Converting from a tank to a tankless water heater in a Triangle home involves more than swapping the unit. The gas line sizing, venting, and condensate handling all change. Most of the installations that underperform for their entire lifespan were conversions where the contractor treated it as a unit swap and left the infrastructure unchanged. Drain Express scopes the full conversion before quoting it.
What Changes in a Tank-to-Tankless Conversion
Gas Line
This is almost always the most significant change. A standard residential tank water heater draws 36,000 BTU/hour. A whole-home tankless unit at full draw pulls 150,000 to 200,000 BTU/hour — roughly five times the BTU demand. The existing 3/4-inch gas supply line to the tank heater location is sized for 36,000 BTU. Running a tankless on that supply produces gas starvation under demand. In most Triangle conversions, we upsize the gas supply to 1-inch from the nearest appropriately sized supply line or from the meter. That scope is included in the estimate before work begins.
Venting
A gas tank heater uses a B-vent (double-wall metal) running vertically. A condensing tankless unit (Navien NPE, Rinnai RU) uses PVC or CPVC running horizontally through an exterior wall. The existing B-vent is typically abandoned in the wall, and a new PVC penetration is made through the nearest exterior wall. This is a cleaner installation than the old tank vent in most cases and allows more flexible unit placement.
Condensate Drain
Condensing tankless units produce acidic condensate that must drain to a floor drain, utility sink, or through a condensate neutralizer. If the new unit location does not have a nearby drain, we run the condensate line to the nearest acceptable discharge point as part of the installation.
Recirculation
A tankless without a recirculation system in a Triangle home produces longer waits for hot water at distant fixtures than the old tank heater did. We install recirculation on conversions in homes over 1,200 square feet or where the water heater is more than 30 feet from the farthest fixture. Navien and Rinnai units have built-in recirculation pump connections.
Conversion Cost
A tank-to-tankless conversion in a Durham or Chapel Hill home without existing gas line issues typically runs $2,500 to $3,200 all-in. When gas line upsizing is required, add $400 to $900 depending on run length. See Water Heater Replacement Cost for detailed breakdowns.
Is the Conversion Worth It?
For most Triangle homeowners replacing a tank heater that has reached end of life, yes — assuming the home has natural gas service. The tankless unit lasts 15 to 20 years versus 10 to 12 for a tank, reduces gas consumption 20 to 30 percent, and eliminates standby heat loss. The payback on the premium over a standard tank replacement is typically 5 to 8 years in a household running significant hot water demand. We give you the actual math for your household’s demand profile before recommending either direction.
Related Services
- Navien Installation Specifics
- Gas Tankless Installation
- Replacement Cost Reference
- Tankless Installation Overview