Automatic Watering for your Cannabis Grow

In this article we’re going to talk about how to set up automatic watering for your cannabis grow, something that can genuinely be a lifesaver for growers that have spent years hand-watering their plants.

Technically, 100% automatic watering is something that still can’t be done, but there are systems in which, if you pick the right substrate, you can water a large amount of plants by simple keeping a tank full of water. This can be helpful if you’re growing a rather large amount of plants so that you don’t have to spend hours watering them all.

If you decide to use this method, keep in mind that your plants won’t grow the same than if you were to hand water them and mind them one by one – if you have lots and lots of plants, then doing this is probably not in your best interest. You can also do this if you don’t have time to water your plants and you only have a few in your grow tent, but keep in mind that the yield will be a bit lower.

If growing in soil you should only begin watering automatically when you’re sure that your plants are drinking a reasonable amount of water per day. In my opinion, I think automatic watering in soil should be used no earlier than when flowering begins, and in a 7L pot your plants should be drinking about half a liter of water a day.

You need to program the watering so that when it waters, it only gives your plants the amount of water they need for one day – you can’t water a 10cm plant with two whole liters as you’d end up soaking the soil, the roots will rot and you’ll probably end up with a dead or hardly productive plant.

If you want this to be more efficient, then you should grow in coco coir which dries up faster than soil, or in coco coir or rockwool slabs. These kinds of substrates drain the leftover water efficiently, so even if you manage to over-water your plants they should dry up soon enough and your roots won’t rot. This means that you’ll be able to water much more efficiently in this medium. Once your plants are big they can dry out our pots or slabs two or three times a day, needing to be watered more than once but this can easily be controlled with a digital timer.

If you’re growing in soil it can be hard to get the timing right, and if you mess it up twice in a row your plants will suffer quite a lot, which is why we recommend using a different kind of substrate with better water drainage if you want to use this automatic system.

Automatic watering is as easy as having at least a 2L tank per plant. You can even prepare enough water for a week, so the most you need to use is 1.5L per plant for 7 days – this is perfect as a week is about how long mineral nutrients can last in water without going bad – if you use organic nutrients you might end up blocking the pipes and you’ll also need to mix them every day as they won’t last more than 24h in the water without going bad.

You need to place a submergible pump into your tank which is capable of maintaining pressure in the pipes, so that the same amount of water comes out of each micro-pipe so that, logically, the plants all receive the same amount of water. You’ll need to install a pipe system that then connects to micro-pipes used for drip irrigation – make holes in the main pipe system for each of your micro-pipes which will then be used to water your plants. You can get pipes that can deal with 16 of these micro-pipes, or drippers such as the Octopussy, which has 6 micro-tubes etc.

Now you need a growing table so that the water can drain out under the flowerpots and flow into a tank which you can then empty – never reuse water from these kinds of systems, and always ensure that your timing is right so that you don’t waste precious water and nutrients, as you’ll basically be throwing money down the drain.

You should have your system set up by now, but you still need to know how much water is being pumped per minute by the pump. Place a glass at the end of one of the drippers and turn the pump on for one minute with the timer to see how much water your plants will be getting per minute. Once you know that, you’ll know how long you’ll need to have it on for when watering. Generally, half a liter per minute is what most pumps give – if you get more than that then your pump is much too big – you need about 1000L/H per square meter of grow with 16 plants in each square meter for the micro-pipes to work correctly.

The last thing you need to do is get an air pump with an air stone, which will ensure that the nutrient mixture and the water is in constant movement and oxygenized – your fertilizers won’t end up accumulating on the bottom and will always be available for your plants once the pump turns on.

Each time you need to fill the tank up again pay attention to how your plants react; if they’re soaked, if they’re too dry, anything that could indicate you need to change your method or water them more/less. They should grow massively and if you’re using slabs they can grow so big that you’ll have to water them up to 3 times a day.

Automatic Watering for your Cannabis Grow – Material needed

Automatic Watering for your Cannabis GrowFlood table:
These are trays that have grooves in them so that you can direct any leftover water to a specific point, where you can then channel it through a pipe to wherever you’d like or simply leave a tank underneath the hole on the tray itself so that the water can fall down into it. These trays are easy to clean once the grow is done and they’re very efficient when it comes to getting rid of water so that there’s never any leftover water sitting at the bottom of your pots and soaking into the soil. They’re also useful in the fact that leftover water from one plant has the opportunity to be absorbed by another plant, which can help avoid all sorts of salt excess in the substrate and whatnot. There are various sizes available to fit your exact needs.

Water tank:
There are all sorts of water tanks out there that you can use, although we recommend using one that has a lid if you’re growing with chemical or mineral nutrients, as they’ll last the full week and the water will be better conserved if it has a lid – there’s also less possibility of getting fungi infestations and algae that tend to occur when light hits the water- You can also use one of the square tanks without a lid and place it right under the table or inside a grow tent, which can save a lot of space. You need to pick the type of tank but you also need to pick the capacity – the most you’ll use per day is about 2L per plant once they’re fully grown and drinking the most they’re going to drink, so calculate that into about a week of growing and get the right sized tank.

Automatic Watering for your Cannabis GrowWater pump:
You’ll need a submergible water pump that can give out about 1000L/H per square meter of grow, which is about 16 plants. With this pump you can rest assured that you won’t be pumping too much water per minute, so there’s no need to worry about accidentally over-watering your plants. The minimum amount of time you can program is one minute, and make sure that in that minute no more than half a liter is being pumped out. You need to clean your water pump for every new grow to make sure that it keeps working perfectly – if you wait too long to clean it, it might get all blocked up and break due to the salts used in the water. Make sure to buy a quality pump, and not the first one that you see, as your entire grow will depend on this pump working properly.

Automatic Watering for your Cannabis GrowWatering pipe:
Automatic Watering for your Cannabis GrowThis tube is used placed in a straight line between two rows of flowerpots or slabs, and the micro-pipes are used alongside the sides of the main pipe – the main pipe is in the middle and then the plants are to the right and left of the pipe, kind of like a corridor. You’ll need one line of pipe per two rows of plants and then you need to place the micro-pipes – there are various models, some of them just need one hole in the main pipe and have 6 different drip pipe endings, some have 12, and some require one hole in the main pipe per drip pipe. You’ll need to pay close attention to the pipes in case they accidentally end up blocked – if you use Ata Clean in your grow about once a week then you can forget about worrying about blockages in the micro-pipes.

Automatic Watering for your Cannabis GrowRockwool or coco coir slabs:
Slabs are growing systems that are similar to hydroponics, where the growing medium is wet and then dried often, so it needs continuous watering, and these substrates hardly retain nutrients so you need to add nutrients in almost every watering. You’ll need to plce five slabs on your flood table, cut an X shape in them and place clones in the hole, from 3 to 5 should fit. Place a drip pipe at each plant and all you need to do is pay attention to when it dries up to know how often you’re going to need to water per day.

Automatic Watering for your Cannabis GrowAir pump:
Air pumps are used to give the water in your tanks more oxygen as well as keeping the nutrients in constant movement, which is something that your plants will greatly enjoy. You’ll need to place an air stone so the oxygen particles are smaller and easier to mix up with the water.

With all of these objects you can easily set up automatic watering for your plants, a small comfort especially if you have a large amount of plants. Don’t forget to keep everything nice and clean so the micro-pipes don’t end up blocked, no algae grows in the tank and no rot begins appearing in the water. Happy growing!

Author: Javier Chinesta
Translation: Ciara Murphy