Got around to doing some tests. Here is the test setup.
2 x stepper pumps for fill and reagent, 1 x std dosing pump for drain. pH probe with atlas pH circuit, diy stirrer.
Set it to do 7 test over 5 hours. Testing natural seawater. Results in dKH:
6.991
6.949
6.894
6.910
6.891
6.883
6.889
Not to bad.
There is trend that when the test
isn't run for 12 hours or more the first couple tests seem to read a little higher. Need to look into that a little further.
Very small sample size but looks promising.
Chris