Noritz NR981 Vent Installation

by JP

Can I install the Noritz NR981 tankless water heater in the basement and run the venting and air pipe 40 ft. with several direction changes. What is the recommended pipe type?


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Sep 29, 2013
Noritz venting guideline
by: Mike

Hi JP,
every manufacturer of tankless water heaters, including Noritz, emphasize the importance of using the vent pipe specified by the company who produces the heater.

Noritz NR981, as an indoor water heater, has to use the vent pipe made of materials that are specified for this appliance. This model uses 4" Category III or 5"/3" stainless steel pipe, both concentric direct vent type.

If you haven't read the manual, this is what Noritz recommends:

- First of all, this indoor unit must be installed inside only with the correctly done installation of the venting system, so it gets enough air supply for gas combustion and correctly transfer the products of combustion out.

- There should not be any obstacles around the vent terminal, also the termination should not be closed or blocked anytime.

- The exhaust must not blow on the elements which are not heat-resistant, including windows, walls, porch, deck, balcony doors, trees, bushes, flowers...

- There should be enough clearances and according to the national codes. For example: 24" clearance or more in front of the flue terminal, 3" above or below the vent pipe, for service.

- The maximum vent length is 41 ft with the zero elbows. If for example 3 elbows are used, maximum vent length is 24 ft. With every change of the maximum length the dip switch has to be adjusted. If the maximum vent length is exceeded the result is improper gas combustion.

- The vent pipe must slope downward 1/4" for every 12" in length.

- The vent pipe has to maintain its diameter all the way.

- White smoke from the exhaust vent during the cold weather is normal.

- Keep also in mind that the local or national codes has to be met.

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