Here's the thing: maintenance of existing infrastructure that serves existing residents is almost entirely paid for by astronomical "impact fees" paid by new developments. In the East Bay, 85% of EBMUD's maintenance (not capital!) budget is funded from impact fees. These can be really high. Any new dwelling in the East Bay pays a minimum of $26000 for water capacity and a minimum of $4100 for wastewater capacity. It's a big pyramid scheme and the existing residents better get a clue and permit some new construction, or the public utility districts are going to have to change their strategy and get all that money from annual assessments on existing properties.
So it delivers 97% of the product to the user. Seems pretty good. What is your standard? According to the EPA the typical water system loses 16% to leaks, that means SFPUC is well above the typical system performance.