Mass. Gen. Laws ch. 142 § 11
The said inspector of buildings, if any, otherwise the board of health, of each city and town, shall, within three months after it becomes subject to sections one to sixteen, inclusive, appoint from the classified civil service list one or more inspectors of plumbing and one or more inspectors of gas fitting, who shall, in the case of the inspectors of plumbing, be practical plumbers and shall have had practical experience either as master or journeymen plumbers, continuously, during five years next preceding their appointment and in the case of inspectors of gas fitting, be practical gas fitters and shall have had practical experience either as master or journeymen gas fitters, continuously, during five years next preceding their appointment; provided, that any time spent in wartime service as defined in clause Forty-third of section seven of chapter four shall be deemed a part of the continuous practical experience so required; provided, however, that any such city or town may appoint plumbing inspectors who shall also be gas fitting inspectors. Such inspector of buildings or board may remove them subject to chapter thirty-one, and shall, subject to approval of the city council or board of selectmen, fix their compensation, which shall be paid by the city or town. Said inspectors of plumbing or inspectors of gas fitting shall inspect all plumbing or gas fitting, as the case may be, in the process of construction, alteration or repair for which permits are granted within their respective cities and towns, and shall report to their appointing power or board violations of any law, ordinance, by-law, rule or regulation relative to plumbing or gas fitting; they shall perform such other appropriate duties as may be required. The approval of plumbing or gas fitting by any inspectors other than those provided for by this chapter shall not be a compliance therewith.
In a town having a population of less than five thousand persons the appointment of a plumbing inspector shall be exempt from the provisions of chapter thirty-one.
Mass. Gen. Laws ch. 142, § 11