How to Clean the Air Filter on a Rinnai SENSEI RX
A ten-minute wash that is step two of Rinnai's own troubleshooting for a blocked air supply code — and a lot cheaper than the alternatives on that list.
A sealed-combustion heater has to pull air from somewhere, and whatever is in that air arrives at the filter first. On a SENSEI RX that filter sits behind the front panel at the top right of the cabinet, and it is washable.
It is worth knowing where it is because of what it costs you when it clogs. Restricted combustion airflow is one of the causes Rinnai lists for its blocked air supply or exhaust code — and on that code, cleaning this filter is step two. The other items on the list are vent inspection, a fan motor, and a heat exchanger.
How to do it
- Power the heater off at the controller. Press the On/Off button; the display goes blank. (The controller does not cut electrical power to the unit — it only turns the heater off.)
- Remove the front panel: two screws, then release the two latches.
- Find the filter at the upper right-hand corner of the cabinet and pull it out by the tab.
- Wash it with mild dish soap and a soft bristle brush, then rinse the soap off with clean water.
- Dry it with a lint-free towel.
- Inspect it. If it still looks dirty, wash it again. If it looks damaged, replace it rather than refitting it.
- Refit the filter and the front panel, and power the unit back on.
Rinnai is explicit that the heater must not be operated with the air filter missing, so do not leave it out to “test” anything.
How often
Inspect it periodically — realistically, whenever you are near the unit for anything else, and always as part of an annual service. How fast it loads up depends entirely on the air it is breathing: a garage next to a dryer vent or a workshop will clog one far faster than a sealed utility closet.
If yours is visibly dirty again within weeks of a wash, the filter is not the problem — where the unit is drawing air from is. That is worth raising at the next service.
Related jobs while the panel is off
Nothing else on this list requires tools:
- Check the condensate drain line is flowing freely and is not kinked or frozen where it leaves the building.
- Look at the vent terminal outside for snow, leaves, or a nest.
Those two, plus the filter, are the whole of what a homeowner can safely do about a blocked-air code — and between them they resolve a good share of them.
Source: Rinnai SENSEI RX Residential Installation and Operation Manual (100000839) (p. 66), read Aug 2026 — the manufacturer's own documentation. Procedures differ between models — always check the manual for your unit.