DIY Automatic Watering System for Indoor Cannabis

DIY automatic watering system for grow tent. Hydro Halos. Cannabis

An indoor automatic watering system makes managing your cannabis grow easier and more efficient. Setting up an automatic watering system for your grow tent or grow room is not as difficult as you might think. It requires no special skills and all the information you need is right here. There are expensive kits available, but it is just as easy and far cheaper to purchase the things you need and put it together following the instructions below.

The automatic watering system that I describe is designed to allow you to water multiple times per day without supervision. Below you will find complete plans for a DIY Automatic Drip System for your grow tent. We also have plans for DIY Self-Draining Saucers and a DIY Auto-Pumping Drain Bucket to remove water from the tent. Together these three components create an effective, reliable, reasonably priced and easily set-up automatic watering system for indoor cannabis.

In this guide, I cover setting up the drip system. I include the components that you need along with assembly and installation instructions. I also cover the siphon effect problem that will limit the height that the water can be in your reservoir tank. This guide includes all the information you need to set-up and install your indoor automatic watering system for your grow room or grow tent.

Once you get the system in place, there are several keys to managing it properly. Be sure to read our "Guide to Automatic Watering for Indoor Cannabis”. We also have several articles and tutorials to help you feed and water your cannabis plants like a pro. Be sure to read “Growing Cannabis in Coco with High Frequency Fertigation” and “How to Water Cannabis Plants in Coco Coir” to get started.

DIY Automatic Watering System Overview

An Automatic Watering system begins with a reservoir, which should sit outside the tent or grow space. A pump sits in the reservoir and runs on a timer. The pump delivers water through one main waterline into the tent, where it is distributed to the plants using Hydro Halos or drip emitters.

My pots sit on plant elevators in “Self-Draining Saucers”, which empty to my “Automatic Pumping Drain Bucket”. The automatic pumping drain bucket resolves the problem with collecting run-off and prevents you from having to raise your pots within the tent. It automatically moves the run-off water from the tent to a separate bucket which sits outside the tent, next to the reservoir. This is a complete and reliable automatic watering system that any grower can assemble.

Automatic Drip System Components

Everything you need to put together the drip system for your indoor automatic watering system is listed below. These are the components that I purchased and use in my own system.

Reservoir Tank

When selecting a bucket, barrel, tank, or tub for your reservoir there are a few things to consider.

Size: You want a reservoir that will hold enough water to run your system for at least a day or two. In a 4x4 tent I can use up to 3 gallons per day.

Height: Tall reservoirs allow you to use fountain style aeration. However the siphon effect problem may limit how much water you can fill in a tall reservoir.

Color: The reservoir should protect the nutrient solution from light as much as possible. Avoid clear plastic or white containers that allow light to penetrate.

14-Gallon Plastic Drum
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This is the reservoir that I use. It is tall enough to use fountain style aeration and large enough to hold water for at least two days. I linked a similar drum for the UK, but could not find a decent option in Canada. If this model is a good deal in your marketplace then I recommend it. However, if it is expensive or unavailable then you should be able to find an alternative online or locally.

Irrigation Pump

The pump that you need for an indoor watering system is not very large. It needs to be powerful enough to raise the water into the tent and provide some pressure to ensure equal distribution. However that task can be handled by pretty small pumps. About 300 GPH should be the minimum for any auto-watering system. If you have a large grow you can estimate about 60 gph per plant to determine how large your pump should be.

We recommend running one pump for up to 8-10 plants. Running more than 10 plants on a single pump makes it extremely difficult to balance the distribution of water among the plants. If you are growing more than 10 plants, you should set up two systems with separate pumps.

400 Gallon Submersible Pump
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This is the pump that I use in my system and it works perfectly. I have had it for two years and have run 2 plants all the way up to 6 with this pump. This is a good option for almost all auto-watering systems for home grows.

Digital Timer

Digital Timer with one second intervals
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This is the best timer for automatic watering systems that I have found. It allows you to set watering intervals in one second increments, which allows fine-tuning an automatic watering system. This timer also has two outlets, so you can use one for the stirring/waterfall pump!


When you keep nutrient solution in a reservoir it is important to keep the water oxygenated. Water with a high level of Dissolved Oxygen helps to prevent bad bacteria and is great for the plants. For small tanks, up to about 30 gallons, air-pumps and air-stones provide adequate oxygenation. If you are run a larger reservoir or use organic nutrients then you should use a stirring pump to mix and oxygenate the solution. A stirring pump is a small fountain pump which should sit in the reservoir and run periodically to “stir” the nutrient solution. Be aware that both forms of Oxygenation will raise the temperature of the reservoir. The best way to avoid getting the reservoir warm is to use a stirring pump (instead of an air pump and air-stone) and run it only for 2-3 minutes before each event.

Air Pump
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I use the hydrofarm air pump and it is perfect for most reservoirs. It is easily adjustable and plenty powerful for a reservoir up to 30 gallons.

Air Stone and Tubing
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This is the perfect accessory kit to go with an air-pump. The kit comes with two air-stones, tubing and splitters that will allow you to use both stones with one pump and tube.

Stirring Pump
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A stirring pump is an alternative to air-pumps and air-stones. It is the preferred style of aeration if you have a large reservoir (over 30 gallons) or are using organic nutrients. Stirring pumps are small water pumps that sit in the reservoir and lift and stir the water. You can attach a small section of Poly tubing to the pump so that the water is lifted just above the surface of the water in the reservoir. Pumping the water just above the surface and allowing it to fall back like a fountain is one of the best ways to oxygenate water. If you use this “fountain style” aeration, then the pump should be run for a couple minutes every hour and prior to each fertigation event.

Aquarium Thermometer

It is best to keep the temperature of the water in the reservoir between 65-68f (18-20c). This temperature range helps to maintain dissolved oxygen and prevent infestation with anaerobic bacteria. Read more in our guide, “Guide to Automatic Watering for Indoor Cannabis”.

Digital Thermometer
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This is a simple thermometer to keep track of the temperature in the reservoir.

Main Water Line

This water line attaches to the pump in the reservoir and runs into the tent. I prefer “poly tubing” over “vinyl tubing” for the main water line. Poly tubing is a semi rigid tubing that bends gently and resists being crushed. When using the drip emitter system, you need to use this Poly tubing. With the Hydro Halo system, you could technically get away with using vinyl tubing for this task, however poly tubing is a much better option.

1/2 inch Black Poly Tubing
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50 feet is probably much more than you will need, but it is tough to find in shorter lengths.

Water Distribution Options

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I have used two different systems for distributing water to the plants. My first indoor system used feeder lines and drip emitters. I recently switched to using Hydro Halos. Both systems work well but have different advantages and disadvantages.

Hydro Halos offer superior water distribution. I can go weeks without hand-watering the plants because the distribution of water does not leave any dry spots within the media. The drawback to Hydro Halos is that they really can only be used in final containers – leaving you to hand-water all through the first several weeks.

Drip Emitters offer much more flexibility. You can put just one in a seedling pot and then add more as the pots and plants get bigger. The drawback is that you will end up with a lot of water lines running around and it can be difficult to set enough emitters in large pots to get good saturation.

Hydro Halo System

I think that the Bloom Brother’s Hydro Halos are the perfect option for a DIY drip system for indoor cannabis. They have greatly improved the distribution of water in my system from the dripper lines that I used to run. This can reduce or even eliminate the need for periodic hand-watering. They are also easy to use with Ball Valves to control the flow to individual plants.

6" Hydro Halos
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I recommend the 6” Hydro Halos for air-pots up to #5 and most fabric pots up to 3 gallon.

9" Hydro Halos
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If you use fabric pots that are 5 gallon or larger, you should opt for the 9” Hydro Halos instead.

½” Vinyl Tubing
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I prefer to use Poly Tubing for the main water line, but Vinyl tubing is required to actually connect the Halos to the system. I run the Poly tubing to a connector and both the poly and vinyl tubing can attach to the same connectors.

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This is a simple set of connectors that includes all of the pieces that you will need. Both the poly tubing and the vinyl tubing can attach to these connectors. Dip the tubing in hot water to make attaching it to the connectors easier.

Ball Valves
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You need to use a ball valve for each halo. The ball valves attach to the Vinyl tubing and allow you to control the flow of water to individual plants. These are required if you use halos.

Drip Emitter System

The drip emitter system offers more flexibility than halos. However, they do not distribute the water as effectively. If you set up a drip emitter system you should plan to hand-water at least once per week to flush out salts that can accumulate in the regions of the pot that don’t get well saturated by the drippers.

End Cap
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This system works by plugging the end of the main poly tube that comes into the tent. That forces water into the small feed lines that run to each plant.

Small feed lines: ¼” PE tubing
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This is the tubing that will attach to the main water line and bring water to the plants. You can use one, two, or more lines per plant.

Clamp and Pierce Connectors
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You may be wondering how the small feed lines attach to the main water line. There are several solutions, but clamp and pierce connectors are the easiest by far. You simply squeeze them onto the main water line and then slip the small feed lines over the fitting. They come in sets of 5 and you will need two connectors per plant.

In-Line Drippers: 1 GPH
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These in-line drippers help to distribute the water around the pot. You simply cut the small feed lines and then slip each end onto the inline drippers. I use two to four per pot. This set includes 25.

Terminal drippers: Adjustable Bubblers
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At the end of each small feed line you will need a terminal dripper. I use these stream bubblers. The water pressure created by the pump is not as high as normal water pressure. The bubblers are designed for outdoor use on full water pressure. On their labels, there are pictures where it looks like they spray water around – but in your indoor automatic watering system, they will just leak. Since they are adjustable, you will be able to control how fast they leak, but they will not really distribute the water. You need to distribute the water using at least 2 terminal drippers and 2-4 in-line drippers per plant!

Automatic Watering System: Set-Up

Anyone can set-up an indoor automatic watering system. It requires no special skills or knowledge. The only tools you will need are scissors or snips to cut the water lines and a drill with a with a 3/4” bit to make the hole in reservoir tank for the water line to pass through.

First, prepare your reservoir. You need to drill a hole near the top of the reservoir tank for the main water line to pass through. A 3/4” drill bit creates the perfect size hole for the ½” poly tubing. The pump sits in the bottom of the reservoir along with the airstone and thermometer probe. I cut a hole in the lid to pass the power cord, air-pump line, and thermometer probe.

The poly tubing attaches to the pump and exits the reservoir through the hole that you drilled near the top edge. This main water line should reach its highest point as it exits the reservoir and then it should descend to the plants (see Side View Schematic below). This ensures that the line drains back into the reservoir after each event.

The water line should enter at about the height of the top of the pots and stay at that height. I cut a hole in the tent where I needed the poly tubing to enter the tent. Don’t think of this as damaging your tent, you are customizing it. With the Hydro Halo system you will attach a connector to the poly tubing to connect the halos. With the drip emitter system, you should run the poly tubing across the tent from one side to the other.

Option 1: Hydro Halo Assembly

I like to assemble the "hydro halo manifold” and then bring it into the tent to connect it to the main water line (poly tube). Both the poly tubing and the vinyl tubing can attach to the same connectors, but it can be a little tricky. Poly tubing is easier to work with, however, the ball valves and Hydro Halos only fit on the vinyl tubing.

You can set up anywhere from one to 10 hydro halos per manifold/water line/pump. The more halos that you add to the system, the harder it will be to adjust. Therefore, we recommend running additional systems if you have more than 10 plants.

Both poly and vinyl tubing can be easily cut with decent scissors or snips. Get a cup of hot water to dip the tubing and use a little force to slide the tubing onto the connectors. Refer to the picture and diagram for order of assembly.

Note: The hydro halos and ball valves will only attach properly to vinyl tubing. However, I use poly tubing for the short sections between the connectors because poly tubing is far easier to get onto the connectors.

Tip: Getting the vinyl tubing onto the connectors can be tough. Dip the tip of the vinyl tube into almost boiling water. It becomes very pliable, but also very hot so be careful! It needs to get over the collar of the connector, but that is all.

Option 2: Drip Emitter Assembly

If you are setting up the Drip emitter system then you should run the main water line (poly tube) straight across the grow tent or grow space. This brings it close enough to all of the plants and gives you plenty of room to attach the feeder lines. The clamp and pierce connectors do exactly what they say they will do: clamp and pierce. Just position them along the main water line and push them onto the line. The barb should easily pierce the poly tubing and self-seal. The small feed line can be cut with scissors. You simply attach a section of line, cut it to length, attach an in-line dripper, and then another section of line. The terminal drippers are inserted last. Everything just goes together with a little force. If you are struggling, you can dip lines in hot water and it will be easier.

The bubblers should be placed such that the two terminal bubblers are across from each other at (12 and 6 positions of a clock) and the inline drippers are filling in the gaps (3 and 9 positions). See the Overhead View Schematic and the pictures.

Adjusting the Flow to Hydro Halos and Drip Emitters:

After the initial installation, you need to run the system to adjust the flow to each plant. For the first event, turn the ball valves or drip emitters almost shut and turn on the pump. Open each ball valve or emitter until water is coming out slowly but evenly. After all of the valves have been adjusted once, go back through and adjust them again using the visible flow as your guide. During this initial adjustment, your plants will likely receive plenty of water.

Wait for the next fertigation event and run the system again. This time, run the system until you are sure run-off will emerge. Watch how long it takes run-off to appear from each plant and adjust the valves accordingly. Your goal is to get all of the plants to produce run-off at the same time. Once you dial that aspect in, you simply have to adjust the duration of each event to deliver just enough water to produce run-off. It may take 4-5 events of watching and adjusting before the system is fully tuned to your grow.

Timing the Watering Events

The duration of each event should be long enough to produce run-off from each plant. I have used events as short as 35 seconds with hydro halos and as long as 2 minutes with drip emitters.

If you are growing in coco, see our article, “How to Water Cannabis Plants in Coco Coir” to determine how many fertigation events you should schedule and when you should schedule them.

Caution: The Siphon Effect!

The water level in the reservoir must be lower than the height of the drippers. Otherwise a siphon will be created, and water will flow out of the reservoir until the water level is at the same level as the drippers. In my set-up, my plants are high enough that I can keep 8.5 gallons in the tank without siphoning.

The Drip System is just one part of an Automatic Watering System

This system must work together with a drainage system. Each fertigation event should produce run-off and you won’t always be there to remove it. See our instructions for "DIY Self Draining Saucers" and a "DIY Auto-Pumping Drain Bucket" for an easy drainage solution. Be sure to read our "Guide to Automatic Watering for Indoor Cannabis".

Self-Draining Saucers

To get the water away from the plants

An Auto-Pumping Drain Bucket

To remove the water from the tent

Author: Dr Coco

I am a university professor and have taught courses in horticulture. I am coco for cannabis and I hope you are coco for cannabis too :) Grower Love!

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You are responsible for knowing and following the local laws that pertain to cannabis cultivation, possession, and use. Decisions to grow cannabis should be made in consultation with a lawyer or qualified legal advisor. Decisions to use cannabis should be made in consultation with your doctor or medical professional.