"Common area", any portion of a building with more than 1 dwelling unit that is not incorporated within a dwelling unit.
"Customer service charge", a fixed amount charged by a city or town or water company for providing water to a building.
"Dwelling unit", any house or building, or portion thereof, that is occupied, designed to be occupied, or is rented, leased or hired out to be occupied, as a home or residence of one or more persons.
"Landlord", the owner, lessor or sublessor of a dwelling unit, the building of which it is a part, or the premises wherein a customer receives water service through metered measurement.
"Submetering", use of a meter by a landlord who receives water from a water company, which meter measures water supplied to a dwelling unit to enable the landlord to charge the tenant of the dwelling unit separately for water usage, or which meter measures water supplied to a common area.
"Water company", a company, as defined in section 1 of chapter 165 or a municipal utility or any other waterworks system owned, leased, maintained, operated, managed or controlled by any unit of local government under any general or special law, which company, utility or system supplies water to a landlord through metered measurement. Any landlord imposing charges on tenants or otherwise engaging in any activity permitted under this section shall not be deemed thereby to be functioning as a water company as defined herein or to be subject to any laws or regulations regulating any such company.
"Water conservation device", for all showers, shower stalls, shower compartments or shower baths, a low-flow showerhead which shall have a maximum flow rate not exceeding 2 1/2 gallons of water per minute, for all faucets a maximum flow rate not exceeding 2 and 2/10 gallons of water per minute and for all water closets, ultra-low-flush water closets not exceeding 1 and 6/10 gallons of water per flush, contained within a dwelling unit.
Mass. Gen. Laws ch. 186, § 22