A boil water advisory has been issued for customes of the Heritage Village water system in Oxford and Southbury after bacteria was detected in the system. Connecticut Water Inc. said the bacteria was detected during a routine sample, and the boil water advisory affects approximately 5,200 customers in Southbury, Oxford and a portion of Middlebury. Customers should boil their tap water before using it for drinking, cooking, food preparation, reconstituting baby formula or for any purpose where it will be consumed until further notice.