Most homeowners assume that if a tankless water heater is acting up, it must be some mysterious, high-tech failure that only happens to “these new systems.” In reality, most tankless water heater repair calls come down to a handful of very predictable, very preventable issues. The technology is more advanced than a traditional tank, but the underlying problems are often basic: water quality, installation shortcuts, neglected maintenance, or simple wear and tear. Misunderstanding this leads a lot of people to panic, ignore the signs, or rush into replacing a unit that could have been repaired fairly easily.
Another common misconception is that tankless water heaters are “set and forget” appliances that never need service. In a place like Keller, TX, where hard water is a constant factor, a tankless unit is actually more sensitive to neglect than a conventional tank heater. Mineral buildup, clogged filters, and combustion issues can show up faster if the system is never flushed, checked, or professionally inspected. When All Source Plumbing is called out for tankless water heater repair, we often find that a bit of routine care earlier on would have prevented the breakdown entirely.
Understanding the most common tankless water heater issues – and how they show up in everyday use – can save you time, money, and frustration. Instead of guessing or Googling error codes at midnight, you can recognize early warning signs, know what you can safely troubleshoot yourself, and when it is time to bring in a licensed plumber familiar with tankless systems in the Keller area. The more you know about how your system behaves, the easier it is to keep hot water flowing reliably year-round.
No Hot Water Or Inconsistent Heat
Few problems feel as urgent as stepping into a shower in Keller’s winter chill and discovering you have no hot water. With tankless systems, a total loss of hot water or wildly fluctuating temperatures is one of the most common repair calls. Unlike tank heaters that store pre-heated water, tankless units heat water on demand as it flows through the heat exchanger. If something interrupts that process – whether it is fuel, flow, or sensors – the unit will either shut down or deliver lukewarm water at best.
One frequent culprit is insufficient gas supply or a gas valve issue for gas-fired tankless heaters. If the gas line was undersized during installation, the unit might work fine at low demand but fail when multiple fixtures run at once. You might notice showers that go hot-cold-hot, or the unit shutting down when someone turns on a second faucet. All Source Plumbing often finds that correcting gas line sizing or replacing a failing gas valve restores stable hot water without replacing the heater itself.
Another source of inconsistent heat is a problem with flow sensors or minimum flow requirements. Tankless heaters need a certain flow rate to “wake up” and fire the burner. If an aerator is clogged, a showerhead is low-flow to an extreme, or there is debris in the inlet filter, the heater may not detect enough water movement to turn on. This can lead to situations where some faucets get hot water and others do not. Cleaning inlet screens, flushing the unit, and checking fixtures for blockages are routine parts of a tankless water heater repair visit in Keller homes.
Electrical issues can also mimic heater failure. A tripped breaker, a loose electrical connection, or a failed ignition component on a gas unit can all result in no hot water. Homeowners sometimes assume that because the display is lit, everything electrical is fine, but many components work behind the scenes. A trained technician will test power supply, control boards, and ignition systems to pinpoint whether you are dealing with a repairable part failure or something more serious.
Error Codes, Beeping, And Lockouts
Tankless water heaters are smarter than traditional tanks, and that intelligence shows up in the form of error codes and warning beeps. Many homeowners see a flashing code on the display and immediately fear the worst. In practice, those error codes are your unit’s way of giving you a head start on repairs. They pinpoint where the problem is occurring so a plumber from All Source Plumbing can diagnose it faster and more accurately.
Error codes commonly relate to ignition failures, exhaust or intake blockages, temperature sensor issues, or flow problems. For example, codes indicating flame failure may be tied to dirty burners, low gas pressure, or a failing ignition rod. Codes for exhaust issues often point to blocked venting, improper vent installation, or even birds’ nests or debris in the vent termination. In Keller, where seasonal storms and wind can blow debris into outdoor terminations, these vent-related codes are not unusual.
Homeowners sometimes try to clear codes by repeatedly resetting the unit or cycling power, hoping the issue will disappear. While a one-time glitch can occasionally be resolved this way, persistent codes usually signal a real underlying problem. Ignoring them or forcing the unit to restart without fixing the cause can lead to bigger damage, such as overheating, cracked heat exchangers, or melted wiring. Treat error codes as a diagnostic clue, not an annoyance to bypass.
When All Source Plumbing responds to error-code calls in Keller, we not only clear the current issue but also look for contributing factors: is the combustion air adequate, is the venting correctly sloped and secured, are there signs of moisture intrusion or corrosion? This broader view helps prevent the same error from returning a few weeks later. Properly interpreting codes and pairing them with a full inspection is a key part of reliable tankless water heater repair.
Mineral Buildup And Hard Water Damage
Hard water is a quiet troublemaker for every water heater in North Texas, but tankless units feel the impact even faster. Keller’s mineral-rich water leaves calcium and lime deposits inside the narrow passages of a tankless heat exchanger. Over time, this buildup restricts water flow, forces the unit to work harder, and reduces its ability to transfer heat efficiently. You may notice longer waits for hot water, lower water pressure on the hot side, or strange noises such as whistling or kettling.
Mineral scaling does more than just slow things down. It can create hot spots on the heat exchanger where heat cannot dissipate properly, increasing metal stress and the risk of premature failure. Sensors and temperature probes can also get coated with minerals, leading to inaccurate readings and erratic temperature control. In many Keller homes where regular maintenance has been skipped, All Source Plumbing finds significant scale buildup as the root cause of repeated error codes and shutoffs.
Descaling or flushing a tankless water heater is a critical maintenance and repair procedure. Using a pump, hoses, and a descaling solution, a plumber circulates cleaner through the unit to dissolve accumulated minerals. For systems that have gone years without service, this process can dramatically improve performance, lower noise, and reduce the occurrence of overheat-related shutdowns. Once the unit is cleaned, it often makes sense to schedule annual or semi-annual flushes depending on your water hardness and usage.
Some homeowners in Keller choose to pair their tankless heater with a water softener or a whole-home conditioning system to slow down scale formation. While that is not mandatory, it can extend the life of the heater and reduce repair frequency. Whether or not you install additional treatment, recognizing that hard water is not just a cosmetic issue but a mechanical one helps you prioritize regular tankless maintenance as a form of protection for your investment.
Ventilation, Combustion, And Safety Concerns
Gas tankless water heaters rely on a precise balance of fuel, air, and exhaust to operate safely. Problems with venting or combustion are some of the most serious issues a technician can encounter. Improper vent installation, blocked intake or exhaust, or insufficient combustion air can all trigger error codes, shut the unit down, or in worst-case scenarios, create a carbon monoxide risk. Unlike some minor issues, ventilation concerns are not DIY territory and should be handled promptly by a licensed professional.
In Keller, many tankless units are installed on exterior walls or in garages. Over time, wind-driven debris, leaves, or even insect nests can partially block vents. Homes that have undergone remodeling or attic work can also end up with crushed vent pipes or disturbed terminations. Symptoms may include error codes related to airflow, burner flame irregularities, or the unit shutting down under high demand. All Source Plumbing technicians are trained to inspect vent routing, verify clearances, and ensure joints and seals are intact.
Combustion issues can also stem from dirty burners, misaligned gas pressure, or aging components. Soot buildup, yellow or unstable flames, or scorch marks near the burner compartment are warning signs that combustion is not clean. This not only reduces efficiency but can also damage internal parts and create unsafe operating conditions. During a repair visit, a thorough combustion check includes inspecting burners, verifying gas pressures, and confirming that the unit is pulling in adequate fresh air.
Many modern tankless water heaters have built-in safety mechanisms that shut the system down when they detect dangerous conditions. While this can be frustrating for a homeowner suddenly without hot water, it is an important safeguard. The right response is not to bypass or disable these protections, but to let a professional diagnose why the safety system activated. Addressing ventilation and combustion problems correctly helps keep your home safe while restoring reliable hot water.
Leaks, Corrosion, And Component Failures
Even tankless water heaters, with their compact, on-demand design, are not immune to leaks. While they do not store large volumes of water like traditional tanks, they still contain pressurized water lines, connections, and internal components that can fail. Small leaks inside the unit’s casing can go unnoticed for a while, slowly damaging electronic boards, wiring, and metal surfaces. By the time water is visibly dripping, there may already be corrosion or electrical issues developing.
Leaks can originate from loose fittings, failed gaskets, cracked heat exchangers, or even from external piping connected to the unit. In Keller homes, temperature swings and shifting foundations can contribute to stress on plumbing connections. When All Source Plumbing inspects a leaking tankless unit, we trace the moisture back to its source, determine whether the leak is from a repairable component, and assess any secondary damage. In some cases, a simple fitting replacement solves the problem; in others, extensive corrosion may push the system closer to replacement.
Component failures are another reality as tankless units age. Flow sensors, temperature sensors, control boards, and fans can all wear out over time. One failed part can cause a cascade of symptoms, from inconsistent temperatures to complete shutdown. Because these components often work in coordination, accurate diagnosis is crucial. Swapping parts at random is not only expensive but can also introduce new issues if incompatible or low-quality components are used.
When considering repair versus replacement of a leaking or failing tankless heater, age and maintenance history matter. A relatively young unit with an isolated part failure is usually worth repairing. A much older unit with multiple corroded parts, repeated breakdowns, and a history of neglected maintenance may be better replaced. A trustworthy plumber will walk you through the pros and cons rather than pushing one option. And if your leak is related to broader plumbing or foundation movement, services such as Foundation leak repair may also need to be part of the long-term solution.
Prevention, Maintenance, And Local Expertise
Many of the common tankless water heater issues in Keller homes are preventable with consistent maintenance and early intervention. Flushing the unit to remove scale, cleaning inlet screens, checking vent terminations, and verifying gas pressures are not luxuries; they are essential tasks that keep the system running within its design limits. Skipping these steps often turns a simple maintenance visit into an urgent repair call months or years down the line.
Homeowners can take a few basic preventive steps themselves, such as periodically checking for visible leaks, listening for new noises, and noting any changes in hot water performance. If you see an error code, write it down or take a photo before resetting the unit. This information helps your plumber diagnose the issue more quickly. Avoid opening sealed compartments or attempting gas or electrical repairs unless you are properly trained; the cost of a professional visit is far less than the risk of damaging the unit or compromising safety.
Working with a local, experienced plumber is especially valuable for tankless systems. All Source Plumbing understands how Keller’s water quality, climate, and housing styles affect tankless water heaters in real-world conditions. That familiarity means faster diagnosis, better recommendations, and repair strategies tailored to how people in this area actually use hot water. Whether you have a busy household with multiple showers running at once or a smaller home with a single bathroom, the repair approach can be adjusted accordingly.
Ultimately, treating your tankless water heater as a long-term appliance rather than a disposable gadget changes how you respond to problems. Instead of waiting for a complete breakdown, you can schedule regular checkups, address minor issues promptly, and plan ahead for eventual replacement when it makes financial sense. With the right care and local expertise, a tankless water heater in Keller, TX can deliver efficient, reliable hot water for many years.
Frequently Asked Questions
Why does my tankless water heater keep shutting off during a shower? Frequent shutdowns during use usually point to one of three issues: insufficient gas supply, restricted water flow, or overheating due to scale buildup. If the unit is not getting enough gas, it may work at low demand but shut down when flow increases. Clogged inlet filters, aerators, or showerheads can cause the flow sensor to misread or drop below the minimum needed to keep the burner running. Mineral buildup on the heat exchanger can cause hot spots and trigger overheat protection. A professional inspection from a plumber familiar with tankless systems in Keller can identify which of these is causing your shutdowns and correct it.
How often should a tankless water heater be flushed in Keller, TX? In areas with hard water like Keller, most manufacturers and plumbers recommend flushing a tankless water heater at least once a year. If your water is particularly hard, or if your household uses a large volume of hot water, a flush every 6 to 9 months may be beneficial. Flushing removes mineral scale from the heat exchanger and internal passages, helping maintain efficiency and preventing overheating and error codes. Skipping this maintenance can shorten the life of the unit and increase the likelihood of costly repairs later.
Are tankless water heater repairs more expensive than tank heater repairs? Individual parts for tankless water heaters can be more specialized and sometimes more expensive than parts for standard tank heaters. However, tankless units are designed with replaceable components, which means you can often fix a specific issue without replacing the entire system. Over the lifespan of the heater, regular maintenance and timely repairs can keep costs reasonable. When All Source Plumbing evaluates a repair in Keller, we compare the cost of the fix with the age and condition of the unit to help you decide whether repair or replacement is the better long-term value.
Can I troubleshoot tankless water heater problems myself? You can safely check a few basic things on your own: verify that gas or power is on, reset any tripped breakers, clean faucet aerators, and confirm that vent terminations are not visibly blocked by debris. You can also note any error codes displayed on the unit. Beyond that, especially for gas, electrical, or internal component issues, it is best to call a licensed plumber. Attempting DIY repairs on combustion systems or control boards can be risky and may void warranties. A professional in Keller who works with tankless systems regularly can usually diagnose and repair the problem more quickly and safely than trial-and-error attempts.
When should I replace my tankless water heater instead of repairing it? Replacement becomes a realistic option when your tankless water heater is nearing or past its expected lifespan, typically 15 to 20 years with good maintenance, and you are facing major repairs such as a cracked heat exchanger or extensive corrosion. If the unit has a history of frequent breakdowns, significant mineral damage, or multiple failing components, the cost of ongoing repairs may approach or exceed the price of a new system. A trusted plumber will evaluate the unit’s age, condition, and repair history and give you clear guidance on whether another repair is sensible or if it is time to invest in a modern, more efficient replacement.