DIY Kalk Reactor
| mck > reef > equipment > kalk reactor |
When I started up the reef tank I was maintaining the alkalinity and calcium levels on a weekly basis with two-part solution. I didn't have the time or motivation to dose every night or every couple days. While this worked, it caused the alk and Ca levels to fluctuate quite a bit over the course of the week. By the time May 2007 rolled around I decided to look into kalk reactors. I didn't have the space available to have a make-up water jug or basin that could be filled with kalkwasser, so a reactor with a small footprint made the most sense to me.
There are a lot of great looking kalk reactors available on the market. In general the reactors have the sodium hydroxide (aka pickling lime) stirred up regularly by either a stir-bar (think back to highschool or college chemistry class) or a small pump on a timer. These guys are also expensive. There are DIY plans easily available for the each style, but I was looking to make something that wouldn't require another electrical outlet to be used up. I also wanted something that would take up less space in the sump cabinet.
I spent some time online looking at other prototypes and bouncing ideas off people with more experience experimenting with this than me, and came up with a solution that I had heard was popular in Japan. I would tie my kalk reactor into my automatic top-off, directly fed from my RODI unit, and use the pressure and flow of the RODI water to stir the kalk powder. No pumps, no stirbars, no big footprint.
During my design work and materials sourcing I realized that if I purchased the materials I really wanted - clear PVC pipe and fittings - I would be forced to buy them in such quantities that I could make a dozen kalk reactors. It would cost me a fortune. I did more research and found that there are a couple pipe sizes where the inner and outer diameter dimensions for standard PVC pipe and acrylic tube are almost identical. Specifically, 1-1/2" acrylic tube has almost the exact same outer dimension as 1-1/2" PVC piping inner dimension. 3-1/2" acrylic tube has the same outer diemnsion as 3" PVC pipe. I decided to check my local plastic supply houses for scrap acrylic tube, and found one that would let me buy short lengths and not by the 10' section. Perfect. I bought 10" of 1.5" tube, and 18" of 3-1/2" tube. On the way home I stopped at Home Depot and bought some PVC fittings, some 1/2" CPVC pipe, and a CPVC cement that had a high-XXXXX content. This cement would bond the acrylic and PVC well enough for my purposes.
I apologize for the clarity in the following photos, but I just took the reactor off-line and snapped some shots. Maybe the next time I refill the calcium hydroxide I'll clean the reactor and take new photos.
Kalk reactor body (Top to Bottom):
3" Clean-Out Fitting & Cap > 3-1/2" Acrylic Tube > 3" - 1-1/2" Coupler > 1-1/2" PVC Pipe > 1-1/2" Acrylic Tube > 1-1/2" PVC Pipe > 1-1/2" PVC Cap
I used the 1/2" CPVC piping and a John Guest fittings to connect to my RODI water (fed through normal 1/4" tubing) and run it to the very bottom of the reactor. I then used a shorter length of CPVC pipe at the top of the reactor, and again connected it to a John Guest fitting to run into my sump.
Here's a photo of the reactor. The 1-1/2" acrylic tube is filled with kalk powder in this photo.
Here's a close-up of the cap. Note the 2 CPVC pipes and John Guest fittings. The pipe on the left is my outlet, and the pipe on the right runs all the way to the bottom of the reactor. I had drilled holes through the PVC cap and cemented these pipes in place to make it air-tight.
Here's a close-up of the 3" - 1-1/2" coupling. I cemented the 3-1/2" acrylic tube directly into the coupling. On the bottom side, I cemented a short section of 1-1/2" PVC pipe into the coupling, and then was able to cement the 1-1/2" acrylic tube into that.
This photo of the bottom of the reactor illustrates how I cemented the acrylic tube to a short piece of PVC pipe, which was cemented to the PVC fitting (in this case, a standard 1-1/2" cap).
When my make-up water solenoid opens, the kalk powder is stirred up by the incoming RODI water. It flows upward, and the velocity of the water travelling through the 1-1/2" tube stirs the kalk up quite a bit. When it hits the 3-1/2" tube, however, it slows considerably and a very defined boundary layer develops between the turbulent kalk mix and the "saturated" kalkwasser. (Saturated in quotes because I haven't measured the reactor effluent to confirm that.) Under normal operation, the make-up only runs for a minute or two at a time, and the turbulent kalk-mix never rises more than a few inches up the 3-1/2" tube. The water at the top of the reactor, where it exits, is clear. The kalk settles quickly, and the process begins again in another hour or so.
As I mentioned, I haven't measured the pH of the kalk reactor effluent, but it seems to work great. Is the kalkwasser 100% saturated? No idea. Does it maintain the alk & Ca levels in the tank? Yup, nice and stable. Is this for everyone? No, probably not. The effectiveness of this style reactor will depend on your evaporation rate, the amount of water being made-up per cycle, the Ca & alk demands of the tank, etc. But, it seems to work for me.
Better p hotos and exploded parts diagram to come soon.