Arrived on site and inspected customer installed tankless. Rinnai tankless Checked diagnostics and came back with error codes indicating incoming gas pressure issue. Inspected propane tank, customer has 3/8” regulator for camp stove on a 100 gallon propane tank. Incoming gas pressure not high enough to operate unit. Spoke with customer about findings. Customer did not want estimate. Customer would like to fix himself. Collected dispatch fee and departed. Customer satisfied with todays service.