A tankless water heater owner who assumes the unit needs zero attention after installation is setting themselves up for a shorter equipment lifespan and a higher chance of unexpected repair costs down the line. Unlike a traditional tank heater, tankless units have specific maintenance needs tied directly to their design.
Rinnai recommends annual descaling maintenance for its condensing tankless units, along with periodic inlet filter cleaning and visual inspection, with maintenance frequency increasing in homes with hard water. Staying on top of this simple schedule is one of the most effective things you can do to protect your investment and avoid premature failure.
Why Tankless Units Need Regular Maintenance
Tankless water heaters, including Rinnai’s RXP199iN and RX199iN, heat water on demand by running it across a heat exchanger. Mineral scale from hard water gradually builds up on this heat exchanger over time, reducing efficiency and, if left unaddressed long enough, potentially causing premature component failure.
This is fundamentally different from a tank heater’s failure mode, and it’s why manufacturers are specific about maintenance intervals for tankless units in a way they generally aren’t for tank heaters.
Annual Descaling
Descaling, sometimes called flushing, involves circulating a descaling solution (commonly a diluted vinegar solution or a commercial descaling product) through the unit’s heat exchanger to dissolve mineral buildup. Rinnai recommends this be done annually for most households, though homes with notably hard water may need it more frequently.
Inlet Filter Cleaning
Rinnai units include an inlet water filter designed to catch sediment before it enters the unit. This filter needs periodic cleaning, since a clogged filter can restrict water flow and affect performance. Check your specific model’s manual for the recommended cleaning interval, since this can vary by household water quality and usage.
Visual Inspection
Periodically inspecting venting connections, checking for any unusual noises during operation, and confirming the unit is displaying no error codes are all simple checks homeowners can do themselves between more involved professional service visits.
How Water Hardness Affects Your Schedule
Homes on hard water, generally anything above 7 grains per gallon, should expect to descale more frequently than the standard annual recommendation, since mineral buildup accelerates with harder water. Consider a water softener or scale-reduction system if you’re in a notably hard water area, since this can meaningfully extend the interval between required descaling sessions. Learn more in our guide on [water softeners and tankless water heaters].
What Happens If You Skip Maintenance
Skipping descaling doesn’t cause immediate failure, but it does progressively reduce heat exchanger efficiency, potentially trigger error codes related to reduced flow or overheating, and can shorten the unit’s overall lifespan compared to a properly maintained unit. Since these units represent a meaningful investment, a simple annual maintenance routine is a small time cost relative to the protection it provides.
Rinnai RXP199iN Condensing Tankless Water Heater with Built-In Recirculation Pump - View on Amazon
The Bottom Line
Annual descaling, periodic inlet filter cleaning, and simple visual inspection make up the core of Rinnai’s recommended tankless maintenance schedule. Homes with hard water should expect to descale more frequently, and staying consistent with this simple routine meaningfully protects your unit’s lifespan and performance.
Frequently Asked Questions
How often should I descale my Rinnai tankless water heater? Rinnai recommends annual descaling for most households, though homes with hard water may need to descale more frequently.
What happens if I never descale my tankless water heater? Skipping descaling progressively reduces heat exchanger efficiency, can trigger error codes related to reduced flow, and shortens the unit’s overall lifespan.
Can I descale my Rinnai tankless heater myself? Yes, many homeowners handle descaling themselves using a descaling pump kit and solution, following the process outlined in the unit’s manual.
Does hard water require more frequent maintenance? Yes, homes with water hardness above roughly 7 grains per gallon should expect to descale more often than the standard annual recommendation.
What is an inlet filter and why does it need cleaning? The inlet filter catches sediment before it enters the unit, and a clogged filter can restrict water flow, so periodic cleaning is recommended.
Does a water softener reduce how often I need to descale? Yes, a water softener or scale-reduction system can meaningfully extend the interval between required descaling sessions in hard water areas.
How do I know if my unit needs descaling sooner than scheduled? Reduced hot water performance, unusual noises, or specific error codes related to flow or temperature can indicate it’s time to descale sooner.
Is professional maintenance required, or can I do it myself? Basic descaling and filter cleaning can often be done by homeowners, though professional service is worth considering for more thorough annual inspections.
Does skipping maintenance void my warranty? Check your specific warranty terms, some manufacturers do require documented maintenance for full warranty coverage, so this is worth confirming directly.
What tools do I need for DIY descaling? A descaling pump kit, hoses to connect to the unit’s service valves, and a descaling solution are the basic tools needed for a DIY descaling session.
References
- Rinnai official maintenance guidance for condensing tankless units, accessed July 2026: https://www.rinnai.us
- Rinnai official product specifications for the RXP199iN, accessed July 2026: https://www.amazon.com/s?k=Rinnai+RXP199iN