Rinnai Tankless Humming Noise: Normal or Not?
On this page (6 sections)
The Short Answer: A steady hum or whoosh while hot water runs is the combustion fan and is normal. A hum when nobody is using water is usually a recirculation pump on models that have one. Noises worth a service call are a fan that grinds, rattles, or surges, a hum that comes with an error code, and any noise together with a gas smell.
Match the sound to when it happens
| When you hear it | Most likely source | What to do |
|---|---|---|
| Only while hot water runs, smooth and steady | Combustion fan changing speed with the burner | Nothing; this is normal operation |
| Briefly after the tap closes | Fan clearing the combustion chamber | Normal |
| On a schedule, or all day, with no water in use | Recirculation pump (RUR, RSC, or an external pump) | Check the recirculation setting |
| Grinding, scraping, or a rising whine over weeks | Fan bearing wear or debris near the fan | Service visit before it fails |
| Hum or rattle followed by code 10 or 61 | Fan or airflow problem | Note the code; service |
| Rushing or whistling at the pipes | A partly closed valve or high water pressure | Check valves; see below |
Recirculation pump noise
On models with a built-in pump, the pump can run on a timer, a learned schedule, or continuously, depending on how it was set up. If the hum bothers you, or the heater seems to run constantly, check the recirculation mode in your controller or app. A pump that has become noticeably louder or hotter than before may be wearing out.
Fan noise worth attention
The combustion fan moves air for every burner cycle, so it gets a lot of use. Wear usually announces itself as a rougher sound, a squeal at start-up, or speed that hunts up and down. Rinnai lists code 61 as a combustion fan fault and code 10 as an air or exhaust blockage that can involve fan debris. A technician checks that the fan wheel spins freely, inspects the wiring, and replaces the fan motor if needed; that is a part repair, not a reason to replace the heater.
On outdoor units, leaves or nesting material near the intake can make the fan sound different. Look from outside and clear what you can safely reach.
Pipe and valve noise
A whistle or rush from the pipes rather than the cabinet usually comes from a service valve that is not fully open or from high household water pressure. Make sure the valves under the heater are fully open. If the whole house has noisy pipes, a plumber can check the incoming pressure and the pressure-reducing valve.
When to turn it off
Turn the heater off at its controller and call for service if the noise comes with a burning or gas smell, a loud bang at ignition, visible smoke, or water coming from the cabinet. If you smell gas, leave the building and call the gas utility from outside.
Related: tankless clicking noises, tankless banging noise, and Rinnai code 10.
Frequently Asked Questions
Q: Can scale make a Rinnai noisy? A: Scale tends to cause a rumbling or kettle-like sound and overheating codes rather than a hum. If you hear that along with lukewarm water or LC codes, a flush is the likely fix.
Q: My Rinnai hums even with the power off. Is it the heater? A: No. With power off, the fan, pump, and controls cannot run. Look for another source nearby, such as a transformer, a refrigerator, or plumbing noise from elsewhere in the house.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- Rinnai: official document library (opens in a new tab)Select your exact model and owner manual before interpreting a fault or reset procedure.
- PG&E: recognizing and responding to a gas leak (opens in a new tab)Emergency actions for suspected fuel-gas leaks.
Editorial standards and corrections · Prepare a useful service request