coco mix wicks up nutrient solution by being partially submerged in it using net cups that extend through holes in the containers and gutter.
Gutter (4” PVC pipe)
2 4” PVC caps
2” Net cups
Clay pebbles (Optional)
½ inch irrigation tubing
1 Bulkheads, Ts and valves for ½ inch tubing
1 Float valve per PVC gutter
70/30 Coco coir/perlite mix
Plastic pots with *no* drain holes at the bottom
*Quick note: Before you begin, choosing your reservoir can reduce the amount of work involved in putting together this system. Unlike NFT, there is no submersible pump to move water through your system. The Gravity Gutter system relies on… Gravity. More on that soon.
Your reservoir needs to sit above the gutters with irrigation line running between them. Gravity forces water down the irrigation line, through a float valve installed on one end of the gutter. Holes in the top of the gutter and bottom of grow containers allow net cups filled with media to dip into nutrient solution, wicking it up through the rest of the grow media. It may sound complicated, but it will all make sense after reading through the build guide below.
Drill a hole for a bulkhead as close to the bottom of your reservoir as possible. If your res is a 55 gallon drum, like mine, you’ll likely have to cut off the top of the drum. There wasn’t any way to install the bulkhead near the bottom by myself, or with the top of the drum still attached. To cut it off, I used an oscillating tool. If your res is narrow, make sure you can reach near the bottom of the drum to assemble the bulkhead. Once the bulkhead is in place, screw on the nozzle and attach the irrigation line.
Next, drill a hole for the float valve in one of the caps of your gutter. Assemble the float valve in the hole and attach your irrigation line.
*Helpful Hint: Place a T joint and an inline valve in the tubing before each float valve for every gutter. This allows for easy expansion and troubleshooting of the system, as you can shut off the flow to each gutter individually. Also place a main valve inline at the reservoir to be able to stop feeding nutrient solution to the entire system.
To allow the float valve its full range of motion, cut a long enough hole in the top of the gutter where that cap will be installed. Next, set your containers on top of the gutter in your desired configuration and drill holes for your net cups. You want the holes to go through the bottom of the container, into the gutter.
When you’ve assembled all lines and capped the gutter, after making sure everything sit right and functions properly, seal the caps in place on your gutter with pvc glue or caulk. Testing the float valve setting may be difficult before your gutter is sealed. It may also be worthwhile to caulk around the outside of the bulkhead and float valve.
Make sure the gutter is level, then set your net cups in the bottom of your containers, place the containers on the gutter so the net cups poke through, and pour in your Coco coir/perlite mix. Turn any and all valves, and you should be good to go!
As this system has only been around a while, there isn’t as much information on it out in the wild. Here are some of the bits of information I’ve picked up along the way that optimized my plants growth.
You want the level of nutrient solution in your gutter to be as high as possible. In my system, I noticed a huge difference after tweaking my float valve to allow as much solution to fill the gutter as it could. Wicking has been faster, and my coco mix stays wet. Being able to adjust your float valve through a larger hole is worth the extra exposure in the long run, if you can mitigate it.
Containers can be too big, or larger containers need more net cups dipping into the gutter. I have 27 gallon totes on one of my gutters and 3-5 gal pots on another. The two totes I’m growing in each have three net cups in the bottom. Knowing what I know now, I would’ve installed four net cups per tote.
Clay pebbles aren’t my favorite cover crop alternative. Mostly because they roll around a lot and get buried, it can make planting in phases a pain. I don’t know how I’m going to sift out all the clay pebbles when the season is over and everything has been harvested, but I’ll likely go with a hardy cover crop next round.
Caring for Plants
Something unique to the Gravity Gutter system is your plants can be direct sowed in the coco/perlite mix, just like a soil raised-bed garden. You can poke your holes, sow your seeds, and water once if necessary, then let them go (in optimal cases). After they sprout, care for them as you would any other raised bed garden. There’s little to worry about in the vein of other hydroponic systems, such as root rot, but you’ll want to monitor nutrient solution as you would with any other system. If you’re not familiar with more traditional gardening methods, this is a great way to learn while still experimenting with hydroponics.
Gravity Gutter systems are flexible. I am currently successfully growing turnips, bell peppers, hot peppers, cucumber, zucchini, cherry tomatoes, baby bok choy, basil, peas, and beans in my setup. Because you can customize and adapt your containers based on what you want to grow, there is a lot more room for experimentation. Keep in mind, though, depending on the environment your system may be more prone to evaporation. Cover your coco mix in clay pebbles or another “mulch” to help prevent evaporation until your plants form a strong enough shade cover.
Hoocho’s video with links to Larry Hall’s and Dr. Kratky’s channels: