A tankless water heater installation done correctly lasts 15 to 20 years and cuts gas bills 20 to 30 percent compared to a standard tank. Done incorrectly — undersized gas line, wrong vent diameter, no recirculation — it delivers cold water sandwiches and error codes for its entire lifespan. Drain Express sizes the unit, the gas line, and the venting together before anything goes in the wall.
The Three Things That Determine Performance
1. Gas Line Sizing
A whole-home tankless at full draw pulls 185,000 to 200,000 BTU. Most Triangle homes have 3/4-inch supply runs sized for a 36,000 BTU tank. Running a Navien NPE-240A on an undersized line triggers gas starvation errors that look like unit failures. We calculate BTU demand and upsize the line if needed before the unit goes in.
2. Venting
Direct-vent and power-vent tankless units require specific pipe diameter, maximum run length, and termination clearances that vary by manufacturer. Vent runs correct for a tank heater are frequently wrong for a tankless. We follow manufacturer specs, not the path of least resistance.
3. Recirculation
A tankless without a recirculation pump in a home over 1,500 square feet produces long waits at distant fixtures. We install recirculation as standard on any whole-home replacement where wait times would otherwise be an issue. Current Navien and Rinnai units have built-in recirculation connections.
Installation Options
- Gas Tankless Installation — whole-home gas tankless, Navien and Rinnai primary brands, full infrastructure scope
- Navien Tankless Installation — NPE series, condensate handling, recirculation, freeze protection
- Tank-to-Tankless Conversion — full scope of what changes beyond just swapping the unit
Cost
Complete installation — unit, venting, gas line sizing and upgrade if needed, recirculation, permit, and inspection — typically runs $2,500 to $4,500 depending on unit capacity and infrastructure scope. See Water Heater Replacement Cost for a full breakdown.
Related Services
- Tankless Water Heater Repair
- Tank Water Heater Replacement
- Tankless Descaling and Maintenance
- NC Code and Permits