Customer called in because of issue she had with tankless water heater that was installed on 5/12/22. Error code showed up as E788. For dip switches set to incorrect gas type. Shut gas and power off to unit. Removed cover. Checked dip switches and set them to the proper setting. Reinstalled cover. Returned power and gas to unit. Checked water temperature at nearest Faucet. Temperature was at approximately 120 for a few seconds then reduced to approximately 100. Checked kitchen faucet and found a steady 100 degrees coming from faucet. Per management shut isolation valve to recirculation system off and tested temperatures again. Same results found. Ran water into a bucket directly off water heater. Found water at approximately 120. Note: presented findings to customer and notified them that the reduction in temperature of water could be caused by a crossover in the system. Davis is scheduled to come out on Monday to perform diagnostics on recirculation line, notified customer that