Performed yearly maintenance and safety checks on 2018 Bryant 80% down flow. Cleaned flame sensor. 49 ohm ignition. 23 ppm co in flu. 0 ppm co in supply. Offered tank flush for $69 while present for SCFC. CUSTOMER accepted. Flushed tank. Resupplied water to tank. Lit pilot. Purged air from water system advised air may still be in line to bathroom, once air is purged warm water will follow. Ensured Warm water flowing from kitchen sink before departure. Replaced customer supplied 213. No issues at this time.