Tankless Water Heater Repair
Houston's tankless water heater repair specialists. We diagnose error codes, fix ignition failures, descale heat exchangers, and replace flame rods — same-day, with OEM parts. Rinnai, Navien, Noritz & more. Call 832-673-0909.
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Expert Tankless Water Heater Repair in Houston
Why Tankless Units Fail — And Why Speed Matters
Tankless water heaters are engineered for 20+ years of service, but Houston's hard water has other plans. Mineral scale silently coats the heat exchanger, restricting flow and forcing the unit to work harder until it triggers a safety lockout. When your Rinnai flashes error code 11, your Navien shows E003, or your Noritz unit won't ignite at all — that's your system telling you it needs professional attention now, not next week.
The longer a malfunctioning tankless unit runs in a degraded state, the more expensive the eventual repair becomes. A $150 flame rod replacement today can become a $600 control board failure next month if the root cause isn't addressed. Our technicians are factory-trained on all major brands and carry the most common parts on every truck, so we resolve most tankless issues in a single visit.
Common Tankless Water Heater Problems We Fix Daily
We Solve the Issues Other Plumbers Can't Diagnose
General plumbers see a tankless error code and immediately recommend replacement. Our team sees the same code and knows exactly which component failed, why it failed, and how to fix it. Here are the most common tankless repairs we handle across Houston:
Heat Exchanger Descaling ($195–$250)
Houston's hard water creates calcium and magnesium deposits inside the heat exchanger, reducing efficiency and triggering temperature fluctuations. We flush the system with a commercial-grade descaling solution, monitor pH levels throughout the process, and verify flow rates before and after to confirm full restoration.
Flame Rod Cleaning & Replacement ($100–$175)
The flame rod confirms to the control board that a flame is present. When it corrodes or develops carbon buildup, the unit will fail to ignite or shut down mid-cycle. We clean or replace the rod with genuine OEM parts and recalibrate the ignition sequence.
Control Board Diagnostics & Replacement ($300–$600)
The control board is the brain of your tankless unit. When it fails, you may see multiple error codes, intermittent shutdowns, or complete loss of function. As authorized service providers for Rinnai, Navien, and Noritz, we stock the most common boards and can often complete the replacement the same day.
Ignition & Gas Valve Failures ($200–$450)
If your unit clicks but won't light, or lights and immediately shuts off, the issue is typically the igniter, gas valve, or flame sensor. We test each component individually to pinpoint the failure and replace only what's necessary.
Flow Sensor & Thermistor Issues ($125–$250)
Inconsistent temperatures or "cold water sandwiches" are often caused by failing flow sensors or thermistors. These components regulate water flow detection and temperature readings. We replace them with OEM parts and recalibrate the system.
our process
step 01
Call & Describe Symptoms
step 02
Same-Day Diagnostic Visit
step 03
Transparent Quote & OEM Repair
step 04
System Testing & Performance Verification
Request your free quote.
city service list
any questions?
Error codes are your tankless unit's built-in diagnostic system. Each brand uses different codes: Rinnai uses numeric codes (like 11 for ignition failure), Navien uses E-codes (like E003 for ignition), and Noritz uses two-digit codes. Rather than just clearing the code and hoping it doesn't return, our technicians trace the error to the specific failed component — whether it's a flame rod, gas valve, flow sensor, or control board — and repair the root cause.
Tankless water heater repair costs in Houston typically range from $150 to $600 depending on the issue. Common repairs include flame rod cleaning ($100–$175), heat exchanger descaling ($195–$250), ignition and gas valve repairs ($200–$450), and control board replacement ($300–$600). Our flat diagnostic fee is applied to the repair cost if you choose to move forward with the fix.
Yes. Hot Water Guys is factory-authorized to service Rinnai, Navien, Noritz, Takagi, and Rheem tankless systems. We carry the most common OEM parts on every truck and have direct relationships with manufacturer technical support teams for complex cases. Being factory-authorized also means we can process warranty claims that general plumbers cannot.
If your tankless unit is under 10 years old and the repair cost is less than 50% of a replacement, repair is almost always the better investment. Tankless systems are designed to last 20+ years, so a mid-life repair typically delivers excellent return. If your unit is 15+ years old with a major component failure (like a cracked heat exchanger), replacement may make more financial sense. We'll walk you through the math honestly — we never pressure customers into replacements.
The most common causes are ignition failure (often a corroded flame rod or gas supply issue), a tripped error code that has locked the unit out, or severe scale buildup blocking the heat exchanger. Other possibilities include a failed flow sensor that doesn't detect water demand, electrical issues, or venting blockages. Our technicians systematically test each component to identify the exact cause rather than guessing.