Stiebel Eltron maintenance is simpler than combi-boiler maintenance — no combustion analysis, no condensate trap on most units, no anode rod on stainless. But there are critical tasks that determine long-term reliability.
Tempra Plus annual maintenance
- Clean inlet filter — the most-neglected maintenance task and the cause of most performance complaints. Pull strainer at cold inlet; rinse; reinstall
- Descale in hard water — flush with vinegar or descaler. Annual in >10 gpg water; every 2 years in 5-10 gpg; every 3+ years below 5 gpg
- Visual inspection — fittings, mounting, electrical connections
- Display fault history — review for intermittent codes that didn\'t lock out
- Verify breaker tightness — high-amperage connections loosen from thermal cycling
Descaling Tempra Plus
- Power off at all breakers; verify with voltage tester
- Close inlet and outlet shutoffs
- Connect descaling pump to service tees (Stiebel-compatible isolation kit recommended)
- Circulate vinegar OR commercial descaler (CLR / Rydlyme) for 30-60 minutes
- Flush with fresh water until pH neutral
- Open shutoffs; restore power; verify operation
Hard-water installs without descaling lose flow capacity progressively. Scale insulates the heating element, raising power draw and shortening element life. Descaling is the single best longevity action on Tempra Plus.
DHC and Mini point-of-use
- Annual inlet filter clean — same as Tempra; smaller filter
- Descale every 2-3 years in hard water; less frequent in soft water
- Verify mounting and water connections at annual flush
- No regular electrical maintenance — connections are sealed
SHC mini-tank
- Annual flush — drain via the drain valve to remove sediment
- T&P test annually — lift the lever, verify discharge stops
- ECO reset verification — confirm reset button function (don\'t actually reset unless tripped)
- Anode rod inspection at year 4-5 (SHC has standard magnesium anode like full-size tanks)
Accelera 300 E heat pump
- Monthly: vacuum the air filter (washable); inspect condensate drain
- Quarterly: wipe condensate pan
- Annually: coil cleaning with foaming HVAC coil cleaner; mode review; verify ambient conditions still meet 45-95°F requirement
- Every 4-5 years: anode rod inspection (Accelera has standard anode); replace if > 50% consumed
- Every 2-3 years: tank flush to remove sediment
Hard water management
Hard water is the #1 enemy of Stiebel Eltron electric tankless. The heating elements scale rapidly in hard water; the heat exchanger develops mineral deposits that insulate.
| Hardness | Recommendation |
|---|---|
| 0-5 gpg (soft) | Descale every 3-4 years; no softener required |
| 5-10 gpg (moderate) | Descale every 2 years; softener optional but beneficial |
| 10-15 gpg (hard) | Annual descaling OR install whole-home water softener |
| 15+ gpg (very hard) | Water softener not optional. Without one, heating element life drops to 3-5 years |
Bottom line
Inlet filter monthly visual; annual cleaning. Descale based on water hardness. Element resistance test every few years. Accelera adds monthly filter cleaning. Hard-water homes without softeners must descale annually or accept reduced lifespan.