Tankless water heaters heat water on demand and can last a long time, but they are not maintenance free. In Texas, the biggest cause of trouble is scale from hard water, followed by gas supply, venting and sensor problems.
Common Tankless Problems
- Error codes. Codes point to ignition, venting, flow or sensor faults. Note the code before you reset the unit.
- Scale buildup. Minerals coat the heat exchanger, which cuts flow and efficiency and can trigger overheating codes.
- Lukewarm or fluctuating water. Often caused by low flow, a dirty inlet filter or scale.
- No hot water at low flow. Many units need a minimum flow rate to fire.
- Ignition failure. Can come from the gas supply, a dirty flame sensor or blocked venting.
What You Can Safely Check
Confirm power and the gas valve are on, clean the inlet water filter and check that faucets are fully open. Do not open the cabinet or work on gas or venting yourself.
Descaling
A professional descale flushes the heat exchanger with a cleaning solution. In hard water areas, many installers suggest doing it yearly. It is far cheaper than replacing the exchanger.
Repair or Replace?
If the unit is under 10 years old and the problem is scale or a sensor, repair usually makes sense. If it is old, the heat exchanger has failed, or repairs keep recurring, compare the cost against a new unit. See what affects replacement cost or our tank vs tankless comparison.
Need help in San Antonio? See tankless water heater service in San Antonio and our San Antonio page.
Frequently Asked Questions
Why is my tankless water heater not heating?
Common causes are a closed gas valve, a dirty inlet filter, scale, a venting problem or a flow rate that is too low for the unit to fire.
How often should a tankless water heater be descaled?
Often once a year, and more often in hard water areas. Follow the manufacturer guidance for your model.
Is tankless water heater repair worth it?
For a newer unit with a fixable fault, yes. For an old unit with a failed heat exchanger, replacement can be the better value.
Can I repair a tankless water heater myself?
Cleaning the inlet filter is usually fine. Gas, venting and internal parts should be handled by a licensed technician.
Need a Water Heater Pro in Texas?
Licensed local crews across Texas. Call for same-day service and a written quote before any work begins.
Call (888) 492-0093 (24/7)This guide covers safe homeowner checks only. Gas, electrical, and pressurized-plumbing repairs should be performed by licensed professionals. When in doubt, call.