I would like to use a drip irrigation system for my houseplant, for fun and to hopefully go from watering it daily to maybe checking up on it weekly. I don't want to deal with connecting it to my actual plumbing, so I want to use a large water tank as the water supply. In my mind, I should be able to set it up so that so long as there some amount of water left in the tank, it will deliver water at a constant, very low rate to my plant. Whenever I see the water level get too low I can refill the tank (which should be once in a couple days or so). This implies that I must somehow keep pressure constant, I think I can set up an intermediate water reservoir with constant water level using a floater valve, or I can just connect a very low pressure regulator (I've found a cheap one that is 5 PSI).
After shopping around for emitters, regulators and valves, however, it seems like all the readily available parts are designed for scales much higher than what I want:
- My plants seem happy with about a liter per day (possibly less) and the smallest emitter I've seen is 0.5 gallons per hour.
- Common PSI ratings for the emitters are 50-60 or so. Even the mini emitters seem designed for close to 15 PSI. In order for me to provide 15 PSI through gravity, the water column would have to be many meters high, which seems impractical.
- Based on some simple calculations, I find that if I just punched a hole in my tank, even with a water depth of just 10 cm, I would need a ~50 micron hole to drip water at 1 l/day. This is obviously beyond my limit to construct precisely.
It seems like I need either a very low pressure regulator (<1 PSI), a very low rate emitter which operates at low pressure (order of 0.1 PSI) and provides a very small flow rate (order of 0.01 GPD), or an adjustable emitter that can be accurately set to tiny fractions of its maximum. I suppose another option is to find a valve that can be precisely opened so as to have a defined, micron-scale aperture (which I suppose is what a dripper is, in a way).
Closest thing I was able to find was this: https://www.homedepot.com/p/Elgo-Planters-Drip-Kit-12-Dripper-Set-ELCDK12/301617796 The description is unclear about the minimum pressure and how tunable it is, but it does claim a flow rate of 0.35 GPH, which is somewhat close to what I need. But I don't understand how much less than 0.35 GPH it can do.
Just to be clear: my question is of a purely practical nature. I know people set up drip irrigation in larger gardens, greenhouses and fields all the time and the components seem to be readily available. Surely if it so easy to do with larger flow rates, setting up a miniature version with low flow rate must be no problem, but I can't figure out how to get the flow rate down to the level I need.
I know I can use a timer or electrovalve, but I'd like to keep this project purely hydraulic if possible, out of personal preference.
I haven't specified a plant because I feel like if such a system is set up properly, it should be very easy to tune the exact amount delivered. Then I can adjust it depending on my needs. In fact the ability to precisely control amount of water is part of my motivation.