The heat exchanger in Ruud Ultra Series Tankless is the part the 12-year warranty centers on. Same stainless construction as Rheem RTGH.
Failure modes
- Scale insulation (#1 cause): calcium scale blocks heat transfer. Overheat (Code 14) trips
- Pinhole leak after 12-15 years
- Freeze damage on outdoor units in power outages
Replacement cost
- Parts: $700-1,400 OEM
- Labor: $400-700
- Total: $1,100-2,100
Warranty
12-year heat exchanger warranty. Year-10 failure: Ruud ships part free; you pay labor.
Catch: Heavy scale at claim time = denied. Keep descaling documentation.
Bottom line
Protect through annual descaling. 12-year warranty defensible only with documented maintenance.