fishforme
What you're decribing I've seen in many industrial waste treatment applications. Most of those people use multiple pumps ( cause they got the money ).
In your case though, trying to save some bucks and use 1 pump, you would need a manifold dispensing system, set up with a bank of several solenoid valves as you've described, each valve resposible for opening/closing the line to one of the additive bottles, allowing the 1 pump to dispense only the one additive at a time, on some predetermined rotating time basis.
I'm sure given enough time and money you could put together such a system, providing you can locate all the parts and not totally wipe out your wallet while doing so.
Couple things to consider comes to my mind.
You'd want to stick with solenoid valves that have only plastic wetted parts, pvc, teflon, or any other chemically inert thermoplastic. Solenoid valves consist of the valve body, orifice, inlet/outlet ports, sleeve that contains the plunger, plunger and seat, coil, and coil housing. As long as the "wetted" parts are a form of plastic - you'd be good to go.
I'd recommend staying away from any valve that has metal wetted components. You would certainly need a "Direct Acting" type of valve, normally closed, energize to open. The plunger/coil arrangement will operate whether there's line pressure in the valve or not. Do not get a solenoid valve that relys on differential pressure, or the difference of line pressure to assist in it's opening. You will NOT have the necessary DP across the valve for it to operate ... and it will stay closed when energized. Also .. if one of the valves fails open, you would have more than one additive being dispensed ... not good.
Although most of the additives we add to reef tanks are not overly agressive, you'd risk some level of contamination/corrosion with metal parts. Kalkwasser by all means is agressive and would eventually destroy the metal valve, not to mention the ill affect this could cause your reef life.
When the timer circuit closed the valve to say Trace Element "A" , and the next valve in sequence opened for Trace Element "B" , you could easily still have some of the "A" liquid in either the pump, or pump discharge tubing, or both. Unless you used a peristaltic type pump. But you'd still run the risk of having leftover liquid in the tubing of this pump anyways.
This may cause some small amount of mixing of the "A" liquid and the "B" liquid where they meet. Not sure if that is a huge problem, but some additives are intended to be dosed individually. An example would be if you are using two part balanced ionic supplements such as C-Balance or Kent's Tech-CB. Not recommended for these to be dosed at the same time, nor mixed for that matter. So you'd want to address that for sure.
That's about all I can think of right now.
I wish you luck .... and let us know how you make out
Brian
