Automatic Watering System For Growing Marijuana

Cannabis plants need adequate hydration to thrive and achieve maximum yield. When grown in an ideal environment, you’ll see just how thirsty they can get. Your cannabis plants need water and naturally consume a lot of it –  especially photos. Remember, they’re made of 80% water!

Keeping cannabis plants properly hydrated in optimal growing conditions can be a challenging and time-consuming task. Often, plants grown in pots require daily hydration, which can be a chore. This is where an automatic watering system for growing marijuana can make a big difference.

What is an automatic watering system?

An automatic or automated watering system, also called a self-watering system, is designed to keep your plants hydrated without manual intervention. They provide hydration (H2O & O2) to the plant’s roots as needed, based on a set schedule, moisture sensor, wick, or gravity feed.     

This technology is especially helpful when you have a large garden or canopy to maintain or want something else to deliver hydration (with or without nutrients) to your plants.

These irrigation systems have many names and methods of delivery, such as hydroponics, aeroponics, ebb and flow, nutrient-film technique (NFT), deep water culture, drip irrigation, sub-irrigation, aqua mats, autopots, blumats, octobubblers, and self-watering pots. Not sure which one to choose?

Read this autopot forum thread or our best pots for growing cannabis guide for help choosing the correct pots.

Automatic watering systems work well for plants needing consistent watering. Delivering consistent hydration to your plants is fundamental to generating above-average yields; however, it must be the correct amounts. That’s why one of the primary advantages of an automatic watering system for growing marijuana is its ability to regularly deliver water to the plant’s roots without drowning them. 

Proper watering is essential for cannabis. Consistently under-watering your plants can result in stunted growth and poor yield, while over-watering will drown the roots, ruin soil biology and kill cannabis plants. If you aren’t using an automatic watering system, read our guide to understand the best time to water weed plants and avoid these costly mistakes!

Components of an automated watering system 

You’ll need the following materials to build an automatic irrigation setup for cannabis plants (in any environment):  

Components of an Automated Watering System for cannabis plants
Components of an Automated Watering System

A Water Reservoir

This can be as simple as a plastic container or bucket for a couple of plants or as large as a 55-gallon drum – even for home grows. There are even 200-gallon reinforced reservoirs for larger commercial grows. Some fertilization systems are piped to existing structural water lines and drip fertilizer directly into outgoing water. 

A water pump

Most small to medium-sized systems use a submersible pump to move water to plants through drip tubing. Larger systems often use externally mounted pumps to move water through rigid pipes.


Use tubing to connect the water pump to your distribution system. Vinyl or air pump tubing is a popular option for a small or medium-sized cannabis automatic irrigation system because it is durable and easy to work with.

Drip irrigation system

 Install an automatic drip irrigation system to distribute water evenly to your plants. Most drip emitters are labeled in LPH (liters per hour), so make sure you properly size them for the growing containers you will use.

Programmable timer

 A programmable or digital timer is an essential part of your automatic irrigation system setting since it lets you control and adjust the watering schedules for your garden. A proper watering schedule gets more oxygen in the root zone without overdoing it. Keep in mind it is more beneficial for overall growth and yields to use less water more often (more “on” cycles) than using more water less often.

Other tools

Scissors, razor knives, or pipe cutters for irrigation lines. You can also use pliers, drills, hose clamps, pressure regulators, and fasteners to create mounting points.

Other Important Steps

Take samples of the water you’ll use to determine their hardness. Hardness levels reveal how much calcium and other minerals are in your tap water. You may need to use reverse osmosis if you have particularly hard water. 

A typical a self watering system for growing marijuana in an indoor grow tent
It might look daunting and expensive, but an osmosis filter can be a good investment to optimize the water quality for your cannabis plants

Filter the water you start with to reduce the potential for problems. This will reduce the amount of chlorine and chloramines in your water, which is detrimental to plant roots and soil biology. Be sure to learn more about preparing water for irrigating cannabis plants before setting up and running your system for the first time.

Automatic watering systems for indoor gardens

Systems for auto-watering cannabis work well in indoor environments with excellent climate control and relatively stable growing conditions. This stability will help ensure consistent, predictable results for the absorption of water and nutrients by marijuana plants with relatively little adjustment needed. 

The type of substrate you use will partly determine the frequency of your hydration schedule. Indoor cannabis grown in soilless substrates like coco and peat hold air better under wet or saturated conditions than indoor plants grown in soil. If you are growing in soil, read our tips for watering marijuana grown in soil for the best harvest possible, and be sure to download our famous Grow Bible by Robert Bergman to ensure maximum results for your indoor grow!

Expert Tip

Be sure to leave enough room for performing plant maintenance when setting up an indoor automatic drip irrigation system, including the reservoir and distribution lines. It’s easy for a grow room watering system to take up excess room, so plan it out visually before building your system. You should especially consider electrical needs, such as the power outlets where your water pump’s power cord and your digital timer’s power cord will connect.

When possible, set up the reservoir and delivery lines outside of the room and bring them into your room through the path of least resistance.

Before filling your reservoir, check out our guide on the best water for marijuana plants.

Grow tent irrigation systems

Grow tents are soaring in popularity, and a grow tent automatic watering system may be the first one that many new growers will experiment with. These portable grow rooms come in many sizes. They start at 2’ x 2’ but go larger, saving growers the time and effort it takes to build a room. 

Grow tent irrigation systems can be relatively small and simple to set up, and one grow tent watering system may be able to accommodate multiple tents at once. Again, they are small, so ensure you properly size your plants and pots for your tent, or you’ll run out of space. Read our article on growing cannabis in pots for more on choosing the best pots for your grow tent setup.  

A simple DIY grow tent watering system may consist of an elevated 5-gallon bucket above the canopy that hydrates plants via drip tubing using only gravity. Drip irrigation systems like a Blumat system are an example of this. This easy watering system for grow tent hydration works best in typical grow tents that are around 4 to 6 ft wide and deep.  A larger grow tent may benefit from an irrigation system with a pump.

A typical a self watering system for growing marijuana in an indoor grow tent
A typical a self watering system for growing marijuana in an indoor grow tent

Greenhouse irrigation systems

Greenhouse irrigation systems can be installed sub-grade (buried in the ground) and used to water the plants from below, using an autopot or capillary mat, or from above with a drip emitter staked into the top of the soil. Sub-irrigation can save valuable space. 

Greenhouses also provide consistent light, humidity, and temperature, so the watering system you select should work efficiently in these conditions. A greenhouse with built-in floor drainage or elevated growing tables is a great candidate for a cannabis drip system with coco or a coco auto watering system.

Automatic watering systems for growing outdoor cannabis

When it comes to outdoor self-watering systems for cannabis, the best auto-watering system for outdoors will accommodate your environment’s specific needs.

  • How big are your plants going to get?
  • What medium are you using?
  • In full sun?
  • How much wind or exposure?

These factors will help determine the type and size of your outdoor automatic irrigation system.

Outdoor automatic irrigation systems may require a bit more planning. You will need a good water source and adequate pipe or tubing to reach your plants’ location if you use a natural water source like a stream or creek. You will also want to camouflage your system components to avoid detection if growing guerilla. 

An automatic drip system is one of the most efficient ways to deliver water to outdoor cannabis plants. However, you may need to oversize your pump and pipe or tubing to deliver hydration effectively over long distances from a reservoir. You might also need to account for sun and wind exposure drying out your plants more often.

A simple automatic irrigation system setup for your outdoor cannabis plants
A simple automatic irrigation system setup for your outdoor cannabis plants

Automatic watering systems for soil-less hydroponic systems

Soil-less hydroponic systems were developed largely for indoor growing environments to help maximize the amount of biomass and yield from an indoor space. Example systems include ebb and flood tables, NFT, and aeroponics. These systems depend entirely on electrical pumps to circulate irrigation water and are used widely for growing many crops in commercial CEA operations (Controlled Environment Agriculture). The downside is the quick death plants can face if a pump fails or system power is lost.

Pros and cons of automatic watering systems

An auto-watering system for growing marijuana can save time and reduce labor. This is a convenience when growing a couple of plants and an absolute must for commercial operations. These systems will improve the efficiency of your growing efforts.

On the other hand, self-watering systems can make controlling the water flow to the plants difficult, especially with systems that work on set intervals. These systems can lead to overwatering, which can kill your plants. If you’re already on the wrong track (or worried you might be), read our article on underwatering and overwatering weed plants for help.

The best automatic cannabis plant watering systems are reliable, accurate, and specifically designed for cannabis plants. To avoid overwatering, it’s important to size and set up your watering system correctly and ensure it’s calibrated to the specific needs of your plants.

In general, you can use any irrigation system that meets these criteria, but some popular brands include Netafim, Grodan, and Blumat.

In summary

An automatic watering system for growing marijuana is essential for growers who want to keep their plants hydrated without the hassle of manual watering. Whether that is an auto watering system for a grow tent, an irrigation system used indoors, or a DIY drip system outdoors, many options are available to suit your needs. With proper installation and calibration, you can ensure healthy growth and a bountiful harvest.

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Jason Bird

Cannabis indoor cultivation expert

Jason Bird has been cultivating organically-grown cannabis in Portland, Oregon, since 1996 and graduated with an AAS degree i ... See profile