San Diego is in the midst of spending roughly $3 billion on a massive new water treatment system, but city officials can’t or won’t tell customers how that will affect their water bills. New water recycling plants will eventually purify enough sewage to provide a third of the city’s drinking water. In November, the City Council approved the first, $1.4 billion phase of the project. Water bills will rise, that much is certain. Yet, officials in Mayor Kevin Faulconer’s administration are refusing to estimate by how much.