Homeowners choose tankless systems for their efficiency and on-demand performance, but like any appliance, they occasionally experience issues. When there's no hot water from your tankless water heater, it can be frustrating, inconvenient, and sometimes even difficult to diagnose without help.
Why Is My Tankless Water Heater Not Heating?
While tankless systems are known for their reliability, issues can arise, resulting in a lack of hot water. However, many of these issues are fixable, and some can even be prevented.
Here are some of the most common reasons your tankless water heater stopped working or isn't producing hot water consistently.
Lack of Power or Gas Supply
If you're not getting hot water from your tankless water heater, start by checking the basics. Power and gas interruptions are common culprits. For electric tankless water heaters, a tripped breaker or unplugged unit could be the issue. For gas-powered models, the gas valve may be turned off or the line may have a blockage.
Mineral Buildup and Scaling
Hard water is a tankless unit's worst enemy. Over time, mineral buildup (especially calcium and magnesium) can clog the heat exchanger, preventing it from properly warming the water. This is one of the most common long-term tankless water heater problems we see in the Atlanta area.
Overloaded System
Tankless systems heat water as it's needed, but they have limits. If you're running multiple hot water sources, such as a shower, dishwasher, and laundry machine, all at once, the system may struggle to keep up. This can result in lukewarm or cold water output, even though the unit is technically working.
Tankless Water Heater Troubleshooting: What to Check First
If your tankless water heater is not working, don't panic. Here's how to start the tankless water heater troubleshooting process:
Step 1: Check for Error Codes
Most modern tankless water heaters display an error code when something goes wrong. These codes can point you directly to the issue, such as ignition failure, sensor problems, or flow rate limitations. Refer to your unit's manual or manufacturer's website to interpret the code.
Step 2: Inspect the Water Filter and Inlet Screen
Many systems have a built-in water filter and screen to trap debris. If these become clogged, water flow can be restricted, causing your tankless water heater to stop heating or shut down entirely. Cleaning these parts can restore performance.
Step 3: Examine the Flow Rate
Tankless systems require a minimum flow rate to activate. If the faucet is only slightly open or a low-flow fixture is used, it may not be enough to trigger the burner. Increasing the flow or using a different tap can confirm whether this is the issue.
When Your Tankless Water Heater Stops Working Suddenly
It's one thing if your water heater has been acting up for weeks, but it's another when your tankless water heater stops working completely. If it goes from fully functional to zero hot water, here's what to consider:
Frozen Pipes in Winter
Even in Georgia, freezing temperatures can cause exposed pipes to freeze. If incoming water can't reach the heater, you'll experience a total failure to deliver hot water.
Internal Component Failure
Heat exchangers, ignition systems, or flame sensors can fail over time, especially if maintenance is neglected. These issues often require a licensed plumber to inspect and replace parts.
Blocked Exhaust or Air Intake
Tankless systems need proper ventilation. If debris, animals, or snow block the exhaust or intake, the system may shut down as a safety measure.
Fixing Tankless Water Heater Problems: DIY vs. Professional Help
Some tankless water heater troubleshooting steps are safe to try yourself, while others require the skills and tools of a licensed plumber. Here's a quick breakdown:
You can try:
Checking power/gas supply
Cleaning the water inlet filter
Resetting the unit
Running vinegar or descaling solution through the system (if recommended by your model)
Call a plumber for:
Error codes that won't clear
Internal part replacement
Flushing heavy sediment buildup
Gas line or venting issues
At Dalmatian Plumbing, we always prioritize your safety. If you're not sure whether something is safe to tackle, it's best to let a pro handle it.
Avoiding Hot Water Problems with Your Tankless Heater
A little routine maintenance goes a long way in avoiding situations where your tankless water heater is not heating. Here's how to keep things running smoothly:
Schedule Annual Flushes
Flushing your system once a year helps prevent mineral buildup and keeps the heat exchanger efficient. This is one of the most important steps to prevent tankless water heater problems before they start.
Install a Water Softener
If you have hard water, a softener can dramatically extend the life of your tankless unit. It reduces scaling inside the system and helps maintain consistent performance.
Use Qualified Installers
Improper installation is a leading cause of performance issues. Dalmatian Plumbing ensures every installation follows code, meets manufacturer specifications, and is built for long-term reliability.
Call Dalmatian Plumbing for Tankless Water Heater Troubleshooting
If your tankless water heater is not working, let our licensed technicians take care of it. We fix tankless water heater issues the right way.
Whether it's a minor flow issue or a full system failure, our team delivers fast, honest solutions backed by experience and craftsmanship. We'll inspect your system, identify the cause, and get your hot water running again quickly and safely.
Contact Dalmatian Plumbing today to schedule a service visit or get help with tankless water heater troubleshooting. We're here to help restore comfort and convenience to your home.
