Ministerial Interpretation
The Construction Codes Act



     PROTECTION FROM BACKFLOW FOR NPC 2020
     Article 2.4.6.4.

Issue Number:      NPC 2020 - 001
Date Effective:    December 15, 2025
Expires:           The day the National Plumbing Code 2025 comes into force in Saskatchewan.
Page:              1 of 3


Purpose
To provide for clarification on how revisions and errata to the National Plumbing Code of Canada (NPC)
2020, Division B, Article 2.4.6.4. are to be interpreted while accounting for the Saskatchewan-specific
amendments within The Plumbing Code Regulations (the PC Regulations).

Discussion
As part of the adoption of the NPC 2020, Saskatchewan revised the requirements in Article 2.4.6.4. on
backflow valves with the goal of ensuring building owners had sufficient protection from sewer backups.
While the wording in NPC 2020 alluded to increased protection, it was determined that the actual
technical requirements did not provide sufficient coverage. As such, Saskatchewan amended the NPC
2020 at the time of its adoption to ensure building owners installed backflow valves in sufficient
numbers and locations to provide adequate protection from sewer backups.

With the publication of the revisions and errata in March 2025, Codes Canada reordered and
renumbered Article 2.4.6.4. of NPC 2020 to more fully explain the intent for backflow protection and to
promote greater clarity for code users. As revisions and errata are normally editorial or clerical in
nature, they are automatically adopted by Saskatchewan, as required under Clause 5(1)(b) of the PC
Regulations.

In doing so, the Saskatchewan amendments for requirements on backflow valves no longer refer to the
correct sentences in Article 2.4.6.4. of the NPC. This ministerial interpretation will correct reference
errors by aligning the Saskatchewan amendments to the NPC 2020 with the 2025 revisions and errata
published by Codes Canada. This ministerial interpretation does not change the original technical
requirements Saskatchewan adopted by amendment to the NPC 2020.
Ministerial Interpretation – NPC 2020 – 001
Protection from Backflow
Page 2 of 3

Ministerial Interpretation
NPC 2020 Division B Article 2.4.6.4. shall be interpreted with the following substituted:

         “2.4.6.4. Protection from Backflow

              1) Except as provided in Sentences (2) and (3), where a building drain or branch may be
                 subject to backflow from a fixture or a public sewer, a backwater valve shall be installed
                 on every fixture drain connected to them when the fixture is located below grade.

              2) Where more than one fixture is in the same room and all are connected to the same
                 branch, the backwater valve is permitted to be installed on the branch.

              3) A subsoil drainage pipe that drains into a sanitary drainage system that is subject to
                 surcharge shall be connected in such a manner that sewage cannot back up into the
                 subsoil drainage pipe. (See Note A-2.4.6.4. (1)).

              4) Where a building drain or branch may be subject to backflow, a backwater valve shall be
                 installed in accordance with Sentences (1), (2), (5) and (6).

              5) Except as provided in Sentence (6), a backwater valve is permitted to be installed in a
                 building drain, provided the backwater valve
                   a) does not serve more than one dwelling unit, and
                   b) has a “normally open” design conforming to
                        i) CSA B70, “Cast iron soil pipe, fittings, and means of joining,”
                       ii) CSA B181.1, “Acrylonitrile-butadiene-styrene (ABS) drain, waste, and vent pipe
                            and pipe fittings,”
                       iii) CSA B181.2, “Polyvinylchloride (PVC) and chlorinated polyvinylchloride (CPVC)
                            drain, waste, and vent pipe and pipe fittings,” or
                       iv) CSA B182.1, “Plastic drain and sewer pipe and pipe fittings,”.

              6) A backwater valve or a gate valve that would prevent the free circulation of air shall not
                 be installed in a building drain or in a building sewer.”
Ministerial Interpretation – NPC 2020 – 001
Protection from Backflow
Page 3 of 3

Authority
Section 8 of The Construction Codes Act.

Jurisdiction
This interpretation will apply throughout Saskatchewan.


Original approved and signed by:


The Honourable Eric Schmalz
Minister of Government Relations
