It would be nice if Kodak publishes that (and a lot more information they are hiding) on the web.(posted 8081 days ago)Calcium carbonate is not very soluble in pure water at room temperature, and that high concentration leads to another question, how low is the pH of the water. If you boil the water before mixing developer, does it solve the problem? (Much of Ca++ and Mg++ ions should form salts in solid precipitation and you'll discard them. Let them settle down in a stopped bottle overnight if necessary.) if that doesn't work, try sodium triphosphate (Calgon) or Na2H2-EDTA after removing a chunk of the inorganic metals by boiling. Water boiler usually has to deal with this problem, so your hot water tap may contain less inorganic mineral components than cold tap water.
If the pH is also affected, you might have much better luck with well buffered formulae, like D-76d, XTOL or Ilford Microphen. If the low pH is due to carbonic acid or other dissolved gas, boiling should help here again, because the solubility of gas decreases as temperature goes up.
I live near Boston and have never had problem with tap water though I use activated charcoal filter for drinking and cooking.
Ryuji Suzuki JF7WEX