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.
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: