Estimate to flush the condensation drain and remove any build up inside of the connection to heat exchanger to the condensations drain Inspected home to find no issues. All fixtures are in good condition with no leaks. Water pressure at 62psi and all toilets flush well. Tankless water heater reportedly throwing a code 90. Tested gas pressure to find it was at 6.5 “w.c. The range for the tankless is 3.5-10.5 “w.c. Talked to tech support and they suggested trying to flush warm water down exhaust vent to flush out condensation drainage system inside the tankless and if that does not work the to remove the hose attached to the back side of the condensation drain port and remove any obstructions. Flushed water down exhaust vent of tankless and removed hose to back side of condensation port to find no issues besides a little bit of grime that flushed through the system. Could not get the heater to throw a code 90. Tested. Job is completed.