Oversparging grainfather
Most of my beers where I live now have been astringent (5 or so). Some more some less. I found one of the culprits after lots of research: I have incredibly high alkalinity (400ppm CaCO3). So I have decided to mix my own water with destilled water and the usual salts. Now I am worried about oversparging. Presuming I construct ideal water and calculate my mash and sparge water using the usual method, do I still need to worry about oversparging? If so how do I go about avoiding this on the grainfather? I've never read a detailed technique anyway. Keep sampling the sparge runoff every 5 mins and test the pH using a meter?