Ignition failure
No gas supply, a closed valve, an undersized gas line, a bad igniter or flame rod.
Tankless repair and maintenance
Tankless Water Heater Repair San Antonio
Error code, cold-water sandwich or no ignition? An experienced local plumber can diagnose your tankless unit and get it running again.
Call (726) 268-4856- Rinnai, Navien and Rheem
- Descaling and error codes
- No obligation to hire
Last updated November 8, 2026
Hard water care
Tankless Water Heater Maintenance: Descale Tankless Water Heater Units Yearly
At a glance
- Scale from hard water is the most common cause of tankless problems in San Antonio.
- Most manufacturers recommend descaling about once a year.
- Error codes point to the failed system: ignition, flow, venting, overheating or scale.
- Call (726) 268-4856 to be connected with an independent local plumber.
Tankless water heater maintenance in San Antonio is mostly descaling. Hard water leaves calcium scale inside the heat exchanger, which restricts flow, causes overheating and shortens the unit's life.
To descale a tankless water heater, a plumber closes the isolation valves, connects a small pump and hoses to the service ports, and circulates a descaling solution through the heat exchanger for about an hour. Then they flush it, clean the inlet filter and check for error history.
Flushing
Flushing Tankless Water Heater Units in Hard Water
Flushing tankless water heater units once a year keeps scale from building up. With very hard water, or after error codes for overheating or low flow, more frequent cleaning helps.
Tankless water heater cleaning also includes the cold-water inlet filter screen, which catches sediment, and on outdoor units, checking the cabinet for debris and insects.
Troubleshooting
Instant Water Heater Repair: Error Codes and Common Faults
Instant water heater repair starts with the error code on the controller. Codes differ by brand, but they fall into a few groups.
Overheating
Usually scale in the heat exchanger. Descaling often clears it.
Low flow or no activation
A clogged inlet filter, a faulty flow sensor, or fixtures with low flow.
Venting or fan errors
A blocked vent, a failed fan motor or a condensate drain problem.
Cold-water sandwich
A short burst of cold water between uses. Normal to a degree, but recirculation or a buffer tank can reduce it.
Brands
Repair Rinnai Tankless Water Heater Problems and Rheem Tankless Water Heater Repair
Plumbers who work on tankless units usually know the main brands' codes and parts.
Rinnai
Common calls: code 11 (no ignition), code 12 (flame failure) and scale-related overheating.
Navien
Common calls: ignition and flame errors, venting and condensate issues, and recirculation pump settings.
Rheem
Rheem tankless water heater repair often involves ignition, flow sensors and scale.
Tankless error code? Get it fixed by a local plumber.
Call (726) 268-4856Service visits
Tankless Water Heater Service: What a Visit Covers
A tankless water heater service visit typically includes descaling, cleaning the inlet filter, checking the burner and flame sensor or elements, inspecting the vent and condensate drain, and reading the error history.
Each contractor sets their own prices. If you need to fix a tankless water heater with a failed part, the plumber explains the repair before doing it.
Homeowner questions
Tankless Repair FAQs
How often should a tankless water heater be descaled in San Antonio?
About once a year for most homes. Homes with very hard water or frequent overheating codes may need it more often. A water softener reduces how often it is needed.
Why does my tankless water heater go cold mid-shower?
Common causes are scale, a clogged inlet filter, an undersized gas line, or too many fixtures running for the unit's capacity.
Can I descale a tankless water heater myself?
Many homeowners do with a pump kit if the unit has isolation valves. If the unit lacks valves or shows error codes, a plumber is the better choice.
Is it worth repairing an old tankless water heater?
Often. Tankless units can last 20 years or more, and many parts such as igniters, flame rods and flow sensors are replaceable. A cracked heat exchanger is usually the point where replacement makes more sense.
Do you repair tankless water heaters?
We are a free referral service. We connect you with an independent local plumber who diagnoses and repairs the unit.
Get Your Tankless Unit Running Again
Tell us the brand, model and error code. We will connect you with an independent local plumber who can diagnose it. No obligation to hire.