Tankless Water Heater Repair in Carrollton and DFW
- Licensed Texas plumbers
- Gas and electric, tank and tankless
- Same-day visits when the schedule allows
Start with the symptom
A tankless heater tells you what is wrong in three ways: an error code on the remote or board, the pattern of the failure, and the sound it makes. Water that turns lukewarm, a unit that clicks and does not light, hot water that fades after a minute, or a display that flashes a number each point to a different group of causes.
| Symptom | Likely causes | First check |
|---|---|---|
| Unit clicks and never lights | Gas valve closed, low gas pressure, dirty igniter or flame rod | Gas shutoff and meter supply |
| Lights then shuts off | Dirty flame rod, blocked vent, condensate backup | Error code, vent terminal, drain |
| Lukewarm water, never hot | Scale on heat exchanger, undersized flow, crossed lines | Last flush date, flow at fixture |
| Hot water fades after a minute or two | Scale, low gas pressure, clogged inlet filter | Inlet filter and gas supply |
| Cold burst between hot water | Cold-water sandwich from short draws | Recirculation and flow settings |
| Rumbling or popping inside | Scale boiling on the heat exchanger | Descale |
| Display dead | Breaker, power cord, board fault | Outlet and breaker |
Real error codes by brand
Codes differ by brand, model and firmware, so the unit's own manual is the final reference. The codes below are among the ones the manufacturers publish and are shown here to explain the usual direction of the fault, not to encourage guesswork. A code that returns after a power reset needs a technician.
| Brand and code | What the maker describes | Usual direction |
|---|---|---|
| Navien E003 | Ignition failure | Gas valve, gas pressure, igniter, flame rod |
| Navien E012 | Flame loss during operation | Low gas pressure, dirty air intake, flame rod |
| Navien E016 | Overheat | Restricted flow, scale, vent problem |
| Rinnai 11 | No ignition | Gas supply, igniter, flame rod |
| Rinnai 12 | No flame | Gas supply, flame rod, vent recirculation |
| Rinnai 14 | Overheating | Thermal fuse, heat exchanger, board |
| Rinnai 25 | Condensate safety switch tripped | Drain line, neutralizer, condensate pump |
| Noritz 11 | Ignition failure | Gas supply, igniter, flame rod |
| Noritz 12 | Weak or lost flame | Flame rod, gas pressure, vent |
| Noritz 16 | Outlet temperature spike | Scale buildup |
| Noritz 29 | Condensate drain problem | Blocked line or wrong pitch |
Flushing and descaling in DFW water
Scale is the main wear item on tankless units in North Texas, because heated hard water leaves calcium and magnesium on the heat exchanger. Most manufacturers call for descaling at least yearly in hard water areas, and the owner's manual gives the solution and the method. A plumber with isolation valves can do it in about an hour.
- Turn off the gas and power, then close the isolation valves.
- Connect a small pump and hoses to the service ports, so a descaling solution loops through the heat exchanger.
- Run the loop for the time the manual specifies, commonly about 45 minutes to an hour.
- Flush with clean water, remove and clean the inlet filter screen, and reopen the valves.
- Restore power and gas, fire the unit and confirm temperature and flow.
Igniter, flame rod, fan and inlet filter
The flame rod senses whether burner flame is present. A thin coating of oxide or scale on it makes the board think the flame failed and shut the unit down, so cleaning the rod lightly is a standard first service step. The igniter wears and cracks over time. The fan motor can seize or run slow, which sets off vent or combustion faults.
The inlet water filter catches grit from the home supply; after plumbing work or a main break it can clog and cut flow below the minimum needed to start the burner. Cleaning it takes minutes and is worth doing every flush. When the gas supply is the issue, the pressure measured at the heater under full fire shows it.
Cold-water sandwich
What it is: hot water, a brief burst of cold, then hot again. It happens when you shut the water off for a moment and open it again; the heater has stopped, and cold water in the pipes reaches the faucet before the burner relights. Using a longer draw, a recirculation setting, a small buffer tank or adjusted flow settings reduces it. It is not a defect in itself.
When repair is not worth it
A tankless unit commonly lasts 15 to 20 years when it is flushed regularly. A unit that is badly scaled, has a cracked heat exchanger, or needs a main board and a fan on top of a heat exchanger replacement may cost more to repair than a new heater. The heat exchanger is the most expensive part, so a replacement quote that approaches half the price of a new unit points to replacement. Before deciding, compare the figures with the tankless cost page, then ask whether the original install had isolation valves, a correct gas line and a vent that meets the maker's rules.
DFW notes: freeze, power and gas
A tankless unit mounted outdoors or in an unheated garage is exposed to freezing weather. February 2021 broke inlet fittings, heat exchangers and condensate lines in many North Texas homes. Built-in freeze protection works only while power and, on gas models, the gas supply are on, which is why outages are the real risk.
Gas units need a steady supply from Atmos Energy. A heater that trips at full fire only on cold mornings may be seeing low line pressure rather than a bad part, and the pressure test shows it.
Straight answers
Why does my tankless water heater show an error code?
The control board has detected a fault, such as ignition failure, lost flame, overheating or a blocked condensate drain. The code points to a system, not always a bad part. Power cycling once is reasonable; a code that returns needs a technician.
How often should a tankless be flushed in DFW?
Once a year is the usual schedule for hard water, with a shorter interval if flow slows or the unit rumbles. Isolation valves make it a quick service. Skipping it is the most common reason for premature repairs.
How much does tankless water heater repair cost?
A typical repair costs about $200 to $900 in DFW. A flush or sensor cleaning sits at the low end, while a fan, board or igniter assembly costs more. A heat exchanger can approach the price of a new unit.
Why does my tankless run hot, cold, hot?
This is the cold-water sandwich. It occurs when water is turned off briefly and back on, and cold water already in the pipe reaches the tap before the burner relights. Longer draws, recirculation or a small buffer tank reduce it.
Can I repair a tankless water heater myself?
You can clean the inlet filter and read the code. Gas, venting and board work should go to a licensed plumber. Gas leaks and combustion faults put carbon monoxide and fire risk in the house.
Is a tankless worth repairing at 12 years old?
Often yes, if it has been flushed and the repair is a sensor, fan or igniter. A cracked or heavily scaled heat exchanger tips it to replacement, because that part costs the most. The decision hinges on the quote against a new unit.
Water heater trouble in North Texas?
Tell us your ZIP and the symptom; the rest is sorted on the call.