First and foremost Dan and I found a pump to use for the various fluids involved in our system. A wonderful online homebrew supply store called MoreBeer.com sells a 3.5 GPM pump made with polysulphone (a food grade plastic) for $130. It's a bit more expensive than I was anticipating, but after a bit of checking, this turned out to be a decent deal. Most stainless steel pumps of similar capacity are usually twice as expensive. Unfortunately, I haven't had much luck yet finding a good deal on electropneumatic valves that are cheap and made of some food grade meterial. There was one company I briefly checked out called RyanHerco that specializes in fluid flow equipment, but I could find anything there under $100. Dan and I we're thinking that initially we might just stick with manual ball valved, and then add electro-mechanical valves in the future.
In addition to the pumps and valves we need a piece of hardware connected to linux box (preferably through a serial port) that can turn on and off the pumps and valves as well as take in analog signals from things like temperature sensors. Now, since I'm not an EE I do not have the ability to build such a device from scratch. That's where QKits comes to the rescue. They have a ton of these really cool electronics kits that you can either solder together yourself or buy pre assembled. You could say that they're the IKEA of hobby electronics. They have several serial port analog i/o kits that I'm considering. One in particular has 8 analog outs (connected to relays) and 4 analog inputs. They also have a temperature kit that allows up to four temperature probes to be read from a serial port. Anyway, when I get the chance I'll start posting some technical drawings. On Friday expect a description and some diagrams of the water system.