Tankless Water Heater Repair in San Jose

Residential & Commercial Repair for All Makes & Models

When your tankless water heater stops working, the disruption is immediate. Cold showers, halted laundry, a kitchen that won’t cooperate. We’ve been helping San Jose homeowners and businesses with hot water issues since 2006, and our team carries over 40 years of combined plumbing experience. As a family-owned company founded by Cory and Jeremy Southerland, we approach every repair with the full-service plumbing knowledge that water-heater-only services can’t match.

We repair tankless water heaters for both residential and commercial customers throughout San Jose, and emergency service is available 24 hours a day, 365 days a year.

Don’t wait out a cold morning. Call our tankless water heater repair plumbers in San Jose at (408) 669-4222 or contact us online for a free estimate.

Why San Jose Homeowners Call CMS Plumbing

We offer free, detailed estimates before any work begins, and we don’t perform work you haven’t authorized. Our 4.8-star Google rating reflects that commitment. Every technician is trained through our in-house program to our own standards, not just a manufacturer’s checklist.

Our credentials go deeper than a plumbing license. We hold a PG&E Certified Dig Safely OQ Card Contractor credential and a Backflow Testing Certification, which means we understand the gas line, venting, and broader system factors that often cause a tankless unit to fail in the first place. When we finish, we restore the work area to its original condition and haul away any replaced components or old units at no additional charge.

Signs Your Tankless Water Heater Needs Repair

Not sure if what you’re experiencing warrants a service call? These are the most common warning signs we hear from San Jose customers:

• No hot water, or water that won’t heat past a certain temperature
• Inconsistent or fluctuating water temperature mid-shower
• Error codes showing on the unit’s control panel
• Popping, rumbling, or banging noises when the unit fires
• A sudden rise in your gas or energy bills with no change in usage
• Discolored water or an unusual odor from the hot tap
• Unit powers on but delivers cold water only

Any one of these can point to a specific failure. The sooner it’s diagnosed, the less likely a manageable repair turns into a full replacement.

Common Tankless Water Heater Problems We Repair

We repair tankless water heaters of all makes and models, and our full-service plumbing background means we diagnose the whole system, not just the unit itself. Incoming cold water temperature, unit location, gas line sizing, and flue configuration all factor into how a tankless system performs.

Mineral Scale on the Heat Exchanger
Hard water deposits calcium and magnesium on the heat exchanger over time. In San Jose’s water environment, this is one of the most common causes of reduced output, rising energy costs, and error codes. Descaling can help restore efficiency and protect the component.

Venting & Flue Pipe Issues
Blocked, damaged, or improperly sized vent pipes prevent combustion and cause the unit to shut down. Diagnosing this correctly requires a plumber familiar with venting requirements, not just the heater itself.

Ignition & Burner Failures
When the burner won’t fire, you get cold water regardless of the thermostat setting. Ignition problems can stem from the igniter, the gas valve, or the control board.

Flow Sensor Malfunctions
The flow sensor tells the unit a tap has been opened and triggers heating. A faulty sensor means the unit may not activate.

Gas Supply Issues
Insufficient gas line pressure or an undersized supply line restricts heater output. We assess gas line sizing as part of every gas tankless diagnosis.

Demand Overload
Running too many hot water fixtures simultaneously can trigger shutdowns and accelerate component wear over time.

San Jose’s Hard Water & Your Tankless Unit

San Jose Water’s 2024 Consumer Confidence Report places system-average water hardness at approximately 190.5 mg/L, classified as very hard. Water drawn from local groundwater wells in the Santa Clara Valley tends to carry higher mineral concentrations, and hardness can vary by neighborhood depending on the mix of groundwater and imported surface water reaching your area.

That mineral load continuously deposits on the tankless heat exchanger, reducing efficiency and accelerating wear. In this environment, most units need descaling every one to two years. Without it, scale accumulation can shorten the unit’s lifespan, drive up energy bills, and eventually contribute to component failure. If your unit has never been descaled, that history may be part of what’s driving a current repair need.

What to Expect When We Arrive

Our technician inspects the unit, identifies the specific failure point, and walks you through all available repair options before any work begins. We provide a free, detailed estimate upfront. You decide what gets done. If the unit’s age or condition makes repair a poor investment relative to replacement, we can say so clearly and let you make an informed decision. Once work is authorized and completed, we restore the work area and remove any old components or units at no charge.

Tankless Water Heater Brands We Service

We repair tankless water heaters from all major manufacturers. Our team is familiar with Rinnai, Navien, Noritz, Bradford White, Rheem, A.O. Smith, and State Water Heaters, among others. Each brand uses a different error code system and component architecture, and our technicians work across multiple platforms rather than a single product line.

Schedule Tankless Water Heater Repair in San Jose

Hot water doesn’t operate on a schedule, and neither do we. Emergency service is available 24 hours a day, 365 days a year, with free estimates on every job. Whether you’re a homeowner dealing with a sudden failure or a property manager with a commercial unit down, we’re ready to help throughout San Jose and the surrounding Bay Area.

Call CMS Plumbing at (408) 669-4222 or contact us online to schedule your repair. We can diagnose the problem, give you a clear estimate, and help restore your hot water service.