The Boston Water and Sewer Commission BWSC will distribute free, reusable grease can lids and information about keeping cooking fats out of household drains this weekend ahead of the Thanksgiving holiday.

The FOG— Fats, Oils Grease— campaign is aimed at preventing an annual problem: blocked sewer lines, which trigger costly public and private sanitary sewer overflows, according to BWCS officials. The Environmental Protection Agency estimates that almost half of all sanitary sewer overflows in the US result from so-called FOG buildup.

Staff from the BWSC will be reinforcing this message— and giving out thousands of grease can lids at the South Bay Stop and Shop beginning on Friday, Nov. 16, 4 – 7 p.m. They will be out there on Saturday and Sunday as well. All Boston residents can order grease lids by calling 617-989-7599, or by going online to bwsc.org