DVDdoug:
Irrigation valves sold at home improvement stores are usually the cheapest but I don't know what kind of fittings you'll find....Most solenoid valves are in the $100 range.
YIKES!
I had no clue these things were expensive.
I have found some $7.00 variants..
But not sure if they are swappable:
A $4.00 variant:
I am attempting to set-up something similar to what you see here in this image: (upper right corner)
How are they securing the fluid lines to the solenoids?
I will have roughly 3-8lbs of pressure in the 2-liter containers.. (havent worked out what works best yet)