Rinnai SENSEI RX Code SS
Service soon reminder. A time-based service reminder rather than a fault. When the installer enables it, the SENSEI RX counts down from the interval chosen at setup — six months, one year, or two years — and then displays SS to say the heat exchanger should be flushed. Rinnai is direct about the stakes: flushing prevents damage, and hard water must be treated to prevent scale build-up or damage to the heat exchanger.
DIY fixThe verdict
Descale the unit
Book or do a descale. Nothing has failed yet — this is the reminder that arrives before the LC lockout does. A DIY flush costs about $25-40 in white vinegar if the isolation valves are already fitted; a plumber's flush is typically $150-300. Ignoring it is how units end up with 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 RX — 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 for the SENSEI RX procedure, including the dES mode Rinnai's manual uses.
- To clear SS on a SENSEI RX, press and hold the A button on the PC board until SS disappears.
- 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
Is SS telling me something is broken?
No. It is a timer the installer set — six months, one year, or two years — telling you the heat exchanger is due a flush. The fault code that means scale has actually built up is LC.
How is SS reset on a SENSEI RX?
Press and hold the A button on the PC board until SS disappears. Note that the reset is different on the older SENSEI generation, where it is five presses of the On/Off button within five seconds.
My unit never shows SS. Is that a problem?
It means the reminder was left disabled at installation (parameter 03 set to 'not active'). Flush on a schedule anyway: once a year for most water, twice a year on hard water.