Tankless Water Heater Repair
That blinking error code is your unit telling you exactly what's wrong — in a language most homeowners were never taught. We speak it fluently across every major brand, and most repairs put a fundamentally sound unit back in service for years.
A Tankless Failure Always Has a Specific Cause
Tankless units are honest machines. Unlike a tank quietly rusting from the inside, a tankless heater self-monitors dozens of conditions — flame, flow, exhaust, temperature at multiple points — and shuts down with a specific code the moment one goes out of range. Ignition failures point to gas supply or a fouled flame rod. Overheat codes point to scale choking the heat exchanger. Flow errors point to a sensor or an inlet screen full of sediment. The code narrows the suspect list before we even open the case.
The pattern behind most local repair calls is worth naming: mineral scale. Hard well water is common from Kendall to Conway, and a tankless unit that's never been descaled is running its heat exchanger inside a slowly tightening jacket of minerals — the root cause behind temperature swings, gradual capacity loss, and eventually those overheat shutdowns. The encouraging part: scale-related problems caught before the exchanger is damaged are fully reversible, and a repaired, descaled unit with a maintenance plan often runs another decade.
Tankless Repair Rewards Specific Experience
Every manufacturer implements its own error codes, control logic, and part designs — a code 11 doesn't mean the same thing on two different brands, and a technician working from tank-heater instincts can spend your money learning that. Effective tankless repair means arriving with brand-specific diagnostic knowledge, testing components in the sequence the fault tree actually calls for, and knowing which parts fail commonly on which models. That fluency is the difference between a one-visit fix and a week of trial and error.
Codes are the map: we test in diagnostic order and replace what's failed, not what's convenient.
Gas pressure, venting, and flame quality verified — because many "unit problems" are actually supply problems.
If minerals caused the failure, the repair includes descaling and a prevention plan, or it'll be back.
When a repair approaches replacement value on an aging unit, you'll see both numbers side by side.
Why LaVergne's?
Related Hot Water Services
Whether the fix is a sensor, a flush, or a bigger conversation, these services cover every direction a tankless repair can go.
Water Heater Maintenance
Annual descaling and inspection is the cheapest insurance a tankless owner can buy. Get on a schedule and stop meeting us at emergencies.
Learn More →Tankless Water Heater Installation
When an old or undersized unit isn't worth another repair, a properly engineered replacement resets the clock for 20 years.
Learn More →Gas Leak Detection & Repair
Ignition faults sometimes trace to gas supply issues. Our gas fitters test and repair the line, not just the appliance.
Learn More →Whole House Water Filtration
If scale keeps sending you our way, treating the water solves the pattern instead of the episode.
Learn More →Water Heater Repair
Tank-style unit acting up instead? Same phone number, same-day service, every common configuration.
Learn More →Emergency Plumbing
A leaking unit or gas odor doesn't wait for business hours — and neither does our emergency line.
Learn More →Error Code Flashing? Read It to Us.
Call with the brand and code — we can often tell you what you're facing before the truck leaves the shop.
What Your Tankless Is Trying to Tell You
Short of a hard shutdown, tankless problems build gradually — and each symptom pattern points somewhere specific. The four below cover the large majority of calls we run. None of them means your unit is finished; every one of them means it's asking for attention before a small cause becomes heat exchanger damage, which is the one repair that changes the economics.
The Cold Water Sandwich
Hot, briefly cold, then hot again mid-shower. Often normal in short bursts — but worsening sandwiches point to flow sensor or recirculation issues.
Temperature Wandering
Water that drifts warm and cool under steady flow is the classic signature of scale insulating the heat exchanger.
Weaker Hot Flow Than Cold
Strong cold pressure but throttled hot means a restriction on the hot side — usually a sediment-packed inlet screen or scaled exchanger.
Ignition Clicks, No Flame
Repeated ignition attempts ending in a code point to gas supply, a fouled flame rod, or venting — a fix-today problem, not a replace-the-unit one.
Tankless Water Heater Repair FAQs
Helpful answers about Tankless Water Heater Repair from the experienced team at LaVergne's.
My unit shows an error code — should I try anything before calling?
Two safe steps: power-cycle the unit (off a minute, back on) to clear a transient fault, and confirm obvious supply basics — gas valve open, water inlet valve open, intake screen not visibly blocked with debris. If the code returns, stop there and call with the brand and code number; repeated resets against a real fault just masks the evidence we'll want.
Why does my hot water cut out mid-shower?
Usually one of three culprits: flow dropping below the unit's minimum activation rate (common with low-flow fixtures barely cracking the threshold), a scale-restricted exchanger tripping overheat protection, or a failing flow sensor misreading demand. Each has a distinct fix, and a diagnostic visit identifies which one is yours rather than guessing.
What does descaling involve, and how often is it needed?
We circulate a descaling solution through the heat exchanger via the unit's isolation valves for roughly 45 minutes, dissolving mineral buildup and restoring full heat transfer. On hard well water, annually; on treated or municipal supply, every couple of years often suffices. If your unit was installed without isolation valves, we can add them — a one-time fix that makes every future flush simple.
Is it worth repairing an older tankless unit?
Frequently yes — these are 20-year machines, and a 10-year-old unit with a failed sensor has real life left. The exception is major heat exchanger damage on an aging unit, where repair cost climbs toward replacement value. When you're near that line we show you both numbers, including what a modern high-efficiency replacement would cost after available incentives, and the call stays yours.
Do you service my brand?
We repair all major tankless brands found in local homes — Navien, Rinnai, Noritz, Takagi, Rheem, and others — including units we didn't install. Brand-specific diagnostic knowledge is exactly why tankless repair went well or badly, so it's a capability we've invested in deliberately.
Could freezing weather have damaged my unit?
It's possible if power was lost during a hard freeze — tankless units have built-in freeze protection heaters, but they need electricity to run. Units in garages and exterior walls during our cold snaps are the vulnerable ones. If yours stopped heating after an outage in freezing weather, shut off its water supply and have it inspected before running it hard; a frozen exchanger can leak once thawed.