For this job I did a tankless water heater diagnostic. We determined the flow sensor was not working and not telling the water heater to turn on. I ordered new sensor and replaced the new part. The hot water was returned back to home after the replacement of the sensor. I also completed a full tankless water heater flush/maintenance. I ran descaling solution through tankless for 1 hour to clean out the unit. I pulled filters and clean them from any debris and build up. I put tankless back together, tested and left work area clean.