Upon arrival performed a one system maintenance checking heating, checked all electrical, mechanical and safety components, checked gas pressures, checked heat exchanger and clean flame sensor and changed filter. Had to leave to get filter and come back. System is operating properly at this time. Homeowner also had a drain leaking under the sink, found that water was leaking from the seal of the basket strainer. With approval removed basket strainer and resealed strainer with silicone. Sink is no longer leaking at this time. Homeowner may need us to look at water softener.