You would also need some method of sensing the level of the water, possibly, if you were to use a water level float sensor in a pipe that is inserted in the dirt, this may work. Liquid Level Sensors - Float | Newark element14 Canada
Lastly, you will need the some sort of micro-controller that can communicate with the sensor and valve.
If you wanted to do this for many plants, then you would probably want to have individual valves and sensors.
This might not be the best way to do it, but it might work.
The best thing to do is to use drip system which will help you water the plants whether you're or aren't at home. way better then watering plants manually.
It should be pretty easy to use a micro controller with a electronically controlled valve and some type of moisture sensor. The micro controller can measure the moisture levels in the soil ever x-time interval and if the levels are below a certain amount the controller can turn on the water valve for an interval of time before turning itself back off. How the watering system would work could be up to you, but its possible to pipe it right into the houses water supply so you wouldn't need to ever refill the system and you would just have to check up on it to make sure nothing broke and your plants are healthy. I've seen some projects that use the arduino uno and an orbit 62035 hose water valve or adafruit sells a Plastic Water Solenoid Valve, which may be a better choice for an easier electronics setup but slightly more work in the piping works. This combined with something like the adafruit Soil Temperature/Moisture Sensor could be just what you are looking for. Although it take a decent amount of coding, and I am not positive if the orbit62035 can be ran straight from the arduino pin outs. Hope this helped!
It is a great idea to have it piped from the house, the only problem that would have to be watched out for is that if you have the pipe into the water, if the water pressure drops somehow (especially if you are on a well system), then you couls suck the water from the plant back into the system.
I would suggest that it drips onto the plant to prevent this; clean drinking water is always a good thing to have.
That is a great idea! I don't know what having a shower head would look like though, maybe if you have it poor into a funnel, then have the funnel piped into the plant, that way you can hide the funnel, and not have as bad of a risk for back washing.
