Kalwasser in ATO

mossanimal · Nov 8, 2023

How do you manage kalkwasser concentration in the ATO? My rodi reservoir never completely empties so how do I know how much to add to keep a consistent concentration? I suppose that every time it gets to the outlet I make the exact same amount of rodi every time and fill to a line and add the same amount to make up the difference.

Randy Holmes-Farley · Nov 8, 2023

mossanimal said:
How do you manage kalkwasser concentration in the ATO? My rodi reservoir never completely empties so how do I know how much to add to keep a consistent concentration? I suppose that every time it gets to the outlet I make the exact same amount of rodi every time and fill to a line and add the same amount to make up the difference.

I managed mine by measuring conductivity in the solution wen I mixed it up. I always had a bunch of solids on the bottom (mostly calcium carbonate and undissolved calcium hydroxide) and would only add more calcium hydroxide solids if I could not get the conductivity up to me target with stirring alone.

10.3 mS/cm is about saturation at 25 deg C.

mossanimal · Nov 8, 2023

Randy Holmes-Farley said:
I managed mine by measuring conductivity in the solution wen I mixed it up. I always had a bunch of solids on the bottom (mostly calcium carbonate and undissolved calcium hydroxide) and would only add more calcium hydroxide solids if I could not get the conductivity up to me target with stirring alone.

10.3 mS/cm is about saturation at 25 deg C.

Oh... interesting. From my field experience there should be a conversion from TDS to Conductivity. Maybe I can just try to maintain the same TDS? I mean... the kalkwasser is the only contribution to TDS anyway.

Randy Holmes-Farley · Nov 8, 2023

mossanimal said:
Oh... interesting. From my field experience there should be a conversion from TDS to Conductivity. Maybe I can just try to maintain the same TDS? I mean... the kalkwasser is the only contribution to TDS anyway.

There is not a single exact mathematical conversion. All TDS meters actually determine conductivity and then perform some sort of conversion to get TDS (which actually has a variety of different definitions/scales) , but regardless of that detail, one can use a TDS meter that can read in the 5,000 to 10,000 + ppm TDS range by determining what your unit reads in truly saturated kalkwasser (say, 2 teaspoons calcium hydroxide in a cup of RO/DI water) and then use that as the value for full saturation. Half that value (assuming it is not maxed out for any of the measurements) is about half saturation.