Flush ProsA tankless unit is typically a $3,000–$6,000 installed investment, and the warranty is a real part of its value. But the coverage isn't one number — it's three (heat exchanger, parts, labor), and each brand attaches conditions. Here's how the five brands we service compare, pulled from their current residential warranty documents.
The numbers
| Brand | Heat exchanger | Parts | Labor | Worth knowing |
|---|---|---|---|---|
| Navien (NPE-A) | 15 years | 5 years | 1 year | Drops to 5 years on uncontrolled recirculation. Buying online voids the warranty. |
| Rinnai (Sensei condensing) | 15 years or 12,000 hours | 5 years | 1 year — 5 if registered within 90 days | Non-condensing series are typically shorter — check your model. Excludes "improper maintenance (such as scale build-up)." |
| Noritz | 12 years standard; 25 years on EZ series | 5 years | 1 year | 25-year models: EZ71, EZ98, EZ111, EZTR50, EZTR75 (or 15,000 burn hours). |
| Rheem (RTGH) | 15 years | 5 years | 1 year | All coverage ends at 12,000 operating hours. Explicitly excludes "lime, mineral build-up, or scale." |
| Bosch (Greentherm) | 15 years | 5 years | — | Register after install to activate coverage. |
Check your own paperwork — terms change by model year and by whether the unit is in recirculation. But the pattern is consistent: long heat-exchanger coverage, short labor coverage, and registration matters.
The clause that matters most
Every one of these warranties excludes failures caused by scale or lack of maintenance. Rheem says it outright; Rinnai calls it "improper maintenance"; Navien requires "regular maintenance." In practice, when a heat exchanger fails in year 8, the manufacturer's first question is: can you show it was descaled annually?
That's the whole reason we keep a service record for every unit we flush. A dated record from a Noritz PROCard-verified service company is exactly what a claim needs.
Register the unit
Rinnai's labor coverage goes from 1 year to 5 just for registering within 90 days. Bosch requires registration. It takes five minutes on the manufacturer's site with the serial number — if you're not sure whether your installer did it, we'll check the plate during your flush and tell you.
If you're still choosing a unit
The warranty is one input. The others we'd weigh, in order:
- Size it to your peak demand, not your square footage. Two showers plus a dishwasher at 6 pm in January (with 50°F incoming water) typically needs a 199,000 BTU unit. Undersized units run at full tilt and scale faster.
- Condensing vs. non-condensing. Condensing units cost more up front and save on gas; they also need a condensate drain.
- Serviceability. Isolation valves and a flush kit installed on day one turn the annual flush into an hour instead of a project. If your installer skipped them, it's worth having a plumber add them before the first flush.
- Water treatment. On Utah water, a softener upstream is the single biggest thing you can do for the unit's lifespan — more than brand choice.
Ready for your annual flush?
$225 flat · about an hour · warranty record kept on file. Softener, filter or RO? Ask for a quote when you book.