Any time a child tests positive for lead which exceeds the standards established in N.H. Rev. Stat. § 130-A:5, I, the department of health and human services shall test the water in the unit for lead. If the presence of lead in the drinking water exceeds the action level established by the Environmental Protection Agency, the landlord shall notify the tenant or prospective tenant and shall install on the kitchen faucet a filtering device certified to reduce lead by NSF International/American National Standards Institute and follow all standards for the replacement of the filtering device and cartridges. The landlord shall not be required to maintain or install water filters where the source of the lead has been removed and the water tests below the action level established by the Environmental Protection Agency, as verified by the department of health and human services.