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
The same code number can mean something different on another series — make sure you're reading the page for your exact unit: