Self Watering Pot Plate

Hi.

Sometimes we can travel or be absent at home for a long time. If we have an indoor plant we have to find someone to water our plants until we far away. Market solutions give us such possibility, but that requires changing the whole pot, because of the built-in irrigation system.

This project is a remix of the idea for the self-watering solutions, many examples could be found on the web, here are some of them:

- https://www.instructables.com/id/Self-Watering-Pl...
- https://www.instructables.com/id/Self-Watering-Se...
- https://www.instructables.com/id/Self-regulating-...

In this instructable, I'll share with you an idea, how to create a self-watering pot plate that could be used with any existing pot plants or trays. It doesn't require changing the soil or something else. All that needs to be done is to connect any empty bottle with some tubes to the plate, put the potted plant into the pot plate and that's it! Please check the main attached video. It requires no electronics, relays valves, or other mechanical parts.

Supplies

• 25 cm silicone tube Ø 8mm
• 35 cm silicone tube Ø 3mm
• empty PET bottle, e.g. from water or milk
• 3D printer
• Fusion 360 (optional)

Step 1: Some Theory

Before we start we have to understand, why 2 tubes being used and how to make it work.

Because of the surface tension of the water, it will not flow through one thin tube, because of air bubbles, that will block flow inside the tube with ≈10mm in diameter. That is why, this project using 2 silicone tubes, one inside the other, to separate flows and let water flows without obstacles. This step contains a schema of the flows.

The bottom ( pot's plat) end of the tube should be lower for ≈3 mm than the slotted hole in the plastic pipe. In this situation, water will be flowing lower than air will be sucked back to the bottle.

The top (bottle) end of the tube should be higher than the outer one, to reduce the chance of sucking air inside the tube with water.

The main rule here is that fitting from the bottle end has to be above the fitting from the pot ≈1-2cm

Step 2: Models

If you have a pot with a bottom diameter ≤ 85 mm them could be grabbed and 3D printed. Also, you can design own models, a comprehensive step by step guide could be found in the next steps.

Step 3: Modelling the Pot Plate

The pot model, that is attached to this instructable is suitable for the average pot in my local area. If you have different pot sizes or shapes, and not very experienced in Fusion360, you can follow the video guide and images to create your own in an easy way. It'll take ≈15 minutes with no rush.

Note: Experiencing some problems with attaching the video to the instructable, so temporarily putting the link here, until the issue will be solved by the site admins. https://www.youtube.com/watch?v=ex9NwSd_v4Y

Step 4: Modelling Fitting for the Bottle

You can also create an own model of fitting in the same way as the pot was created in the previous step. Size examples could be found on the attached images to this step.

Step 5: Assembling the Bottle Cap

Drill/cut the hole in the bottle cap Ø 11mm

Apply some super glue and Insert the inner fitting into the cap. Once fitting inserted apply super glue and cover with the second part of the pipe. See photos for reference.

Step 6: Assembling the Pipeline

In this step, we have to assembly out a pipeline that connects the bottle with a pot plate.

1. First of all, we have to connect a bottle cap with a plate by using the outer tube. Simply pull the tube on both fittings.
2. Thread through the outer tube our tiny one and make sure that it ends for 3-4 mm lower than the top edge of the slot hole. Please check the second photo, attached to this step.
3. Leave an extra 2-3 cm tube length on the second end of the tube and cut it. Check the last photo for more details.

Step 7: Finishing

All that we need to do here is to place the bottle in the holder, screw the cap with tubes and place the plant.

That's it!

Thank you for reading and happy planting

Comments

[WORMSS]

Love that this technique can be used with any size water bottles..
Do you think a quad connection could be created and used on the bottle side to feed 4 plants at once? (the plant tray side side would be identical)
Or do you think the multiple air tubes would interfere with each other and send things out of balance?

[IgorM92]

Nice to hear that you like that idea. Yes, Any bottle size could be used, from very small to quite large.
Regarding the quad connector or similar things. They will not be working correctly and will be hard (impossible) to control the water level in this manner. So, 1 bottle - 1 pot.
As an option, you can print the standalone fitting for the pot and glue is to the bottom of the large reservoir, then place pots into it.

[jeanniel1]

So a large tray holding all the plants and one reservoir to fill up from one bottle (large), right? That'd be the easiest way to do it. Put the reservoir in the middle! I'd make the bottom tray to conform as closely to the plant pots as possible so water won't be wasted through evaporation at the sides.

[IgorM92]

Yes! That's correct.

[GaborS47]

They would interfere. As long as air can get into the bottle from any of the outer tubes, water can flow out on all of the inner ones.

Moreover, if there is a large enough height difference between the pots (like one on a table, one on the ground), then as the water is gravitating towards the lower tray, it can even suck back the water from the upper one, and as soon as you have a tube end in open air, all the water will flow down as there is no pressure difference to to stop it.

A third (although rather theoretical) limit is that the height difference between the bottle and the tray should be less than 10 meters, because it' the atmospheric pressure of the surrounding air (pressing the water surface in the tray) that is counteracting the gravitational pressure of the water in the bottle, and 1 atm = 10 m H2O (roughly). If the altitude difference would be higher, then near-vacuum would form at the top of the bottle, just like it does above the mercury in the barometers.

And the last (and rather practical) thing to take care of is that the bottle should be strong enough not to crumble, because if it can, it'll lose volume instead of losing pressure, and the water would just flow out again. (Think about how the intravenous infusion works.)

By the way, if the outer tube is thick enough so air bubbles don't get stuck in it (by the surface tension and the friction), then it would work even without the inner tube. That's how the bird water feeders work, where the "outer tube" is the water canister itself.

As long as air cannot get it, water cannot get out, and as soon as the end of the tube gets under water, the air no longer can get in, so the water flow stops. That's the whole principle.

The really nice trick of this article is separating the water- and air-flow by the inner and outer tubes, because otherwise we'd need thumb-thick garden water hoses running around, and that would be just too ugly :).

[IgorM92]

Thank you for the very detailed comment. Not sure that I can add something more :)

[Eating Pears]

Great idea! I’ll have to make one once my printer is up and going again.

[IgorM92]

Thank you for the comment. Nice to hear that!

[sharpstick]

I would just use a tube that's larger than 10mm so it doesn't airlock.

[IgorM92]

Thanks for the comment. The idea of that remix was to avoid large tubes and things. Your idea is also good, but for that purpose hose has to be more than 15 mm with inner diameter. Not sure that it'll be looking great.

[tercero]

Great idea. I'm about to bring my cannabis plants in (second round) for the season and put them in a grow tent. Making sure they stay hydrated is important (I'm a first time grower so it's sill a learning curve...and I'm in Canada. Perfectly legal to grow cannabis for home consumption here btw).
I'll adapt your idea for my seedlings. Thanks.

[IgorM92]

Hi. Thank you for the feedback. Nice to see when ideas are implemented and used by others.