7.6.3.4.Size

(1) Water service pipes shall be sized according to the peak demand flow but shall not be less than NPS ¾.

     (2) Except as provided in Sentence (3), the nominal pipe size of a supply pipe that serves a fixture shall conform to
     Table 7.6.3.2.-A.

     (3) For fixtures listed in Table 7.6.3.2.-A that are permitted to have an NPS ⅜ supply pipe, a connector not more than
     750 mm long and not less than NPS ¼ may be used to supply water to the fixture.

     (4) No water system between the point of connection with the water service pipe or the water meter and the first water
     distribution pipe that supplies a water heater that serves more than one fixture shall be sized less than NPS ¾.

   (5) Except as permitted in Sentence (6), where both hot and cold water is supplied to fixtures in residential buildings
   containing one or two dwelling units or row houses with separate water service pipes, the water system may be sized in
   accordance with Table 7.6.3.4., where
   (a) the hydraulic loads for maximum separate demands on water distribution system piping are not less than 100% of
        the total hydraulic load of the fixture units given in Table 7.6.3.2.-A, 7.6.3.2.-B, 7.6.3.2.-C or 7.6.3.2.-D for private
        use,
   (b) the minimum water pressure at the entry to the building is 200 kPa, and
   (c) the total maximum length of the water system is 90 m.
   (See Note A-7.6.3.4.(5))

   (6) Where both hot and cold water is supplied to fixtures in a house containing only one dwelling unit, the water service
   pipe is permitted to be a minimum of NPS ¾ in provided,
   (a) a minimum NPS ¾ water supply piping located in the basement or lower level is extended to the base of every hot
         and cold riser that serves a maximum of one bathroom group and to the last water supply branch serving any
         basement bathroom group, fixture supply or hose bibb, and
   (b) the total hydraulic load is not more than 26 fixture units, using the values given in Table 7.6.3.2.-A.

                                                         Table 7.6.3.4.
    Water Pipe Sizing for Buildings Containing One or Two Dwelling Units or Row Houses with Separate Water Service Pipes
                                               Forming Part of Sentence 7.6.3.4.(5)

                                                                       Water Velocity m/s(1)
   Nominal Pipe Size of Water
                                               3.0                              2.4                              1.5
           Pipe, NPS
                                                                    Hydraulic Load, fixture units
               ½                                8                                7                               4
                ¾                              21                                16                               9
                1                              43                                31                              18
               1¼                              83                                57                              30

Notes to Table 7.6.3.4.:
(1) Table 2.6.3.4. is not intended to limit water velocities that are permitted by Sentence 7.6.3.5.(1).

This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.

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Code text is reproduced for reference from the Ontario Building Code (O. Reg. 163/24, 2024 Building Code Compendium). This page is provided for general information and is not an official copy. Always verify requirements against the official Ontario Building Code and confirm with your local building department.