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question about powder kalkwasser


Prinz

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is it normal for the water to turn milky white?

 

i have added it to my top off water with another pump as circulation to the top off

 

thank you

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Yup. Completely normal when you first mix it in.

Once the water becomes saturated, the nice thing about kalk is that the impurities settle out to the bottom as sediment.

Important not to have a circulation pump keeping it suspended all the time though. Let it settle, and don’t have the ato intake at the bottom. You don’t want to pump the sediment into the tank.




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Prinz, 

Chemically-speaking, kalk is calcium hydroxide, or lime powder. It has low solubility in water - that is, only a very small amount of it dissolves (as you noted) completely and a sediment often settles to the bottom of any container that you add it to. The level of dissolution is typically a teaspoon per gallon or less.

 

Kalkwasser is German for "limewater" and it's the slightly milky fluid that sits above the undissolved lime that settles to the bottom of a reasonably still (or only very slightly stirred) container of water and lime. Kalkwasser's concentration is very well controlled so long as you don't have a bunch of undissolved sediment suspended in the water. That's an important point to note which Sneeze has already made and I'm here just to reiterate it to underscore its importance. So, if you're stirring the container of kalk plus water with a pump, it's very likely that you'll have suspended solids, and you won't have much control over the alkalinity that you're dosing. Stir your Kalk reservoir intermittently and just enough to keep it saturated. Once a day for a moment or two is normally enough. Then, let the undissolved solids settle out before dosing your tank.

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Tom- you mentioned to stir it once a day to keep saturation levels up, could you elaborate why you feel that is important? I read an article some years ago by Randy Holmes-Farley about kalk solution, and his take was if you are using a reservoir, to leave it completely undisturbed until you need to replenish it. The idea is that once it is stirred and settled, the water is fully saturated. You can pull water from anywhere in the container and it has the same concentration - fully saturated. It only becomes less that saturated if you break the crust in the surface, allowing the kalk to react with oxygen. Now you’ll have a less that saturated solution unless it’s stirred again. So, stir once, let crust develop, don’t touch until refilling is needed. 

 

I agree, however, with not dosing the whitish water before it had settled out. 

 

At least, that’s my recollection of the article, and since I’m posting from a phone right now, I’m lazy and don’t want to try to search for it (this is long enough and my thumbs are now tired) ?

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21 hours ago, bues0022 said:

Tom- you mentioned to stir it once a day to keep saturation levels up, could you elaborate why you feel that is important? I read an article some years ago by Randy Holmes-Farley about kalk solution, and his take was if you are using a reservoir, to leave it completely undisturbed until you need to replenish it. The idea is that once it is stirred and settled, the water is fully saturated. You can pull water from anywhere in the container and it has the same concentration - fully saturated. It only becomes less that saturated if you break the crust in the surface, allowing the kalk to react with oxygen. Now you’ll have a less that saturated solution unless it’s stirred again. So, stir once, let crust develop, don’t touch until refilling is needed. 

 

I agree, however, with not dosing the whitish water before it had settled out. 

 

At least, that’s my recollection of the article, and since I’m posting from a phone right now, I’m lazy and don’t want to try to search for it (this is long enough and my thumbs are now tired) ?

Many ATO's replenish water by adding it as the kalkwasser is drawn off. It takes time for this freshwater to diffuse across the reservoir . Diffusion may be sufficient to keep the water saturated, depending upon the temperature, volume and the daily evaporation. Stiring the container for a short time ensures turnover and saturation. 

 

In Randy's case, he's said that he uses a large trashcan that he refills periodically. Thus, he makes his kalk in a single large batch, stirring it once when he makes it. In this case, the water surface is undisturbed and the crust that forms provides some protection from reacting with CO2 (not oxygen) to form calcium carbonate precipitate (which is what the crust is made of). This is different than a situation that refills the container.

 

Few people that I know use Randy's method of batching kalkwasser the way he does. Most use it in a reservoir that refills (such as with a kalkstirrer) in concert with an auto topoff system. 

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Well, I guess put me on your short list that use Randy’s batch method. I know it takes more room, but it’s safer than having it hooked up to an ATO. 

 

I assumed that the OP was batch mixing it. In either case, you’ve given a great recap of that article and the different methods involved!

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On 5/26/2019 at 2:21 PM, bues0022 said:

Well, I guess put me on your short list that use Randy’s batch method. I know it takes more room, but it’s safer than having it hooked up to an ATO. 

 

I assumed that the OP was batch mixing it. In either case, you’ve given a great recap of that article and the different methods involved!

The OP could have been doing it that way (upon re-reading his post). It sounded like he was using a Nilsen reactor when I first read it. That's really old-style, DIY-type of stuff, though.

 

Depending upon the size of the ATO, it can be a safeguard. Of course, if the ATO reservoir is large (as RHF's is compared to his system volume), a salinity crash is a more likely risk than a kalk overdose. 

 

There are ways to make kalk dosage as part of an ATO safer. Most involve peristaltic pumps and timers, and limited amounts of kalk powder, though. And safe placement of the reactor, too. (I've heard stories of people tipping their kalk reactor contents over into the sump, leading to overdoses.) Most overdose failures ultimately trace to having too much kalkpowder in whatever container you're dealing with and can be limited by limiting how much you make available to your tank. (That's ultimately what the pre-mixed reservoir model relies upon, and you can do the same thing by using a freshwater reservoir that passes water through a kalk reactor with a limited amount of kalk powder in it.)

 

Kalkwasser's a great balanced additive, but due to it's limited solubility, it can never fully meet a thriving SPS tank's calcium and alkalinity demands. You always wind up with additional supplementation such as a calcium reactor or two-part dosing. If evaporation in a tank is variable (for example, different evaporation rate in the summer versus the winter months), then dosing via kalkwasser using ATO (without a timer restriction) deliverers a dose that varies seasonally. Bruce (BBYATV on the forum) has a system where he doses kalkwasser to meet minimum evaporation demands, supplementing any additional fresh water needs with straight RO/DI. This keeps his dosage constant from day to day. My evaporation is more consistent over the year, so my system mitigates kalk overdose and salinity crash risks  by using a 1 liter per hour peristaltic pump and by limiting the volume of my ATO reservoir (which hold about 2% of my system volume). The ATO reservoir refills automatically 2x per week (again, under rate-limited and timer control).

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