This thing was really simple to make, it only took a few hours really, and that includes letting some pieces dry.
The input for the loop is just 1/2'' PVC. It's a straight piece that sticks about halfway into the reactor. The output comes in and has a 90 d egree elbow that points down to the bottom of the reactor. I have it sitting about half an inch from the bottom. When the pump comes on, it mixes all of the kalk powder that has settled to the bottom of the reactor. The input / output for the RO / Kalkwasser liquid is standard airline size tubing. I drilled two small holes in the screw on lid, and pushed the fittings through. I had to silicone around one of them because it was a bit loose. I am going to use an aqua lifter pump to dose through this thing. I've tested it, and it works great. When the aqua lifter starts pushing fresh RO water into the reactor, the kalk mix comes right out of the other tube, it dosent take much pressure at all. I have the input and output airline tubing set to different lengths so that it wont just pull RO in one side, and out the other. The RO input tube reaches almost to the bottom of the reactor, while the kalk output is about one third down.
EDIT: I forgot to mention something about the pump. You need to use a powerhead that completely seals up, like a Maxi-Jet. The MJ pumps have an O-Ring seal that prevents any water from leaking outside of the unit. I tried one of the penguin 660's from the PX, but the damn things arent sealed at all. If you dont want to wait to get one in the mail, upper river sells MJ powerheads, although they are a little bit pricey.
