Indoor Soil Drip System for Cannabis (An Explainer)

As a gardener, what’s the biggest secret to making your life easier? The answer: drip irrigation. 

Setting up an indoor soil drip system eliminates the time and energy you’ll spend every day watering your plants. It also minimizes water (and nutrient) waste and encourages happy, healthy root development.

What is Drip Irrigation for Cannabis?

Drip irrigation is a top-feeding watering system that uses a hose and special drip fittings to slowly release water to each plant within your grow room. It is a watering system suitable for outdoor, indoor, and greenhouse growing. It’s also useful for both hydroponic systems as well as soil.

There are several variations on the drip irrigation format, but the fundamental component is the targeted and timely slow release of water to the base of each plant. This increases water efficiency, and when set up correctly, ensures every plant is receiving the optimum level of moisture.

You can also incorporate nutrients into your drip system, watering and feeding your plants simultaneously. Like other hydroponic systems, this means working with a large reservoir to hold the nutrient solution. Then, the drip irrigation system delivers the solution just above the roots of the plants.

Pros of a Drip Irrigation System 

• Affordable; with about a hundred dollars and an afternoon of work, you can set up a simple system from scratch
• Simple to set up, even for beginners with little to no irrigation experience
• Reduces labor and time spent watering
• Reduces water and nutrient waste

Cons of a Drip Irrigation System

• Difficult to troubleshoot
• System failure is rare but possible
• Daily monitoring is still required
• Salt builds up if the system is used for nutrients

How Often Should You Drip Feed?

The honest answer is, it depends on your system, water pressure, drip frequency, pot size, stage of growth, soil vs. hydro, and many other variables within your setup. 

Because every setup is different, you’ll want to run a few days of tests to get the system and schedule dialed in. 

The basic rule is, the longer you run the system, the less frequently you’ll have to run it. But most growers aim to water at least twice a day.

First, turn the system on, start a timer, and allow it to run until the soil is damp but not soaking wet. This will likely take at least five minutes, if not longer. Use your finger to test for dampness through to the root system. You are looking for moisture penetrating deep into the pot.

Recheck your plants at the end of the day. How damp is the soil? Again, test deep into the pot to ensure that the roots aren’t dry. Run and time the system again.

Over a few days, you’ll get a better understanding of how much water your plants require, which means how long and how frequently you’ll have to run the drip irrigation.

How to Build a Simple Gravity-fed Drip Irrigation System

The most straightforward approach to installing a new irrigation system is with a drip irrigation kit. But with a bit of time and elbow grease, DIY works just as well.

Components You’ll Need:

• Water source (large reservoir)
• Hose adaptor, filter
• ½” poly tubing (main water line)
• 5/3 mm poly tubing (feeder lines to plants)
• Dripline
• Stakes
• Line fittings (T,L, and corners, as needed)
• Control valve

Tools You’ll Need:

• Large clippers
• RTV silicone (depending on fittings)
• Measuring tape
• Hose hole puncher

Instructions for Setting up Drip Irrigation for Cannabis

1. Plan System Layout:

Long before transplanting your seedlings into their final home, you’ll want to sketch out the system, buy the parts, and set it up.

Physically lay out every plant within your grow tent. Drip irrigation is more flexible in placement than other hydroponic systems, but you’ll still need the general idea of spacing for line length and connections.

There are many workable drip irrigation schematics available online, but most place the main water line down the tent’s center, with individual tubes branching out into each pot. 

With the layout planned, you’ll have a shopping list for the number and style of each connector, as well as a rough idea of line lengths.

2. Measure and Cut:

Layout ½” poly tubing along all main water lines in your schematic. Cut into the right lengths using clippers, and place corner and “T” fittings where needed. Depending on what type of fittings you are using, you may want to use RTV silicone on the connections.

3. Install Hose Adaptor, Filter, and Control Valve:

Connect the end of the poly tubing to a large reservoir. You may need an adaptor to get the right fit and should always install a basic garden hose filter to catch any particles before they clog the tubes downstream.

Take the time to install the main control valve. Depending on how many main lines and plants you are running, you may even want to put in one valve per line to give you greater control over what gets watered and when. Larger systems may also need multiple valves to concentrate the pressure into one line at a time.

If you are not planning a gravity-fed system, you will also need to install a pressure regulator on the faucet.

4. Reservoir Placement:

Because this is a gravity-fed system, you’ll have to place your reservoir above the drip irrigators. The higher up it is, the more pressure you’ll get at the exit points. 

5. Cut and Stake into Individual Plants:

It’s time to install the thinner 5/3mm poly tubing, which connects the main water line to each plant. 

Using the irrigation hole punch, punch holes in the mainline and insert the 5/3mm poly tubing. Run the poly tubing up to the stalk of each plant you want to water. Cut to the appropriate length.

6. Install Drip Line Around Each Stalk:

Now it’s time to install the drip line, which is what will slowly and precisely water your plants around the base of the stalk.

Measure and cut 15″ lengths of drip line, which should be enough to loosely circle the stalk of each plant. Connect using a “T” fitting, which should then snap into the feeder line. Install one circle per plant.

7. Test System:

With everything connected, it’s time to test your system. Fill the reservoir with water, and open the valve. Inspect every connection for leaks. Double-check that each drip line is functioning correctly, with slow, steady drips. Adjust the system as needed.

Drip Irrigation Is Perfect for Growing Cannabis 

When you grow cannabis indoors, drip irrigation is perhaps the easiest way to save you hours wasted hand watering. When done right, your plants are watered consistently, precisely targeting the root zone. 

If you want to make your life easier and your cannabis plants happier, it’s time to install a drip irrigiation system.