top of page

ASME B31.9 (Building Services Piping)

ASME B31.9


ASME B31.9 applies to the following building services:

  • Water for heating and cooling

  • Condensing water

  • Steam or other condensate

  • Steam

  • Vacuum

  • Compressed air and other nontoxic and nonflammable gases

The requirements of this code also apply to boiler external piping for steam boilers with 15 psig (103.5 kPa) maximum pressure and for water heating units having 160 psig (1104 kPa) maximum pressure and 250°F (121°C) maximum temperatures. It is noted that the boiler external piping exceeding the above limits of pressure and temperature fall within the scope of ASME B31.1 and ASME Section I.

This code places size and thickness limitations on the piping made of different materials. The requirements of this code shall apply to the piping of up to and including those sizes and thicknesses. These limitations are as follows:

  • Carbon steel: NPS 30 (DN 750) in O.D. and 0.500 in (12.7 mm) wall

  • Stainless steel: NPS 12 (DN 300) and 0.500 in (12.7 mm) wall

  • Aluminum: NPS 12 (DN 300)

  • Brass and copper: NPS 12 (DN 300) (12.125 in or 308 mm O.D. for copper tubing)

  • Thermoplastics: NPS 14 (DN 350)

  • Ductile iron: NPS 18 (DN 450)

  • Reinforced thermosetting resin: NPS 14 (DN 350)

Piping made of other materials permitted by this code may also be used for building services.

The piping within the working pressure or temperature limits shown in Table A4.1 shall be designed and constructed in compliance with the requirements of ASME B31.9.

ASME B31.9 does not cover requirements for economizers, heaters, pumps, tanks, heat exchangers, and other equipment within the scope of ASME Boiler and Pressure Vessel Code.

Effective Code Edition, Addenda, and Code Cases

For any specific application, the effective edition, addenda, and code cases of ASME B31.9 shall be determined in accordance with the approach followed for ASME B31.1.

Working Pressure and Temperature Limits of ASME B31.9

Piping Engineering Services Company


Located in Calgary, AlbertaVancouver, BCToronto, OntarioEdmonton, AlbertaHouston TexasTorrance, CaliforniaEl Segundo, CAManhattan Beach, CA; Concord, CA; We offer our engineering consultancy services across Canada and United States. Meena Rezkallah.

bottom of page