This is how mine works;
- it's basically a sealed tube, with a pump plumbed in. Therer are two valves, one at the TOP of the "reactor" and one midway up
- I add kalk powder (random amount) to the reactor and it settles at the bottom of the tube
- Every 6 hours or so, the pump turns on and mixes up the kalk powder into the water. The pump is plumbed to take water half way up the tube and pumps it into the bottom of the tube, thus making sure the powder is nicely mixed.
- I have a medical perestaltic pump (basically a slow pump that I can control the flow rate of, say 100 ml/hour) which pumps RO water from a container into the valve at the middle of the tube. The way perestaltic pumps work is by basically squeezing the water from input to output. As a result water DOES NOT flow back into the pump from the tube.
- As RO water is pumped into the tube (that slow pump is always running) it forces water from the top of the tube to get squeezed out into a tube that then drips into my tank
What we call "kalkwasser" is a SATURATED solution of "kalkwasser powder" (Calcium Hydroxide, I believe) so basically, you can shove as much powder into the reactor as you want, since it will only dissolve up until the water is saturated, so the water that is forced from the tube is saturated "kalkwasser".
My reactor is like 4 feet tall (4 inch diameter tube) and I shove like 10 tablespoons of kalk powder into it. I replenish it when I don't see any more powder, or cloudy water at the bottom (It's made of PVC and clear acrylic). The top of my reactor is a simple rubber cap that is clamped on.
Make sense?
Basically a kalk "reactor" is nothing more than something that mixes kalkwasser powder into water and then feeds it to your tank. Now some people claim that exposure to CO2 in the air makes the kalkwasser less effective. I have no idea if that is true. That's why many reactors are airtight.
I used a plan similar to that of Bill Esposito's plans.
http://www.mv.com/users/besposito/nilsen.html
Hope that helps!
V