What actually fails on a tankless in Monroe
Tankless units tell you what is wrong if you read them. Nearly every call starts with an error code, and the code plus the gas supply narrows it down long before anyone needs to open anything.
The local variable is the water. Yours comes from the City of Monroe. Where that supply is soft, scale is a slower problem here than the national troubleshooting guides assume, which means a unit throwing a temperature fault in Monroe is more often a flow sensor, an igniter or a gas supply problem than the limescale everyone reaches for first.
- Ignition and flame failure codes: gas supply, igniter or flame rod before anything more expensive.
- Cold water sandwich: usually a behaviour of the system rather than a fault, and worth explaining before selling you a fix.
- Flow sensor faults: common, cheap, and frequently misdiagnosed as a failing exchanger.
- Heat exchanger: the one genuinely terminal failure, and often still under a long manufacturer warranty. We check the serial before quoting.

What Monroe itself changes
Where the heaters sit
Garage and closet in the 1990s and 2000s subdivisions. Crawlspace through the older core, where access is genuinely tighter and priced separately.
The housing in Monroe
Monroe needs two answers rather than one. 37.0% of the housing was built between 1990 and 2009, which is the standard second-heater cohort, but 25.7% predates 1970, concentrated in the historic core and the older rental stock. Those two groups want different things: the newer subdivisions are planned replacements and straightforward repairs, and the older core is emergency work, code catch-up and landlord calls.