Tankless water heaters, also known as on-demand water heaters, are famous for homeowners seeking an energy-efficient solution for their hot water needs. Unlike traditional tank water heaters, tankless models heat water only when needed, saving energy and space. Despite these advantages, tankless water heaters are not immune to problems. In this blog post, we’ll explore some common tankless water heater problems and provide practical solutions to help you maintain and optimize your system.
Cold Water Sandwich
Problem: One of the most frequently reported issues with tankless water heaters is the “cold water sandwich” effect. This occurs when a brief burst of cold water interrupts the hot water stream during usage. Typically, the first person to use the hot water after the heater has been idle will experience this problem. This is because tankless water heaters do not store hot water. As the system heats new water on demand, the water already in the pipes from previous use may cool down, causing a cold burst before the newly heated water reaches the faucet.
Solution:
- Install a recirculation pump: A recirculation pump works by continuously circulating hot water throughout your home’s plumbing system, meaning there is less chance for the water sitting in the pipes to cool down. When the faucet is turned on, hot water is immediately available. Recirculation pumps are particularly beneficial in homes with long distances between the tankless water heater and the point of use (like a faraway bathroom). Although installing a recirculation pump may add to your energy consumption, modern systems are designed to operate efficiently, often with timers or motion sensors to run only when necessary.
- Adjust usage patterns: Modifying your water usage behavior is another simple yet effective solution. When you turn on the hot water, let it run for a few seconds rather than turning it off immediately. This allows the tankless heater to stabilize the temperature before you start using it. Also, reducing the number of times you turn the faucet on and off can help prevent cold water from entering the flow.
- Install a small buffer tank: A buffer tank is a small insulated tank (typically 1 to 5 gallons) that stores a small volume of hot water. This eliminates the cold water sandwich by providing instant hot water before the tankless water heater thoroughly heats up. The buffer tank essentially “fills the gap” created by the delay between the time you turn on the water and the heater reaching total capacity. These tanks are easy to install and can work alongside your existing system without significantly impacting energy consumption.
Mineral Buildup
Problem: Hard water is another significant concern for tankless water heaters. Over time, minerals like calcium and magnesium can accumulate in the heat exchanger, reducing the system’s efficiency and potentially leading to damage. This buildup of minerals can restrict water flow and increase the energy needed to heat water, thus driving up energy costs.
Solution:
- Install a water softener: A water softener is a device that treats hard water by removing the calcium and magnesium ions that cause scale buildup. It uses a process called ion exchange, where the minerals in hard water are replaced with sodium or potassium ions. Installing a water softener significantly reduces the risk of mineral deposits forming in your tankless water heater’s heat exchanger. This also extends the life of your heater, prevents clogs, and ensures that it operates at maximum efficiency. While water softeners are an additional upfront cost, they can save you money on repairs or any related potential damage and extend the lifespan of your water heater and other appliances like dishwashers and washing machines.
- Regular descaling: Some mineral buildup can still occur over time, making regular descaling essential even with a water softener. Descaling typically involves flushing the tankless water heater with a descaling solution (like white vinegar or a commercial descaler) to break down and remove mineral deposits. You can perform this task yourself if your heater has easy-to-use service valves, or you can hire a professional. Most manufacturers recommend descaling your system every 6 to 12 months, depending on your water’s hardness level. This preventative measure ensures your heater maintains its efficiency and mineral content and avoids costly repairs.
- Routine maintenance: Routine professional maintenance goes beyond just descaling. A technician can inspect your system for any signs of mineral buildup, check for proper gas and water flow, and ensure all components function correctly. They can also advise on the best schedule for regular maintenance based on your specific usage and water quality, helping you avoid unexpected breakdowns.
System Overload
Problem: Tankless water heaters are designed to heat water on demand, but they have a limited capacity regarding how much water they can heat at one time. Suppose you try to run multiple appliances that require hot water applications (like a dishwasher, washing machine, and various showers) simultaneously. In that case, the system may become overloaded, leading to a drop in water temperature or a complete shutdown.
Solution:
- Upgrade to a larger unit: If your tankless water heater frequently gets overloaded, it might be a different size for your household’s hot water needs. Tankless water heaters are rated by their flow rate, measured in gallons per minute (GPM). If your household frequently uses hot water for multiple appliances simultaneously, upgrading to a larger unit with a higher GPM can ensure the system can handle the demand without sacrificing consistent water temperature. When upgrading, consult a professional to calculate your household’s peak hot water usage and recommend the appropriate size heater.
- Install multiple units: For homes with high hot water demand, installing multiple tankless water heaters in parallel is an effective solution. This configuration, known as a “multi-unit system,” ensures that no single heater is overloaded. Each unit can supply hot water to different areas of the house (e.g., one for bathrooms, one for the kitchen), or they can work together to share the load when multiple fixtures are being used simultaneously. While this is a more expensive solution, it provides an uninterrupted hot water supply and is particularly beneficial for large families or homes with multiple bathrooms.
- Stagger appliance use: A more straightforward and more cost-effective solution is to be mindful of when and how you use hot water appliances. Instead of running the dishwasher, washing machine, and shower simultaneously, try to stagger these activities throughout the day. By spreading out your hot water usage, you reduce the chances of overloading the system and maintain a steady hot water supply.
Ignition Failure
Problem: If your tankless water heater is failing to ignite, it could be due to a number of issues, such as insufficient gas supply, air supply problems, or electrical component failure. When the heater doesn’t ignite, a cold water supply is produced, which can be a significant inconvenience.
Solution:
- Check the gas supply: If your tankless water heater runs on gas, ensuring a sufficient gas supply is crucial for ignition. First, check that the gas valve is fully open and that there is adequate gas pressure. Sometimes, a low or interrupted gas supply can cause ignition failure. If you have other gas appliances in the house, see if they work properly. If they do not, there may be an issue with your gas provider, and contacting them can help resolve the problem.
- Check for venting issues: Proper ventilation is necessary for your tankless water heater to function efficiently and safely. If the exhaust or intake vents are blocked, the heater may not ignite as a safety precaution. During colder months, blockages can occur from debris, such as leaves bird nests, or even ice. Inspect the air intake and exhaust pipes regularly and clear any obstructions. Proper venting system installation is also essential to ensure safe and effective operation. If you suspect poor vent installation, consider having a professional inspect and correct it.
- Inspect electrical components: If your tankless heater is not igniting, there could also be an issue with the electrical system. Check the circuit breaker to ensure it has yet to be tripped. If your unit uses an electric ignition, inspect the wiring and fuses to see if they function correctly. A malfunction in any electrical component, such as the thermostat or sensors, can also prevent ignition. If you are unsure about inspecting these components, it’s best to call a licensed professional technician to handle the electrical work safely.
Fluctuating Water Temperature
Problem: Some homeowners report inconsistent water temperatures with their tankless water heaters, where the water may go from hot to cold and back to hot again during use. These fluctuations in water temperature can be frustrating, especially in the middle of a shower.
Solution:
- Check for low water pressure: Tankless water heaters require a certain amount of water pressure to operate correctly. Low water pressure can lead to inconsistent hot water temperatures. Measure your home’s water pressure and make sure it is within the recommended range for your heater, typically between 30 and 80 psi. If your heating water pressure is too low, you may need to install a pressure regulator to ensure a stable water flow.
- Clean or replace the filter: Many tankless water heaters have inlet filters that can become clogged over time. These filters trap debris and sediment, leading to insufficient water flow and causing the heater to struggle to maintain a consistent temperature. Regularly cleaning or replacing the filter per the manufacturer’s instructions can help improve the water flow.
- Adjust temperature settings: Sometimes, fluctuating temperatures are due to incorrect water heater temperature settings. Ensure your heater’s temperature setting is not too low or too high. Most experts recommend setting your tankless water heater to around 120°F (49°C) for optimal performance. If set too high, the water heater may struggle to maintain that temperature, especially under heavy use.
- Consider a flow-stabilizing valve: A flow-stabilizing valve can help balance the water flow through your tankless heater, ensuring consistent water pressure and proper water flow and preventing fluctuations in temperature. This valve regulates the amount of water that passes through the heater, preventing it from giving out incorrect temperature settings and being overwhelmed by sudden changes in demand. Installing one can significantly improve your water temperature’s consistency and optimal performance.
Exhaust Blockages
Problem: Tankless water heaters require proper ventilation to expel exhaust gases safely. If the venting system becomes blocked or obstructed, the heater may shut down as a safety precaution to prevent carbon monoxide buildup or fire hazards.
Solution:
- Inspect and clean the venting system regularly: One of the most effective ways to prevent exhaust blockages in your tankless water heater unit is by regularly inspecting and cleaning the venting system. Tankless water heaters use proper ventilation to remove harmful exhaust gases like carbon monoxide. Over time, obstructions like debris (leaves, dirt, or bird nests) can accumulate in the venting pipes, reducing airflow and potentially leading to dangerous malfunctions. Checking the venting system for visible blockages or damages at least twice a year can prevent this issue. In areas prone to extreme weather conditions, such as snow or ice, inspecting more frequently and ensuring that the external venting outlets are clear of snow or frost buildup is essential.
- Ensure proper installation: A critical factor in preventing exhaust blockages is the correct venting system installation. Poorly installed venting can lead to improper airflow, increasing the chances of blockages. For example, vent pipes that are too long or have too many sharp bends can trap debris more efficiently. Ensure the vent pipes are installed with a gradual slope and follow the manufacturer’s specifications for the correct venting length and materials. Hiring a professional installer to verify proper installation is an excellent long-term investment to avoid future issues with exhaust blockages.
- Install a vent termination screen: Another preventive measure is to install a vent termination screen, which can help block debris and small animals from entering the venting system. These screens are typically made of stainless steel mesh, which is durable and rust-resistant. While they prevent blockages, cleaning the screen periodically is essential, as even small accumulations of dust or debris can obstruct airflow.
- Install carbon monoxide detectors: Although not a direct solution to preventing blockages, carbon monoxide detectors are an essential safety feature for any home with gas appliances, including tankless water heaters. These detectors will alert you to dangerous levels of carbon monoxide in the event of improper ventilation, warning you early of a potential blockage before it becomes life-threatening.
Error Codes
Problem: Many modern tankless water heaters have digital displays showing error codes when something goes wrong. These codes can range from simple issues like clogged filters to complex problems like malfunctioning sensors or gas valves.
Solution:
- Consult the user manual for guidance: When an error code appears on your tankless water heater, the first step is to refer to the user manual. Most manufacturers include a detailed list of error codes, explaining what each means and offering specific troubleshooting steps. For example, standard codes may indicate problems such as clogged filters, ignition failures, or sensor malfunctions. The user manual often provides easy-to-follow instructions for resolving minor issues, such as resetting the system or cleaning the filter.
- Reset the system: A simple reset can often resolve minor errors. Many tankless water heaters have a reset button or power cycling feature that allows you to restart the system and prevent temporary faults. Resetting can resolve issues like minor electrical glitches or sensor malfunctions, mainly if the heater has been used for an extended period. However, if the error code reappears after a reset, it’s a sign of a deeper issue or more than incorrect temperature settings requiring further investigation.
- Clean or replace the air filter: Many tankless water heaters have air filters that can become clogged with dust, debris, or pet hair over time. A clogged air filter can lead to error codes related to airflow or combustion problems. Regular cleaning or replacing the air filter, as recommended in the user manual, is a regular maintenance task that can prevent these error codes from occurring. Inspect the filter every few months, especially in homes with pets or dusty environments.
- Check for loose or faulty connections: Error codes related to electrical issues can often be traced to loose or incorrect wiring connections. Inspect the power supply, wiring, and fuses to ensure everything is connected correctly and intact. If you are comfortable working with electrical systems, you can tighten loose connections or replace damaged wires. However, if the issue involves internal components, such as sensors or circuit boards, it’s best to call a licensed professional to diagnose and repair the system safely.
- Call a professional if needed: If you encounter an error code that you cannot resolve through basic troubleshooting, it’s time to contact an experienced technician. Some error codes may indicate more serious issues, such as gas valve malfunctions, combustion problems, or sensor failures, which require specialized tools and expertise to repair. A licensed technician can diagnose the problem accurately and perform the necessary repairs, ensuring your system operates safely and efficiently.
No Hot Water
Problem: Perhaps the most alarming problem for homeowners is when their tankless water heater produces no hot water. This can be caused by various issues, from electrical problems to gas supply issues or component failures.
Solution:
- Check the power supply: If your tankless water heater suddenly stops producing hot water, the first thing to check is the power supply. Ensure the unit is properly plugged in for electric models and the circuit breaker hasn’t been tripped. If the breaker has been tripped, resetting it may solve the problem. For gas-powered units, ensure the ignition system’s power is functioning. Sometimes, a simple power outage or electrical fault can interrupt the water heater’s operation, so verifying the power supply is a quick and easy first step.
- Inspect the gas supply: If you have a gas-powered tankless water heater, ensure that the gas valve is fully open and that an adequate gas supply reaches the unit. If your gas stove or other appliances are also not working, it could be a sign of a more significant issue with your home’s gas supply. In such cases, contact your gas provider to resolve the issue. Additionally, check the gas pressure. Tankless water heaters require a specific pressure range to operate efficiently, and low pressure can prevent the system from producing hot water. You may need to adjust the regulator or consult a professional to verify the pressure.
- Look for error codes: If your tankless water heater has a digital display, check for any error codes that may explain the lack of hot water. Error codes related to ignition failure, gas supply issues, or blocked vents can all result in the system not producing hot water. Refer to the user manual to understand the error code and take appropriate action based on the manufacturer’s troubleshooting guide.
- Examine the water inlet filter: Tankless water heaters have an inlet filter that can become clogged with debris, sediment, or mineral deposits over time. A clogged filter can restrict water flow, preventing the heater from functioning correctly. Inspect the filter and clean it according to the manufacturer’s instructions. Regular filter maintenance ensures consistent hot water and extends the life of your heater by reducing strain on the system.
- Check for frozen pipes (in cold climates): If you live in an area with freezing temperatures, the water pipes leading to your tankless heater may have frozen. This can prevent water flowing through the heater, resulting in no hot water. Check for signs of frozen pipes, such as bulging or frost-covered sections. If you suspect frozen pipes, gently thaw them using a hair dryer or space heater. Avoid using open flames, as this can cause damage. To prevent future freezing, insulate exposed pipes and consider installing a pipe heating system.
- Call a professional technician: If you’ve checked the power and gas supply and cleaned the filter, and there are no apparent issues with the pipes, yet there’s still no hot water, it’s time to call a professional. The problem could be due to a more complex issue, such as a malfunctioning heat exchanger, faulty ignition system, or broken components inside the unit. A licensed technician will have the tools and expertise to provide tankless water heater solutions and make the necessary repairs to restore your hot water supply.
Conclusion
While tankless water heaters offer many benefits, they come with their own challenges. By understanding these common issues and implementing the suggested solutions, you can keep your tankless water heater running smoothly and efficiently. Regular maintenance, proper installation, and timely troubleshooting are crucial to avoiding major problems and ensuring that your water heater continues to provide hot water on demand for years.
If you’re experiencing ongoing issues with your tankless water heater, don’t hesitate to contact a professional plumber or technician. Expert help can easily fix many problems, ensuring your home continues to enjoy the energy-efficient benefits of on-demand hot water.
Feel free to call the professionals at Water Heater Wiz for any tankless water heater issues, or for any tankless water heater installation needs.
