Inconvenient, rarely dangerous
Unlike a failing tank, a tankless unit holds very little water, so a breakdown seldom puts much water on the floor. The usual complaint is cold water at the tap, hot water that cuts in and out, or an error code on the front panel. That means most tankless problems can wait for a daytime appointment.
The exceptions are a gas smell, water actively leaking from the unit, or scorching or burning odors. A gas smell means leaving the house and calling 911 or SoCalGas from outside. A leak means closing the water supply valves under the unit.
Safe checks before you call
- Is the display on? If not, check the breaker or plug that powers the unit; even gas tankless heaters need electricity.
- Is there an error code? Note it exactly and look it up in the owner's manual.
- Is gas reaching other appliances, such as the stove? If nothing gas works, the issue may be at the meter.
- Are the water valves under the unit fully open?
- Is the problem only at high demand, such as two showers at once? That can be a flow limit rather than a fault.
- Has the unit ever been descaled? Hard water scale is a common cause of tankless trouble.
Symptoms and likely causes
| Symptom | Possible cause |
|---|---|
| No display, no heat | Tripped breaker, unplugged unit, failed power supply |
| Error code and shutdown | Ignition, flame, venting or overheating fault; see the manual |
| Hot then cold bursts | Low flow, scale buildup, or a clogged inlet filter |
| Hot water fades during showers | Demand above what the unit can heat, or scale |
| Water dripping from the unit | Leaking fitting or heat exchanger; close the supply valves |
Call now, or book a visit?
- IfYou smell gasLeave and call 911 or SoCalGas from outside. Do not reset the unit.
- IfWater is leaking from the unitClose the cold and hot service valves under it and turn off power. Call a plumber.
- IfError code with no leak and no gas smellNote the code and book a daytime visit. Resetting repeatedly can mask the problem.
- IfHot water is weak but workingSchedule service and ask about descaling.
Questions to ask
- What does this error code mean on my model?
- Is the heat exchanger scaled, and should it be flushed?
- Are the service valves and inlet filter in working order?
- Is my gas line and venting sized correctly for this unit?
- What is your CSLB license number?
Common questions
- Is a tankless heater outage an emergency?
- Usually not. Without a gas smell or an active leak, it can normally wait for a daytime service visit.
- Why does my tankless heater need electricity if it runs on gas?
- Its controls, ignition and fan run on power. A tripped breaker can stop the unit even with gas available.
- How often should a tankless heater be flushed?
- Follow the manufacturer's manual. Hard water can mean more frequent flushing than in soft water areas.
General information for Brea, not a quote or professional advice. In an emergency, call 911.