Autonomous Plant Watering

Here in our house we keep our plants on the threshold of death. They are in constant limbo as we remember to water them every few months. It is really quite disgraceful.

A pathetic house plant
Our sad sad plant.

One day I looked at our plants and thought we needed to do something. Go and water them? The plant doesn’t just need water. It is suffering from the systemic problem of us never remembering to water it. No. Watering the plant would be too easy, we need a technological solution that will hydrate the plant and not require us to change our comfortable habit of neglect.

I googled “automated house plant watering” and the first link that comes up is an instructable. It promised to be a cheap and easy project. So I went ahead and got all the materials: an aquarium air pump, some tubing and valves. I then followed the instructions and assembled the parts as they describe. The result was underwhelming. I got some gurgling at the plant end of the tube, not a steady or measurable flow. I really don’t understand the physics that makes that system work, but it has a lot to do with water pressure: the deeper your reservoir the more efficient the water gets pumped. As the water gets consumed, the pump gives less output. So to get an optimal plant-watering we would need to make sure the tank is always full. Whats the point of automating it if you have to fill the tank after every watering?? This won’t do. I plan to put this on a timer. I need to know that if I have it on for 1 minute I will always pump a comparable amount of water to the plant.

So I got to thinking, how can an air pump pump water? Specifically, how can it pump water with a constant pressure? I came up with this schematic:

Brilliant schematic
Air is pumped into a sealed jar with an outlet tube that relieves the jar’s pressure by pushing water out through another tube!

I grabbed a mason jar and drilled two 3/16″ holes in the lid. This allowed me to insert the two air tube which are slightly thicker (5mm). They fit snuggly and formed a seal.

Jar lid with two tubes running through

Next I attached one of the tubes to the pump, and placed the second one’s end in a glass. Turned on the pump and! Yes! It works! Science! I was getting a steady flow of water. The jar was emptied in a constant rate. This setup will do. I’m so pleased with this!

I splurged and got a slightly more expensive pump with 4 outputs so I can water 4  plants individually.

Aquarium air pump with 4 outlets

This setup has a few advantages over other pump setups:

  • It is cheap. So far the bill of parts is around $12.50.
  • It offers predictable water throughput.
  • You can connect any sealable container. Don’t want to refill the water after 32oz of watering? Get a gallon jug.
  • If the reservoir runs dry the motor won’t catch fire. That apparently is a thing water pumps.
  • Since the water is only going through a simple tube and not an expensive motor, you can pump a nutrient solution. If you want to pamper your plants, we don’t.

I made a stupid pump. Why is that cool? Because with a WiFi plug it becomes smart! It is now a Connected Device™. I plugged it into a Bayit WiFi socket, and set it to turn on for 20 seconds each Monday afternoon. That will feed our plants about a 1/2 a cup a week. If we like the results we may extend it to a full cup!

Bayit WiFi Socket
The Internet is in control!

A Word on WiFi Sockets

They suck. They take the simplest operation of closing a circuit and abstract it in a shitty smartphone app that only works half the time. Well, at least that has been my impression with this Bayit gadget. For my next project I am going to use a Kankun smart plug. Apparently it runs OpenWRT and is very hackable.

Bill of Materials

Air Pump $6.99
Air tube $3.42
Mason jar $2.09
Wifi plug $24.99
Autonomous Plant Watering

21 thoughts on “Autonomous Plant Watering

    1. Eitan says:

      Yeah, I got the more expensive one with multiple outlets. The cheapest listed one was ~$7, it would probably work fine for a single plant.

  1. JJ says:

    Nice trick! I recently got a water pump.. and ordered an old school mechanical wall socket timer for it. No way to set 20second intervals on that though, so I like the wifi socket idea better! Where in the potted plant are you feeding the water? The surface? Down the side down deep?

    1. Eitan says:

      Not sure I understand the question.. are you asking if the pump can move water higher than the tank’s level? a bit. If you get the multiple-outlet air pump you can increase the pressure with a few inputs into the sealed tank. I have one air outlet per tank and it sits right next to the pot, so not much elevation change.

  2. yoad says:

    Do you think it’s possible to put 1 air line into 1 water container and have 4 outgoing tubes from it?

    1. Eitan says:

      You can.. the problem is the distribution will not be even. Depending on the height of each tube’s outlet you will get varying pressure from each. If you figure out a solution for this, I would love to know!

      1. Simple have 1 tube from mason jar get a splitter into 4
        u will need to use a larger hose and 4 smaller ones. I did somthing similar on my co2 setup i had 1 tank yet 50 outlets all came out at same presure tho this is gas not water but should work the same.

  3. […] [Eitan] is one of those guys whose plants keep tottering between life and death. Can’t blame the plants, because he just keeps forgetting when to water them. But keeping them hydrated requires him to get off his butt and actually water them. Surely, there had to be an easier solution which needed him to do nothing and yet prevent his plants from dying. Being lazy has its benefits, so he built his own super simple Autonomous Plant Watering Thingamajig. […]

  4. […] [Eitan] is one of those guys whose plants keep tottering between life and death. Can’t blame the plants, because he just keeps forgetting when to water them. But keeping them hydrated requires him to get off his butt and actually water them. Surely, there had to be an easier solution which needed him to do nothing and yet prevent his plants from dying. Being lazy has its benefits, so he built his own super simple Autonomous Plant Watering Thingamajig. […]

  5. Alwyn says:

    Here’s a 5V (USB) water pump for less than $5V:

    http://www.aliexpress.com/item/LS4G-DC-5-5-12V-3W-USB-Micro-Submersible-Water-Pump-for-Aquarium-Fountain-Pond/1330840105.html?spm=2114.01010208.3.1.idtj0U&ws_ab_test=searchweb201556_7,searchweb201602_4_10037_10017_507_10032_401,searchweb201603_9&btsid=4234327f-b216-499f-be6e-db7f618471eb

    I would put it in the bottom of a tank of a toilet, so that it will automatically refill when it needs more water. That would be zero maintenance and safe from flooding or fire.

  6. merc says:

    While this is a great idea, it is in no way a new one. This method has been used for non-precise dosing or auto-top off systems in small aquariums for many years.

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