You may want to have your system formally inspected in order to qualify for this credit.
A system is a "failed system" for purposes of the Title 5 credit when it is documented as a "failed system" after inspection by an approved System Inspector, or is determined to be a failed system by the local approving authority or the Department of Environmental Protection. See 301 CMR 15.303, 15.340.
https://www.mass.gov/technical-information-release/tir-97-12-personal-income-tax-credit-for-failed-c...
