This Bottle-dripper is designed with a water-tight screw-lid for EU plastic bottles (PCO 1881) and is one of the only bottle drippers on this platform that is not leaking from the bottle cap. Also, it can be adjusted to drip very slowly, because what good is an irrigation bottle that drips out in an hour?

With the adjustment screw the drip speed can be reduced to one drop per several seconds so that a large bottle can hold up to two days. 

If the flow is still too high you can reduce it by placing a bit of cloth in the screw-hole and tightening the screw with it. 

The spike is designed to hold even 1.5L bottles but you may want to bind them to a stake to avoid them from tipping over.

Don't forget to make a tiny hole in the top (the bottom of the bottle) to let air in, otherwise either the resulting vacuum will crush the bottle or the flow will just stop.

If you want to copy and modify the model you can check out the public OnShape CAD model.

If you are interested in irrigation solutions you may also want to check out my printable tube-based low-pressure irrigation system.