5 Common Tankless Water Heater Issues and How to Prevent Them

Tankless water heaters are best known for their efficiency and long lifespan, but even high-quality systems can experience issues over time. Small performance changes—like fluctuating water temperature or slow heating—are often early signs that professional attention is needed. Homeowners who recognize and address these problems early can avoid costly repairs and downtime. Bell Plumbing helps residents get the most out of their tankless water heater in Redwood City, CA by sharing the most common concerns and how to handle them.

1. Mineral Buildup from Hard Water

Hard water contains calcium and magnesium that can collect inside the heat exchanger. Over time, this buildup reduces efficiency and may shorten the system’s lifespan. Flushing the unit and installing a water softener where needed can help limit this issue. Regular tankless water heater maintenance is the best way to stay ahead of scale accumulation.

2. Ignition or Flame Failure

A tankless unit relies on gas or electricity to ignite and heat water. If the system fails to ignite, it can be caused by gas supply issues, blocked vents, or a malfunctioning igniter. Scheduling professional tankless water heater repair can quickly restore reliable performance and address the underlying cause.

3. Overloaded System

When multiple hot water sources are used at the same time, the heater may struggle to keep up. This can lead to inconsistent water temperatures. Preventing this issue often involves upgrading to a larger unit or adding a second one. A licensed plumber can guide homeowners through tankless water heater replacement if the system no longer meets household demand.

4. Exhaust or Venting Problems

Proper ventilation is critical for gas-powered tankless water heaters. If vents are blocked or installed incorrectly, it can trigger error codes or shut down the system. A qualified technician should inspect and correct venting concerns during routine tankless water heater services to keep everything operating safely.

5. Cold Water Sandwich Effect

This issue occurs when a burst of cold water interrupts the hot water flow, usually at the beginning of use. While not harmful, it can be inconvenient. Installing a small recirculation system or using proper startup techniques can reduce the likelihood of this happening.

FAQs

Q: How long does a tankless water heater typically last?

A: A well-maintained tankless system can operate for 15 to 20 years, often longer than traditional water heaters.

Q: Do tankless water heaters require annual service?

A: Annual service is strongly recommended, especially in areas with hard water, to keep the system efficient and prevent breakdowns.

Q: Can pipe size affect tankless water heater performance?

A: Yes. If the gas or water lines are undersized, the heater may not function properly. Correct installation and inspection are important for safe and dependable operation.

Bell Plumbing is licensed, bonded, and insured, and we stand behind our work with a satisfaction guarantee. We have proudly served homeowners throughout San Mateo County for nearly 2 decades, providing trusted solutions for every stage of a water heater’s life. Whether it’s maintenance, repair, or replacement, our team is ready to keep your system running reliably. Call us today to schedule an appointment.