This instructable will help you make a small, but scalable, drip irrigation system for your home that will:

save water
free you from having to water your plants every day
allow you to travel

You'll need :

a water tank you don't mind making a hole in
10mm (or 3/8") diameter water hose
drip chambers (the intravenous thing, no need for the needle)
access to a 3D printer

Step 1: The Water Tank

Since the idea is to be able not to water your plants every day, you'll need a water tank big enough to store enough water for all your plants for several days. Calculate the daily water requirements of your plants and estimate the size of the tank. If you were already watering your plants by hand, you already know how much water you were putting in.

The tank will have to be placed above the plants so that gravity can work in your favor. If you have enough space for an off-the-shelf tank (a plastic box, a bucket...), that's perfect. Otherwise, you'll have to make your own to measure. You don't have to make a water-tight, aquarium-like box, that's hard. Instead, build a box strong enough to hold the water and cover the inside with a nicely folded plastic sheet. If it's going to be outdoors, be sure the materials can withstand the weather.

You have to put a water tap on the bottom of one side of the tank. The tap must have a 3/8 inches (about 1cm) diameter hose connector (see the picture), which should appear on the outside of the tank. That's right, the tap will be mounted backwards. To open or close it, you'll have to open the tank and reach inside it.

If you built your own tank with plastic sheet covering the inside, mounting the tap backwards will make the connection water-tight so that the panels of the tank won't get wet. That means your tank may be made of wood.

Step 2: Print the Connector(s)

Please find the printable models here. Note that the files shared there are slightly different from what you can see in the pictures here. This is due to the fact that the files are several versions ahead of the pictures.

The connector should be printed with decent density (70%), shell thickness (.8mm) and top/bottom thickness (.9mm), so that it won't break when you plug things in and it can be made water-tight. See the pictures for the suggested cura configuration.

The connector has three 10mm hose plugs. This enables scalability. One connector can be linked to two others or closed with a hose loop. If it had only one hose plug, another water tap in the tank would be needed to provide four more drip chamber plugs. If it had only two hose plugs, it could not be closed with a piece of hose and would need some terminator cap or cork. This design, with three hose plugs, allows you to close everything off with cheap off-the-shelf hose, providing you have an odd number of connectors.

Freshly 3D printed objects are not water-tight. To make them water tight, objects printed with ABS must receive treatment with acetone (10s immersion in pure acetone). PLA-printed objects can be treated with heat so that the surface melts a little and seals off any fault. The temperature should be high and the treatment quick, so that the whole object won't melt down. You may use a solder blower over the surface. Don't forget the insides !

The connector has four 15mm sockets that will receive the drip chambers. For each, an adapter must be printed out of a flexible material like ninja flex, then fit into the sockets. The adapter was designed to receive a standard drip chamber with a 5mm diameter plug. Fitting the ninja flex adapter might be a bit hard. That's by design, make it loose and it won't be water-tight.

Step 3: Plug Everything In

Now just plug everything in. Again, plugging the drip chambers in may be a bit hard. If they were not, things would leak. Notice you can stick the tip of the drip chamber hose 1 or 2cm into the ground, so that even less moisture evaporates.

Then regulate the drip chambers' flow. Check the size of each drop on the drip chamber's package, as it may vary from 10 to 60 drops per mL, then regulate the flow so that your plants will have their daily water requirements met. There are some multiplications and divisions to do here.

Check the flow every several days, as the drip chambers' plastic hose tend to adapt its shape so that the flow is reduced over time.