A $1.3 million project to replace the town’s water mains is set to begin Monday. The first phase, expected to take about a month, involves the installation of new mains along the full length of Linwood Street. The second phase will be done on French, Morgan, Thornton, Walsh, and Zenas roads. The third and final phase will cover Maple Avenue and Cottage, Lynnfield, Winter, Platts, and Summer streets. Rockland-based Tom Gioioso Construction Inc. is carrying out the project, which is to be completed by the end of next May, said Noreen Jordan, administrative assistant in the Department of Public Works. The work will be carried out weekdays between 7 a.m. and 3:30 p.m. All the streets will remain open during construction, but motorists are advised to expect traffic delays.