Rinnai SENSEI Code SS
Service soon reminder. A time-based service reminder, not a fault. When the installer enables it, the SENSEI counts down from the interval chosen at setup — six months, one year, or two years — then displays SS to say the heat exchanger should be flushed. On this generation it is the *only* scale warning you get: the SENSEI has no LC lockout.
DIY fixThe verdict
Descale the unit
Book or do a descale. Nothing has failed yet. A DIY flush costs about $25-40 in white vinegar if the isolation valves are fitted; a plumber's flush is typically $150-300. On a SENSEI, ignoring it does not lead to a scale lockout — it leads straight to codes 14 and 54.
Typical cost: $25–$300
US estimate for parts and labor. Prices vary by region and by who does the work — see how we estimate costs.
What the manual says
The meaning above is transcribed from the manufacturer's diagnostic documentation for the SENSEI — not averaged across the brand.
Source: Rinnai Troubleshooting Tankless Water Heater Diagnostic Codes (100000652) (p. 66), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
- Flush the heat exchanger — see our descaling guide.
- To clear SS on a SENSEI, push the On/Off button on the temperature controller five times within five seconds.
- If your water is hard, ask about treatment: above roughly 12 grains per gallon Rinnai considers a softener or conditioner a requirement.
Frequently asked questions
How is SS reset on a SENSEI?
Push the On/Off button on the controller five times within five seconds. The SENSEI RX is different — there you hold the A button on the PC board until SS disappears.
My unit never shows SS.
Then the reminder was left disabled at installation — parameter 03 set to 'not active'. On a SENSEI that means no scale warning at all, so flush on a schedule: once a year for most water, twice a year on hard water.
Why does my SENSEI not have an LC code?
Rinnai only lists LC and LC0-LC9 for the SENSEI RX/CX series and the older non-SENSEI units. The SENSEI generation sits in between and has no scale lockout — which makes the SS reminder, and a flushing schedule, matter more here than on either neighbour.
Code SS on other Rinnai series
Other Rinnai series report code SS under the same fault name, but each manual is transcribed separately and they do not read alike: