A majority of the 11 San Diego Unified schools flagged in 2017 and 2018 for unsafe levels of lead in the water were explicitly promised new or improved plumbing twice in the last decade under previous local facility bond tax measures, but haven’t yet received it, district records show. Safe drinking water has become a centerpiece of the pitch for a new $3.5 billion school facility bond by San Diego Unified School District officials, who say the new tax money would ensure old pipes and lead solders contaminating water with lead would be fixed or removed.