Minimum lot area. Each lot shall be served by public water from an off-site source and shall have an area of not less than 40,250 square feet measured within 230 feet of the front street property line and a lot width of not less than 175 feet, provided, however, that on a cul-de-sac or curved street each lot shall have a frontage along the front street property line of at least 75 feet and a lot width of at least 175 feet measured along a line 100 feet from the front street property line. Wherever a lot cannot be served by public water from an off-site source, it shall have a minimum area of not less than 81,000 square feet measured within 360 feet of the front street property line and a lot width of not less than 225 feet.