Rinnai tankless units need annual maintenance — more so than tank water heaters because the heat exchanger is constantly exposed to scale-forming hot water. Skipping maintenance is the most common reason warranty claims are denied.
Annual checklist
- Flush the heat exchanger — vinegar or commercial descaler, 60-90 minute job. Required annually in hard water (>11 gpg), every 2 years in soft water.
- Clean the inlet water filter — small screen at the cold-water inlet. Removes sediment before it scales.
- Clean the air inlet filter — at the base of indoor units. Lint and pet hair restrict combustion air.
- Check the venting termination — verify it's clear of leaves, insect nests, or icing buildup
- Inspect the condensate trap on condensing models — clean if any sediment
- Verify gas pressure — should be ≥4" WC inlet during fire on natural gas, ≥10" WC on propane. Pressure test annually.
- Test the pressure relief valve on the outlet line if installed (Rinnai units don't have a tank PRV but most installs include an inline one)
- Update controller firmware through the ControlR app — Rinnai pushes firmware updates that improve modulation
How often does this need to happen?
| Task | Soft water (<7 gpg) | Hard water (>11 gpg) |
|---|---|---|
| Heat exchanger flush | Every 24 months | Every 12 months |
| Inlet water filter | Annually | Twice yearly |
| Air inlet filter | Annually | Annually |
| Vent inspection | Annually | Annually |
| Gas pressure check | Every 2-3 years | Every 2-3 years |
DIY vs professional service
The flush and filter cleaning are absolutely DIY-able with a $40 pump kit from Amazon. Gas pressure testing requires a manometer and a licensed plumber. Most homeowners DIY the flush and pay a Rinnai-trained plumber every 3-5 years for a full inspection plus firmware update.
Warranty impact
Rinnai's warranty document specifies "performed annual maintenance in accordance with installation manual." If a heat exchanger fails and the inspection shows heavy scale, the claim is denied. Keep flush receipts or take photos with date.
Bottom line
One Saturday morning per year keeps a Rinnai inside warranty and at rated output for the full 15-year heat exchanger life. See our descaling walkthrough for the step-by-step.