Noritz Water Heater Installation Guide — Step by Step

A Noritz install is similar complexity to other tankless brands — with the addition of the Twin Pipe Adaptor (TWA) for certain venting conversions and the cascade-specific requirements for NCC commercial. This page covers both residential and commercial install requirements.

Gas line sizing (all Noritz)

Undersized gas line is the #1 install mistake. Have a plumber do a gas pressure test under full load before commissioning.

Venting

• Condensing (NRC, EZTR, EZ, NRCB, NCC): 2" or 3" Schedule 40 PVC / CPVC. Up to 100 ft equivalent length on most models. Concentric or two-pipe options
• Non-condensing (NR series): stainless Category III venting (not PVC). 4" diameter typical
• Outdoor variants (NRC-OD, NRCB-OD, NCC-OD): no venting; cabinet weather-sealed

TWA — Twin Pipe Adaptor

Noritz's TWA converts a single-pipe non-direct-vent install to a sealed-combustion two-pipe configuration. Used when:

• You need to convert an existing single-pipe vent to two-pipe sealed combustion (often required by code in airtight new construction)
• You want to add a fresh-air intake to an existing install
• Combustion air in the install space is marginal

TWA install requires a Noritz-trained installer in most cases — improper TWA install can void the warranty.

Condensate drainage

Condensing models produce 1-2 gallons/day of acidic condensate. Required setup:

• Condensate trap at unit outlet (Noritz includes)
• PVC drain line to floor drain, sink trap, or condensate pump
• Neutralizer required if running to iron drain pipe or septic
• Insulate or heat-trace drain line through unconditioned spaces

Water softener / scale filter

Required above 11 grains per gallon hardness for warranty compliance. Noritz's ecoTOUGH 316L stainless heat exchanger is more scale-tolerant than competitor exchangers — but only by 20-30%, not enough to skip the softener in genuinely hard water.

NCC Commercial cascade requirements

Cascade installs are significantly more complex than single-unit installs. Required for NCC cascade configurations (2-12 units):

• Cascade controller (Noritz-supplied) — manages rotation, modulation, and failure-isolation across the array
• Quick Connect cord daisy-chain — proprietary Noritz wiring between units. Up to 12 units
• Manifold piping — common-header gas, water inlet, water outlet, and condensate manifolds. Sizing per Noritz Cascade Installation Manual
• Isolation valves per unit — allows servicing individual units without shutting down the cascade
• Common-vent design — typically a shared concentric vent stack with proper sizing
• BMS integration (optional) — building management system integration for monitoring

Use a Noritz-trained commercial installer. Generic plumbers usually don't have cascade experience.

Electrical

Standard 120V 15A circuit per unit. Cascade installs may need dedicated circuit per unit OR a single larger circuit with appropriate breaker protection — verify per Cascade Installation Manual.

Commissioning

1. Purge air from gas line
2. Open inlet/outlet isolation valves
3. For combi (NRCB): fill hydronic loop, purge air, set pressure (12-15 psi cold)
4. Power on; verify display
5. Set temperature
6. If condensing: verify condensate drain flowing
7. For EZTR: program recirculation schedule
8. For NCC cascade: verify all units are visible in cascade controller; test rotation
9. Register warranty

Permits

Permits and inspections required in most US jurisdictions. Inspector verifies: gas line sizing, venting code compliance, condensate plumbing, isolation valves. Some commercial jurisdictions require additional plan review for cascade installs.

Bottom line

For NRC and EZTR residential: install is similar complexity to Rinnai or Navien. For NCC cascade: dramatically more complex; use a Noritz-trained commercial installer who has cascade install experience. Both warranty status and operational reliability depend on proper install.