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  1. #1
    Senior Member tang_man_montreal's Avatar
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    Jun 2003

    DIY Nilsen Kalk Reactor

    Ok, the whole instruction set is available at this site:

    However, being that the internet is what it is, and sites come and go, I will post the whole DIY article here.

    DIY Nilsen (Kalkwasser) Reactor
    Copyright © 2000-2001, Bill Esposito, All Rights Reserved.


    Bill Esposito

    I seem to be getting lazier by the day. First I bought a pH probe so I wouldn't have to keep checking my pH. Then I set up my two Tap Water Purifiers to output into a 35 gallon can so I wouldn't have to make DI water once a week. Then I bought a Reef-Filler top off pump so I wouldn't have to manually replace the evaporated water daily. Then I started dosing b-ionic because I didn't want the hassle of dripping kalkwasser. And now I've constructed a Nilsen Kalk reactor so I don't have to dose b-ionic. The next step will be to buy a Lazy Boy Recliner to place in front of the tank!

    I'm not going to detail the plans as they are available on the Web at
    but I will give you some insight into the problems I encountered building it and as to it's performance. Below is a picture of my reactor in action. The differences in my version will be described below:

    I suggest you also read the article by Nicolas Will which explains why this method for dosing kalk is a good idea.

    So let's start with the construction, or more accurately, the procurement of material. The reactor body really needs to be constructed of clear tubing so that you can see what's going on and when it's time to add more kalkwasser. The use of 4" clear PVC will allow for the easiest construction because it is physically compatible with the PVC pipe fittings you will also need to use. The problem with 4" clear PVC is the price, figure on about $20/foot for it and you will need 2 feet. I found 4" clear acrylic tubing at
    Aquatic Eco-Systems for around $9.75/foot. Acrylic is much clearer (clear PVC has a blue tint) but is harder to glue. I found that for low pressure applications that you can use Home Depot's PVC/CPVC/ABS cement and primer. I have my reactor located about 50' from my sump on the same floor so even though the tubing does run both above and below the sump level in it's circuitous route to my sump, the head pressure isn't too much and I could use that cement. Be careful with the primer because it will etch the acrylic if it's is dripped onto it, which is another indication that the cement is creating a chemical bond between the materials. If your setup requires high pressure than Weld-On #40 2 part cement is the ticket. Of course if you opt for the clear PVC than regular PVC cement will work. I used a hacksaw to cut my Acrylic tubing into 6.5" long and 13" long pieces

    The second difficult item for me to find was the plastic tubing to be used in the recirculating pump assembly. I could not find small diameter plastic tubing anywhere near where I live so I settled for 5/8" O.D. (1/2" I.D.) CPVC tubing from Home Depot. It was a little larger than I originally desired but ended up working fine. Drilling the holes for the 5/8" O.D. CPVC was somewhat of a problem. First off, I was lucky enough to be able to borrow a 5/8" drill bit as the cheapest I found one for was almost $16 at Walmart. Next, be careful drilling if you are using the acrylic instead of the PVC. Make sure the glue is thoroughly cured and go very slow. If your drill bit is new consider dulling it a bit by drilling into some steel first. You will find that you cut right through the PVC but going through the acrylic is another matter. Go slow, in short bursts, and cool it with water if you can. Also, be careful not to elongate the holes in the PVC while you're drilling through the acrylic. Since we are talking about the recirculating pump assembly , I used a Maxi Jet 250, 67 gph power head, and restricted the input by almost 50% to slow it down even more. The object of the recirculation pump is to stir up the kalkwasser without causing it to mix in with the upper saturated (clear) portion of the reactor reservoir from where the output effluent is drawn. I felt that the brand new maxi jet was just a little too powerful and hence I restricted it. The pump only has to be run a few minutes at a time 4 to 6 times a day so this should not be a problem in the long term.

    Next were the 4" PVC pipe fittings, all of which were procured at Home Depot. A standard 4" slip coupling, a domed end cap, a clean-out cover and thread collar, and a toilet closet plate to use as a stand. As suggested in the plans, I cut the end cap leaving about 3/4" for the gluing surface, and used the part I cut off to glue to the closet flange, and then to the end cap, to form a stand. You will have to bevel the piece cut off the end cap to enable you to have enough contact area with the end cap for a strong cemented connection. The slip coupling and clean-out collar were attached unmodified but I should speak a little more about the clean-out. I really wanted to find a cover which had a o-ring seal like the one that is depicted in the plans but couldn't find one. The clean-out does work but I have to use 2 or 3 layers of teflon tape every time I close it in order to make a good seal. Another modification I made was to drill a hole and glue a piece of rigid airline tubing to the center of the clean-out cap itself to create a nipple. Attached to the nipple is a piece of flexible airline tubing and a plastic air valve. Since this is the highest point in the Reactor it is used to bleed out any air trapped when you replenish or service the reactor and to bleed off pressure when you are about to open it. A reminder while I'm talking about opening up the reactor, don't forget to insert a check valve in the outlet line so that when you do open the reactor, all the water in the output tubing and sump doesn't come rushing out all over the floor.

    The last modification I made to the design was the water inlet and outlet to the reactor. Since my Reef-filler used 3/8" I.D. tubing I wanted to make the inlet and outlet that size. I also did not want the nipples for them to be on the cap as in the plans. What I did was purchase 2 polypropylene 90 deg 1/2NPTx3/8" barbs. I drilled and tapped a hole in the side of the clean-out collar for the output and the side of the bottom end cap for the input. These locations have worked fine. You can also find the barbs in larger or smaller sizes to fit your need.


    Clear 4" Tubing (2 ft) $17(Acrylic) $44(PVC)
    4" pipe fittings, cement,
    1/2"CPVC(5/8" O.D.), barbs $22

    Maxi Jet 250 $15

    1/2"NPT Tap $7

    hose clamps and
    misc tubing $5

    3/8" check valve $2.50

    rigid airline tubing
    and valve $4
    _____ _____
    TOTAL $65.50 $99.50


    I connected the input and output lines to the reactor and filled the chamber with almost 2 gallons of DI water and 3 heaping teaspoons of kalkwasser. Next I put teflon tape on the threads of the cover, wrapping the threads 3 times with the tape, and then screwing on the cover. I turned on the Reef-filler just long enough to bleed the air out of the reactor and then turned it off. Since the water in the reactor was very cloudy caused by the initial filling, I let things stand for about 4 hours before turning on the system so I would not be pumping un-dissolved kalk into my sump. I guess now is the time to talk about the mixing pump timer. The kalk requires stirring about 4 to 6 times a day and really only for about 5 minutes each time. I used a $5 timer I got at Home Depot for this purpose. I just happened to have extra on/off tabs from my 2 other timers which I use for my lights so I was able to get away with using a cheap timer. You will have to find a timer which allows for at least 4 on/off cycles a day. The shortest duration that my timer will turn on for is about 20-30 minutes so that's what I use, 4 times a day.

    Once I turned on the system, it was a hands off operation. After a few days my DKH was about 9.6 and Calcium was about 350. I then increased the amount of kalk input to my tank by increasing the evaporation rate, and then adjusting the Reef-filler to catch up with the new rate.

    One concern I have is that the pH is up, ranging from 8.4x to 8.5x. I will keep monitoring it and let you know if it continues to rise or stabilizes out.
    I am Homer of BORG... Prepare to be..OOOO!! DONUT!!!!!!

  2. #2
    Senior Member tang_man_montreal's Avatar
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    Jun 2003

    PROGRESS: ** Updated 2/13/00 **

    It's been about 2 weeks now since I started using my reactor. I'm a little disappointed about the readings I getting but others who know more than I say that they are good for just using kalk. My dKH is 9.8 and my Ca is 380-390 according to my Salifert test kits.

    As for problems with the reactor itself, the only annoyance is that as mentioned earlier, the cap is hard to seal. Often times this means a few drops a day making it to the floor. I've placed a plastic plate under the reactor to collect this excess. I plan on trying Teflon paste as it's supposed to seal better and is also supposed to be reef safe.

    Also, I have not been able go get more than about 5 days before recharging, I was hoping for a minimum of 7. I must say that I have not experimented much with the amount of kalk I charge the reactor withąsomething I will start doing next week. ** UPDATE ** I can now easily get 7-10 days out of the reactor. My next goal will be 14. I think another spoon of Kalk will do that. This may all be for naught because I've just ordered some pickeling lime, $1.49/lb vs $9/lb for kalk, so I may be in for some more experimentation. I'll let you know how it works out.

    pH continues to be somewhat high ranging from 8.30 to 8.56. I noticed that if I recharge before it's time my ph increases a point to 8.4 - 8.66. It is possible that adding more kalk before it's depleted and not letting it sit for a few hours causes a more milky effluent to get to the sump. Or, it means I need to increase the initial charge to better saturate the reactor, which may result in both longer times between recharge and higher Ca readings. One installation task I performed was to allow the output tubing fron the reactor to rise straight up to around 6 feet before turning and heading for the tank. This allows for 6 feet of settling which I think keeps the undisolved kalk out of the sump. ** UPDATE ** It seems that my pH meter went out of cal DOH! A recal brought my pH range between about 8.28 and 8.49.

    Another thing I've discovered is that I can tell when it's time for a recharge without looking at the reactor. All I have to do is look at my Pinpoint pH meter. My pH will drop a full point when the reactor effluent drops below a pH of 12. So if I get up in the morning and my pH is 8.20 I know it's time to recharge the reactor and if it's 8.3 when I get home from work it's time to recharge. This means that if you have an accurate way to measure pH you can probably get away with using only plain white PVC in your reactor and saving the cost of the clear pipe.

    Just thought I'd give you a short update on my Reactor. It's still working fine and after almost 4 months of use I took it apart to give it it's first cleaning.

    To my suprise it really didn't need any cleaning, nothing was clogged, no kalk buildup, and most suprising was that the Max-Jet 250 powerhead was clean, and looked brand new. The 4 months of use where it circulated the Kalkwasser solution 6 times a day had absoultly no effect on the pump or

    Also, I have switched to Mrs Wages Pickeling Lime with no noticable affects. Here's what Craig Bingman has to say about it.

    Craig Bingman wrote:
    "Mrs. Wages is FCC grade (Food Chemical Codex) lime. It is probably as good a grade as most of the calcium hydroxide on the aquarium market. The aquarium lime products hold their sources and the grade used pretty close to their chest. ;-)"

    "Since Ms. Wage's lime is seasonal in nature, by this time of year, it has been sitting on the shelves for at least six months. So it may have absorbed some carbon dioxide from the atmosphere by the time you use it. Conesquentially, when I use food grade lime, I use more to be sure that I get a saturated limewater product. Given how inexpensive the food grade lime is compared to aquarium lime, there isn't much financial penalty to using a little extra."

    "For that matter, one never knows how long that lime has sat on the shelf at the fish store, either. One additional comment. The food grade limes that I've seen appear to be A bit more coarse than the product from TLF. That meAns that the TLF lime will dissolve somewhat more rapidly then the food grade limes you get from the supermarket. That is a desirable property, especially if people want to mix lime with minimal effort. As in they might prefer their limewater "shaken, not stirred.""

    "Because I found phosphate rejection more efficient when limewater was vigorously mixed and then allowed to stand overnight, the particle size issue isn't that big a deal for me, but it might be for individuals who go to lesser lengths to make a saturated solution.


    *UPDATE* June 00
    I've switched back to ESV kalk in June of 00. As Craig states above, the lime is more course that the ESV Kalk and because of that, I went through 2 impellers on the maxijet in a couple of months since starting the lime. As I type this update it is now 20 Oct 00 and the Maxijet wear is back to normal, which is no wear from the ESV kalk.

    *UPDATE* Nov 01
    Reactor still working great. Using ESV kalk and current readings are Ca at 500+ and dKH at 13.6

    Who said you couldnt use PVC cement
    I am Homer of BORG... Prepare to be..OOOO!! DONUT!!!!!!

  3. #3
    Senior Member tang_man_montreal's Avatar
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    Jun 2003
    I am Homer of BORG... Prepare to be..OOOO!! DONUT!!!!!!

  4. #4
    Senior Member tang_man_montreal's Avatar
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    Jun 2003
    Nilsen Kalk Reactor PARTS LIST

    You can get the clear 4 1/2 acrylic from AES:

    AES (

    AES says the acylic tubing is 4 1/2" in diameter and fits perfectly in 4" PVC fittings (e.g. coupler, slip end and slip-threaded male). I used regular purple primer/PVC cement on everything with no problems at all. Some acrylic folks recommend WELDON 16 which would work as well.

    Used 1/4 poly tube since it is resistant to the high pH of kalkwasser (pH=12) and is cheap. I prefer Jaco connections and tap'ed them directly into the PVC since it looked nicer. [1/4-18 NPT tap using 7/16 drill].

    Maxijet is a perfect pump for this application because it can handle being turned on/off like a wave maker. Also, the 5/8 and 1/4 pump connectors are easy to adapt to using standard 1/2 ID riser pipes. Simply epoxy'ed risers to the PVC coupler, then used standard 1/4 and 1/2 hose and stainless hose clamps to attach pump.

    Yes, just a threaded cap on top. Here's roughly the inventory, but I won't tell you step by step how to do it because others have and that would take all the fun out of it. VBG

    Make sure bottom slip end cap is ROUNDED so CaOH doesn't solidify in the corners. to route input water to bottom of reactor simply epoxy 1/4 poly tube to Jaco connection taped into the threaded end cap.

    NOTE 1 - Make sure you manually prime the reactor before turning on the dosing pump otherwise the back pressure might be too great.

    NOTE 2 - Make sure the output is on the very top of the reactor to ensure that there is no hidden pockets of air that would contribute CO2 and make it harder to inject water into the reactor. Also, the dosing line should come from near the top to reduce backpressure; unless you have a very powerful dosing pump.

    NOTE 3 - Allow pipe joints to fully cure (24 hours) before drilling into them lest the joints come separate. Also, run tap water through reactor before filling with CaOH to remove as much of the dirt, unreacted glue and any pvc turnings.

    1 - 24 inch 4 1/2 acrylic tube from AES
    1 - 4" PVC coupler
    1 - 4" slip end cap (ROUNDED!)
    1 - 4" threaded end cap (ROUNDED!)
    1 - 4" toilet (ABS) thingy for use as base
    2 - 1/2"ID 2" long riser for pump
    1 - Maxijet 500 (100 GPH)
    1 - 20 foot of 1/4 poly tube
    2 - Jaco connectors (male threaded)
    1 - purple primer
    1 - PVC cement
    1 - epoxy (that will work on plastic) or WELDON 16
    1 - misc 1/2" id risers, elbo needed to route pump output to bottom of reactor

    1 - diaphram dosing pump; I used an old spectrapure litermeter
    Initially set to 1.5 liters per day.
    1 - timing device; I used X-10 appliance controller and Neptune
    I am Homer of BORG... Prepare to be..OOOO!! DONUT!!!!!!

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