Lennox condensing boiler maintenance. Client reported intermittent heat from hot water taps. Performed full maintenance including cleaning the boiler and heat exchanger. Attempted to remove the water inlet filter but stopped to avoid damage—recommend having a replacement filter on hand if removal is required. Diagnostics suggest the domestic hot water flow sensor may be the cause, but this cannot be guaranteed; other issues such as scale buildup in the heat exchanger may also contribute. At time of testing, both space heating and DHW were operating normally and all readings were within manufacturer specifications. We will reach out with estimate