105 CMR, § 410.190
The owner shall provide and maintain in good operating condition the facilities capable of heating water. The owner shall also provide the hot water for use at a temperature of not less than 110°F (43° C) and in a quantity and pressure sufficient to satisfy the ordinary use of all plumbing fixtures which normally need hot water for their proper use and function, unless and to the extent the occupant is required to provide fuel for the operation of the facilities under a written letting agreement. The hot water shall not exceed 130°F (54° C).
Inspection of the hot water system shall include an examination of the hot water system and its actual performance. If possible, such examination shall occur at the times and under such conditions as the occupant has identified the system to be insufficient.
105 CMR, § 410.190