The town is offering more residents an opportunity to purchase discounted rain barrels. Rainwater collected in the barrels can be used for lawn watering, car washing, and other needs. In April, the Department of Public Works sold rain barrels at its Earth Day recycling event. But the unexpectedly high demand exceeded the supply, and as a result, the department purchased additional barrels. Those barrels are now available for residents to buy weekdays from 7 a.m. to 2:30 p.m. at the DPW garage, 95 Hobart St.  Barrels are $30, with a limit of three per household. Quantities are limited. The department is reminding residents that it also has compost bins for sale at the garage for $30, made available through a grant from the Massachusetts Department of Environmental Protection’s Sustainable Materials and Recovery Program.  All purchases for rain barrels or compost bins must be made by check.