How to build a hydroponic system for growing marijuana (DIY guide with pics)

Although most people who cultivate outdoors grow in soil, it’s also possible to grow on hydro.

In this course I will show you how to build an easy hydro system for outside.

Also, I will keep up with a grow journal this summer and post an update every week so you can see what to do and what to look out for.

Why hydro

I’m going to build a simple system for two plants in 20 gallon tubs on clay pellets.

Water is pumped over the clay pellets multiple times a day from a reservoir. The pellets are only required to provide support to the plant with its roots. There are no nutrients in the pellets.

And this is actually the main advantage of growing on hydro. You can exactly determine how much nutrients your plants get, since there are no nutrients in the medium.

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The pellets also don’t absorb any. It is therefore impossible to overwater your plants, plus there’s a smaller chance of fungi and diseases. Hydro is a very clean method of cultivation.

The disadvantage is that it’s not organic, so your marijuana won’t get that nice ‘earthy’ flavor.

In addition, the wrong nutrient water has a bigger effect, since there’s no soil to form a buffer.

But if you have the space in your backyard, you should definitely try it some time, because the plants get huge and the yield is enormous.

Shopping list

You can get almost all required supplies from the garden center at the pond section, and I think the entire set won’t even cost as much as $50. Here’s a list with all the stuff I bought.

• 1 x old table
• 4 x 20 gallon tanks
• 1 x 65 gallon feed reservoir
• 1 x water pump
• 40 gallon of clay pellets
• 5 yard water hose, 0.35 inches
• 2 x 0.35 inches connecter and connector piece
• 3 x 0.35 inches t-splitter

Building the system

Marijuana plants come in many different types and sizes. There are currently thousands of crossings.

But they’re all based on a couple of types, which are crossed for their specific features. So let’s talk about some types and then about gender.

Marijuana can be divided into three types; Indica, Sativa and Ruderalis

Prepare the tubs

1. Drill about 30 little holes in one of the tubs. Not too big, because otherwise the pellets will fall through.

The point is to never have any water remains in this tub, because stagnant water can be harmful to your roots.

2. Now drill a bigger hole in the middle of the other tub. This is the drip tub that collects the excess water and transports it back to the reservoir.

Screw the connector piece firmly to the place a piece of hose will end up.

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3. The next step is to drill a hole in the table, the size of the connector piece. Place the tub exactly above the hole, so the connector piece sticks out through the hole.

4. Now put some stones or something similar in the tub and put the tub with the many holes on top of it. The stones will make sure the water will run well and the roots will never be too wet.

5. Fill the tub with clay pellets and do the same with the other two tubs.

Installing the water

1. Drill a hole for a water hose between the two tubs. The water hose that’s connected to the pump will come through this.

2. Make the water hose into a circle and connect a t-piece to it.

3. Drill about 15 holes in the hose on equal distance to each other. Do the same for the other tub. Make sure both hoses have the same amount of holes, to makes sure the pressure is balanced.

4. Connect the hoses to the t-piece of the water pump and we’re almost done already.

5. Place the water reservoir under the table and connect a piece of hose to the drip tubs and hang these into the water reservoir.

6. Install the water pump. Secure it with a clamp, since quite a bit of pressure will be on it. And that’s it!

Just make sure to test to make sure it works and it doesn’t leak. Doesn’t this look great?

It’s very easy to build and super cheap. And the big advantage is that you have full control over the water provision, the feed and the pH level.

You can cover the clay pellets with a lid or some plastic, so no rain water will reach the roots.

A lid on the water tank is also not a bad idea, just like a circulating pump. So you can make it as extensive as you want.

Water schedule

Only water the plants when it’s light. I usually start with three minutes an hour during the growing phase.

I slowly increase this to five minutes an hour. You could leave the pump running all day, because your plants can’t even get too much water with this method.

I usually keep the EC on 1.5. It could be higher, especially during the flowering phase, but the weather in the Netherlands is not very sunny, so I like to play it safe and keep the EC relatively low.

I lower the pH of the water once a week to 5.8.

During the fall I build a frame around it to tie plastic to, because the plants should be protected during rainy weather.

There’s a large chance of bud rot in outdoor plants, and I experienced this quite often. A wet fall is almost a guarantee for bud rot if you don’t protect your plants.

I will store this setup in my shed and take it out after the last frost and I will put two sativas in, because they will get huge.

I will also keep a grow journal this summer and show you what you have to look out for.

Let us know on the forum if you’re planning on growing outdoors and what your setup will be like.

Robert