Most tankless water heater issues come from low water flow, scale buildup, dirty filters, ignition trouble, or airflow restrictions. Start by checking power, gas supply, and filter screens. Flush the system if it has been a year or more. If the unit still will not heat or keeps shutting down, schedule professional tankless water heater service in Brentwood or Franklin, TN to protect the system and restore consistent hot water.
If you have lived in Middle Tennessee long enough, you already know how chaotic a morning can get when the shower suddenly runs cold. It usually happens on the days you are running behind or when the house is full of guests. We hear these stories every week. A tankless water heater is supposed to make life easier, not send you into a tailspin before breakfast. When it stops heating or keeps shutting off, homeowners start wondering if it is a minor issue or a sign they need water heater replacement in Brentwood or Franklin.
The truth is that most tankless problems are predictable. Once you understand how the system works, troubleshooting becomes a lot less intimidating. Let’s walk through the most common problems, the steps you can take at home, and the moments when you should call a licensed plumber who handles tankless water heater repair near you.
How Tankless Water Heaters Actually Work
A tankless system heats water only when you turn on a faucet. No big storage tank. No reheating cycle. It is a simple idea, but it means your unit relies heavily on sensors and water flow to function correctly. If anything interrupts the process, you feel it right away.
Inside the unit you will find a burner or heating element, a flow sensor, a heat exchanger, a venting system, and various temperature sensors. Most issues come down to one of those pieces getting blocked, clogged, or starved of air or gas. That is why tankless units are efficient but sensitive. A minor problem often brings the entire process to a stop.
Common Problems and How to Fix Them
Problem 1. The unit will not heat at all
This is the big one. When a tankless unit will not produce any hot water, you can usually trace it back to power, gas, or ignition.
What often causes it
- Breaker tripped
- Gas valve closed
- Dirty burner
- Ignition failure
- Blocked air intake
What you can try at home
Start at your breaker panel. A tankless unit can trip a breaker without warning. Reset it and try again. Look at the gas valve next. It should be fully open. People sometimes bump the valve while moving items around near the unit.
Give the unit a reset through the power button. Then run a hot water faucet for at least a full minute. Tankless systems need sustained flow to activate.
If it still refuses to heat, ignition or burner issues may be involved. At that point, call a professional who handles tankless water heater service in Brentwood or tankless water heater installation Franklin TN. Working with gas components is not a DIY project.
Problem 2. Water gets hot, then cold, then hot again
Temperature swings usually mean the system cannot maintain stable flow or the sensors are struggling.
Common causes
- Low water pressure
- Dirty inlet filter
- Scale buildup
- System undersized for your home
What you can do
Start with the inlet filter screen. It collects debris, and once it clogs, the unit cannot read flow correctly. Homeowners are often surprised how dirty those screens can get.
Think about your water usage too. If you run the washing machine, a shower, and a sink at the same time, an undersized unit will struggle. If your household has outgrown your equipment, it may be time to look into tankless water heater replacement cost and upgrade to a bigger system.
Problem 3. You get hot water but not nearly enough
This problem shows up a lot in homes with older units or heavy mineral buildup.
Possible reasons
- Scale inside the heat exchanger
- Weak burner flame
- Water pressure restrictions
- Low temperature setting
Try these steps
Increase the temperature by a small amount. Do not exceed 125 degrees. Check your aerators and showerheads. Mineral deposits can choke the flow at the fixture itself.
If it has been more than a year since the unit was flushed, schedule tankless water heater maintenance. Middle Tennessee water contains minerals that collect faster than people expect. A good flush can bring a tankless unit back to life.
Problem 4. The unit shuts off mid shower
This one always gets homeowners frustrated. Most of the time, it comes down to airflow, venting issues, or an overheating system.
Likely culprits
- Blocked exhaust
- Dirty air filter
- Faulty temperature sensor
- Insufficient ventilation
Steps you can take
Look at the vent outside to make sure nothing has blocked it. We have seen leaves, insulation, insects, and even small nests cause shutdowns. Clean or replace air filters if your model has them. Reduce demand and try again.
If the unit continues to shut off, stop troubleshooting and call a professional. This issue can be tied to overheating, which is something you do not want to push through. Any licensed plumber who understands tankless water heater repair Franklin TN can diagnose it safely.
Problem 5. Error codes keep appearing
Each manufacturer uses different codes, but most point to three categories. Gas issues, airflow issues, or temperature sensor problems.
Basic steps that help
- Reset the system
- Check airflow
- Confirm gas supply
- Clean filter screens
If the same code keeps coming back, do not keep resetting the unit. Repeated resets mask the problem and often lead to more expensive repairs.
How to Know When You Need a Professional
Some symptoms tell you it is time to step aside and call someone trained and licensed. This does not make you any less capable. Tankless systems have sensitive components that are easy to damage if handled incorrectly.
Call a pro if you notice
- Persistent cold water
- Repeating error codes
- Low water pressure across the entire house
- Strange noises from the burner or fan
- Scorch marks or any sign of overheating
- Gas smell near the unit
If your home is in Mt. Pleasant, Columbia, Franklin, Brentwood, or anywhere nearby, you can schedule MT Pleasant tn water heater installation or tankless service with a local team that knows these systems well.
Signs You May Need Replacement Instead of Repair
A tankless system does not last forever. Most homeowners keep them running twelve to fifteen years if maintained well, sometimes longer. But once parts start wearing out, repairs become more frequent.
Replacement is worth considering if
- The system is more than fifteen years old
- Repairs are happening every few months
- The heat exchanger has failed
- Your hot water demand has increased
- The unit cannot keep up even after maintenance
Many homeowners use this moment to switch to energy efficient water heaters TN that offer better performance and lower utility bills.
What Repairs and Replacement Usually Cost
Every home is different, so think of these as general guidelines rather than rigid prices.
Repair costs
Minor repairs like filter cleaning or recalibration are usually simple. More complex issues involving sensors, burners, or heat exchangers take more time and parts.
Replacement costs
Tankless water heater replacement cost depends on the size of the unit, venting needs, gas line upgrades, and installation conditions. Homes built before certain codes often need minor adjustments before the swap.
R and A Plumbing can handle both standard hot water heater installation and full tankless upgrades. They service Middle Tennessee daily, so they already know the local permitting requirements and installation standards.
Simple Maintenance Most Homeowners Can Do
A tankless system lasts longer when it is maintained regularly. Most of these steps are easy and safe.
Basic annual maintenance
- Flush the system
- Clean the inlet filter
- Inspect venting for blockages
- Check for small leaks
- Confirm water pressure is stable
This is the best way to avoid unexpected breakdowns and extend the lifespan of your system.
DIY Jobs vs Professional Jobs
Safe for homeowners
- Resetting the unit
- Cleaning filters
- Checking breakers
- Flushing, if you know the process well
Leave to a professional
- Gas line work
- Venting issues
- Ignition failures
- Repeating error codes
- Heat exchanger problems
- Full replacement
If you try to handle ignition or gas related repairs yourself, you could easily create a dangerous situation. A licensed plumber protects your home and ensures the system runs correctly.
Common Mistakes to Avoid
Most tankless breakdowns can be traced back to a few simple mistakes.
- Ignoring small performance issues
- Setting temperatures too high
- Blocking the vents
- Flushing the system incorrectly
- Hiring unlicensed installers
- Using parts that are not compatible with your unit
We see this often when homeowners search install tankless water heater near me and choose someone without proper licensing. It usually ends with another call for water heater repair Franklin TN or water heater installation Brentwood.
FAQs
Why does my tankless water heater run cold even when power and gas are on
It often happens when the flow sensor cannot detect enough water. Clean the inlet filter, open all valves fully, reset the unit, and test again. If it still runs cold, the ignition sequence may be failing and needs professional service.
How often should I flush my tankless unit in Middle Tennessee
Once a year is the bare minimum. Our water contains minerals that build up quickly. If you have a busy household, twice a year is even better.
Can I replace my tank water heater with a tankless system
Yes, in many cases. You may need adjustments to gas lines, venting, or electrical capacity. A licensed installer can inspect your home and tell you exactly what is needed.
If your tankless water heater is not keeping up, keeps shutting off, or needs inspection, our licensed team is ready to help. Call R and A Plumbing at (931) 982 9775 for fast tankless water heater service in Brentwood, Franklin, Mt. Pleasant, and surrounding Middle Tennessee communities. We will diagnose the issue, explain your options clearly, and fix the problem the right way.