A Rheem tankless water heater is a significant investment — one that should deliver reliable hot water for 15 to 20 years or more with proper care. The difference between a unit that hits that mark and one that fails early almost always comes down to maintenance. Mineral scale builds up on the heat exchanger, inlet filters clog, vent terminations get blocked, and what started as a high-performing condensing unit quietly loses efficiency and reliability. This guide covers every maintenance task Rheem recommends for their IKONIC and RTG Series tankless units, how often to do it, and the warning signs that tell you something needs attention now.
PlumbersCrib.com is an authorized Rheem dealer. Browse the full Rheem tankless lineup at PlumbersCrib.com or contact our team with any technical questions.
Why regular maintenance matters
The performance, safety, efficiency, and longevity of your Rheem tankless unit depends heavily on proper upkeep. Skipping maintenance can increase the risk of breakdowns, energy waste, and premature replacement. Mineral deposits form inside the heat exchanger, restricting water flow and forcing the unit to work harder — reducing efficiency and increasing wear over time.
Most maintenance needs also vary by product and water conditions. Your plumber is the best resource for knowing what is right for your specific Rheem unit. Always refer to the Use and Care Manual for your model for the manufacturer's specific guidance.
General rule: Annual maintenance minimum for all Rheem tankless installations. Every six months in hard water areas. Spring or fall are ideal timing — moderate usage periods with stable temperatures make it easier to take the unit offline briefly for service.
Rheem's recommended annual maintenance checklist
Rheem recommends these five key maintenance tasks be performed at least once a year, typically by a licensed plumber, to keep your unit in top shape.
1. Clean the water filter
The small inlet filter on the cold water supply connection prevents debris from entering the heat exchanger. Remove it, rinse it under running water, and reinstall. A clogged inlet filter reduces flow rate, triggers low-flow error codes, and puts unnecessary strain on the unit. On high-sediment water supplies, check it every three months rather than annually. This is one of the simpler tasks that most homeowners can handle themselves with basic tools.
2. Flush the heat exchanger
This is the most important maintenance task for any Rheem tankless unit. Mineral scale accumulates inside the heat exchanger over time, reducing heating efficiency and increasing wear. Rheem recommends a descaling solution flush — typically food-grade white vinegar or a commercially formulated descaler — circulated through the heat exchanger to dissolve deposits before they harden. The flush interval will vary based on water conditions — annually in moderate water areas, every six months in hard water areas above 7 grains per gallon hardness.
The Rheem IKONIC's dual stainless steel heat exchangers are more resistant to scale than the single copper heat exchanger in the RTG Series — but both require descaling on a regular schedule. This task involves isolating the unit, connecting a pump to the service ports, and is best handled by a licensed plumber rather than a homeowner.
3. Burner inspection
A licensed technician should inspect the burner assembly annually for soot buildup, proper ignition, and any signs of corrosion or wear on the igniter and flame sensor. A dirty or degraded flame sensor can cause ignition failures and nuisance shutdowns. Soot buildup on the burner indicates incomplete combustion — which reduces efficiency and can indicate a venting or gas pressure problem. Tasks involving burners or gas components should always be left to a licensed professional.
4. Temperature and pressure valve inspection
The temperature and pressure relief valve is a safety device that releases excess pressure if the system overheats or over-pressurizes. Lift the valve handle briefly to confirm water flows freely through the discharge pipe. If it does not release or continues to leak after testing, replace it immediately. A failed pressure relief valve is a safety hazard — not a maintenance item to defer. Rheem recommends this inspection at every annual maintenance visit.
5. Condensate neutralizer inspection — IKONIC and condensing models only
The Rheem IKONIC is a condensing unit that produces acidic condensate as a byproduct of the secondary heat exchanger. A condensate neutralizer — a small cartridge filled with limestone media — raises the pH of the condensate before it drains. Rheem notes a minimum 10-year life expectancy on the condensate neutralizer, but it should be inspected at every annual maintenance visit. Check the housing, confirm the drain line is clear and flowing, and replace the media if it is saturated or depleted. The non-condensing RTG Series does not produce condensate and does not require a neutralizer.
Additional maintenance items to check annually
Beyond Rheem's core five-item checklist, a thorough annual maintenance visit should also include:
Inspect and clear vent terminations. Walk to the exterior vent termination and confirm both the exhaust and intake are clear of obstruction — bird nests, insect nests, leaves, debris, ice, and snow are all common blockers. A blocked exhaust vent can cause carbon monoxide to back-draft. A blocked intake causes combustion air starvation and nuisance shutdowns. Check after any major weather event.
Confirm gas pressure. Inadequate gas inlet pressure is one of the most common causes of poor performance on Rheem tankless units — and one of the most commonly overlooked. If the unit has always seemed to underperform relative to its rated GPM output, gas pressure is often the culprit. A licensed technician should confirm inlet pressure is within Rheem's specified range.
Review EcoNet error code history. On Rheem IKONIC models with built-in EcoNet Wi-Fi, the app stores a history of error codes. Recurring codes that the unit has been self-clearing tell you where the next failure is likely to develop. Reviewing the error history at every maintenance visit is particularly easy on Wi-Fi-connected IKONIC models where the log is accessible from the app without touching the unit.
Annual maintenance checklist at a glance
| Task | Applies to | Frequency | Who performs it |
|---|---|---|---|
| Clean inlet water filter | IKONIC and RTG Series | Annually — every 3 months on high sediment water | Homeowner or technician |
| Flush heat exchanger | IKONIC and RTG Series | Annually — every 6 months in hard water areas | Licensed technician |
| Burner inspection | IKONIC and RTG Series | Annually | Licensed technician |
| Temperature and pressure valve inspection | IKONIC and RTG Series | Annually | Licensed technician |
| Condensate neutralizer inspection | IKONIC only | Annually — minimum 10-year life expectancy | Licensed technician |
| Vent termination inspection | IKONIC and RTG Series | Annually — after major weather events | Homeowner or technician |
| Gas pressure confirmation | IKONIC and RTG Series | Annually | Licensed technician |
| EcoNet error code history review | IKONIC Wi-Fi models | Annually | Technician or homeowner via app |
Warning signs that need attention now
Do not wait for the annual maintenance visit if any of these symptoms appear on your Rheem unit:
Reduced hot water output or slower heating. If the IKONIC or RTG is struggling to deliver consistent hot water, scale buildup on the heat exchanger is the most likely cause — restricting heat transfer and water flow.
Fluctuating water temperature. Sudden shifts between hot and cold during a session typically indicate mineral buildup in the heat exchanger, a faulty thermostat, or flow sensor issues.
Error codes on the display or EcoNet app. Rheem IKONIC units display diagnostic codes when a component is underperforming. Do not clear and ignore recurring codes — diagnose the root cause. A pattern of the same error code returning is the unit telling you what is about to fail. EcoNet Wi-Fi models make this particularly easy — the error history is accessible in the app without touching the unit.
Unusual sounds. Popping, banging, or whistling during operation can indicate scale buildup, burner issues, or flow restrictions.
Visible leaks or moisture. Any water around the unit — at fittings, the condensate drain, or the pressure relief valve discharge — needs immediate investigation.
Spike in energy bills without change in usage. A sudden increase in gas consumption with no change in household demand is a reliable indicator of declining heat exchanger efficiency — almost always scale-related.
How water quality affects your maintenance schedule
Hard water — above 7 grains per gallon — requires heat exchanger descaling every six months rather than annually. In very hard water areas, a water softener upstream of the unit is strongly recommended. The Rheem IKONIC's dual stainless steel heat exchangers handle hard water better than the RTG's copper heat exchanger over the long term — but both require a regular descaling program in hard water conditions.
High sediment content means the inlet filter needs cleaning every three months rather than annually. Visible debris in the filter at the annual service visit is a clear signal to increase frequency.
Cold inlet water in northern climates means the unit works harder through winter — justifying more frequent inspection intervals in the spring after peak seasonal demand.
Frequently asked questions
How often should I flush my Rheem tankless water heater?
Rheem recommends at least annually, with flush intervals varying based on water conditions. In hard water areas above 7 grains per gallon, every six months. Always refer to the Use and Care Manual for your specific model.
What is the ideal temperature setting?
Rheem recommends 120°F to 125°F for most residential applications — a good balance of comfort, scalding prevention, and energy efficiency. All Rheem IKONIC and RTG units ship with a factory default of 120°F.
Will skipping maintenance affect my Rheem warranty?
Possibly — Rheem's warranty terms require proper maintenance and may exclude damage caused by scale buildup without a documented maintenance record. Check your specific warranty documentation and Use and Care Manual for details. Some tasks must be performed by a licensed technician to maintain warranty coverage.
When is the best time to schedule Rheem tankless maintenance?
Spring or fall. Spring is ideal for northern climates — after peak winter usage when the unit worked hardest. Fall is ideal for southern climates — before the cooler months increase demand.
Does the Rheem RTG non-condensing unit need a condensate neutralizer?
No — the RTG Series is non-condensing and does not produce condensate. A condensate neutralizer is only required on condensing units like the Rheem IKONIC Series.
Can I build a relationship with a plumber for ongoing Rheem maintenance?
Yes — and Rheem specifically recommends it. Having a licensed plumber who knows your specific unit, its service history, and your local water conditions is one of the best ways to maximize the life of your Rheem tankless. They will also be on call when you need them for something else down the road.
Shop Rheem tankless at PlumbersCrib.com
- Rheem IKONIC Series — 0.96 UEF condensing, dual stainless steel heat exchangers, 8.4 to 11.2 GPM
- Rheem RTG Series — 0.82 UEF non-condensing, copper heat exchanger, 7.0 to 9.5 GPM
Contact our team or call 877-881-5501 Monday through Friday with any product or technical questions.