Town Meeting voters in May will be asked to approve $1.5 million to replace the 40-year-old water tank at Great Hill, said Town Administrator Paul Dawson. The price is lower than the $4 million estimated in the town’s capital planning budget a few years ago, Dawson said in a phone interview. The town has four water tanks, all of steel design, but cheaper ones may be available, he said. The lower price of a new tank came about because the town found it didn’t need one with a capacity as large as the current tank’s 2 million gallons, Dawson said. Town Meeting voters last year approved spending up to $93,000 for design and engineering costs of a new tank.