Cycled system. Checked heat exchanger, found some rust and corrosion. No cracks found at this time. Checked burners. Checked and cleaned flame sensor. Checked igniter, tested lower, but within normal range at this time. Checked and adjusted gas pressures to maximize efficiency. Checked ventor motor. Ok. Found some rusting under ventor motor, but no cracks in transition assembly found at this time. Checked for levels of CO and XS air in exhaust. Normal levels found at this time. No CO found in airstream. Average life expectancy for this unit is 14 years. This system is 15 years old. System is operating normal at this time, but due to age and condition, future failure is expected. Job complete. Customer has issues with how drain line from both units drained into floor drain. Added two drain elbows and small amount of drain line to drop into drain directly instead of draining on top of cap. Cut in both elbows. .