Last updated
Values this chapter turns on
- static pressure that calls for a reducing valve
- 550 kPa
- static pressure that calls for a reducing valve
- min air gap, or twice the outlet diameter if more
- 25 mm
- min air gap, or twice the outlet diameter if more
- hot water run that needs recirculation or tracing
- 30 m
- hot water run that needs recirculation or tracing
- max water closet flush in a Group C building
- 4.8 LPF
- max water closet flush in a Group C building
Section 7.6. covers the water side of the plumbing system: how piping is arranged and valved, how it is protected from backflow, how it is sized, and how fixtures save water. The House exam stops at one or two dwelling units. The All Buildings exam adds what matters in apartments, offices, schools and restaurants: risers, public washrooms, flush valves, fire sprinkler connections and premise isolation.
Arrangement of piping and valves
Valve rules are the most common lookup questions in this section. The table below sorts them by building type (OBC Div. B 7.6.1.3.OBC Div. B 7.6.1.3. Control and Shut-Off Valves(1) A building control valve shall be provided (a) on every water service pipe at the location where the water service pipe enters the building, or (b) on the water distribution system at a location immediately downstream of the point of entry treatment unit, where the building is served by a point of entry treatment…).
| Where | What is required |
|---|---|
| Every water service pipe, where it enters the building | A building control valve (or just downstream of an in-building point of entry treatment unit) |
| Just downstream of the building control valve (or meter) | A drain port; for a control valve of NPS 1 or smaller it may be a stop and waste valve |
| Risers | A shut-off valve at the source of supply, except risers serving only one dwelling unit |
| Each dwelling unit in a multi-unit residential building | A shut-off valve where the supply enters the unit |
| Non-residential buildings | A shut-off valve for every fixture, or for each group of fixtures in one room |
| Every water closet | Its own shut-off valve on the supply pipe |
| Public washrooms | Every fixture individually valved, each valve accessible (7.6.1.3A.OBC Div. B 7.6.1.3A. Public Washrooms(1) The water supply to each fixture in a washroom for public use shall be individually valved and each valve shall be accessible.) |
| Tanks, pressure vessels, appliances | A shut-off valve close to the item (7.6.1.3B.OBC Div. B 7.6.1.3B. Tanks(1) Every water pipe that supplies a hot water tank, pressure vessel, plumbing appliance or water using device shall be provided with a shut-off valve located close to the tank, pressure vessel, plumbing appliance or water using device.) |
Two other arrangement rules apply mainly to larger buildings. A hot water system with a developed length over 30 m, or one serving more than 4 storeys, must keep its temperature up by recirculation or by self-regulating heat tracing (7.6.1.1.(2)OBC Div. B 7.6.1.1. Design(1) Fixtures supplied with separate hot and cold water controls shall have the hot water control on the left and the cold on the right. (1.1) Where hot and cold water are mixed and the temperature is regulated by a single, unmarked, manual control, a movement to the left shall increase the temperature and a movement…). And where plastic pipe rated for cold water only is used for the water service, a check valve goes at the building end (7.6.1.5.OBC Div. B 7.6.1.5. Check Valves(1) A check valve shall be installed at the building end of a water service pipe where the pipe is made of plastic that is suitable for cold water use only.).
For relief valves, a pressure vessel's relief valve must keep tank pressure at or below the lesser of 1,100 kPa and half the tank's maximum test pressure. The temperature-relief element sits in the top 150 mm and keeps the water below 99°C. Discharge pipes are rigid, full size, slope down, have no thread at the outlet and end with an air break of not more than 300 mm. No shut-off valve may be installed between a tank and its relief valves or on their discharge (7.6.1.7.OBC Div. B 7.6.1.7. Relief Valves(1) Every pressure vessel that is part of a plumbing system or connected to a plumbing system shall be equipped with a pressure-relief valve designed to open when the water pressure in the tank reaches the rated working pressure of the tank, and so located that the pressure in the tank shall not exceed 1,100 kPa or…).
Backflow prevention
The general rule is that nothing non-potable may get into the potable system (7.6.2.1.OBC Div. B 7.6.2.1. Connection of Systems(1) Connections to potable water systems shall be designed and installed so that non-potable water or substances that may render the water non-potable cannot enter the system. (2) Reserved. (3) Backflow preventers shall be selected and installed in conformance with CSA B64.10, "Selection and installation of backflow…). Backflow preventers are selected and installed under CSA B64.10, and you may not connect a system fed from a drinking water system to any other potable system without the water purveyor's consent. Back-siphonage protection is needed for any fixture or tank not under pressure above atmospheric, and backflow protection where the supply connects to a boiler, cooling jacket, lawn sprinkler or similar device (7.6.2.2.OBC Div. B 7.6.2.2. Back-Siphonage(1) Every potable water system that supplies a fixture or tank that is not subject to pressures above atmospheric shall be protected against back-siphonage by a backflow preventer. (2) Where a potable water supply is connected to a boiler, tank, cooling jacket, lawn sprinkler system or other device where a non-potable…).
Fire sprinkler and standpipe connections
Article 7.6.2.4.OBC Div. B 7.6.2.4. Backflow from Fire Protection Systems(1) A backflow preventer shall not be required in residential full flow-through fire sprinkler/standpipe systems in which the pipes and fittings are constructed of potable water system materials. (2) Except as required by Sentence (4), potable water system connections to fire sprinkler and standpipe systems shall be… is a favourite PAB question because it reads like a decision table. In our words:
| System | Minimum protection |
|---|---|
| Residential full flow-through, potable materials | None required |
| Residential partial flow-through, potable materials | Dual check valve (DuC or DuCF) |
| Class 1, no additives, all potable materials | Single or dual check (SCVAF or DuC) |
| Other Class 1, and Class 2 and 3, no additives | Double check valve (DCVA or DCVAF) |
| Class 1, 2 or 3 with antifreeze or other additives | RP device on the additive portion, rest per the no-additive rule |
| Class 4 and Class 5 | Reduced pressure principle (RP or RPF) |
| Class 6 | Double check valve, or RP where a potentially severe health hazard exists |
These devices go upstream of the fire department pumper connection. Where an RP device is required on the water service at a fire service connection on the same premises, an RPF is also required on the fire service connection for Class 3 to 6 systems.
Premise isolation
Where a moderate or severe hazard may be caused by backflow, the whole building gets premise isolation with a backflow preventer selected under CSA B64.10 (7.6.2.6.OBC Div. B 7.6.2.6. Premise Isolation(1) Buildings or facilities where a moderate hazard or severe hazard may be caused by backflow shall be provided with premise isolation of the potable water system by the installation of a backflow preventer selected in accordance with Clauses 5.3.4.2.(b) and (c) of CSA B64.10, "Selection and installation of backflow…). Part 9 residential buildings are exempt unless they have access to an "auxiliary water supply" (a defined term: any water supply available on the premises other than the primary potable supply). Where there is no direct connection between the auxiliary supply and the potable system, a dual check valve (DuC) is enough. The hazard classification itself is in CSA B64.10, not in the Compendium.
Air gaps and vacuum breakers
An air gap is at least 25 mm and at least twice the diameter of the outlet opening, and may not be in a noxious environment (7.6.2.9.OBC Div. B 7.6.2.9. Air Gap(1) An air gap shall not be located in a noxious environment. (2) Air gaps shall be not less than 25 mm high and at least twice the diameter of the opening of the water supply outlet in height.). An atmospheric vacuum breaker goes downstream of the control valve, is under pressure only while the valve is open and for no more than 12 h of continuous use, with its critical level at least 25 mm above the flood level rim. A pressure vacuum breaker needs 300 mm (7.6.2.10.OBC Div. B 7.6.2.10. Vacuum Breakers(1) Where the critical level is not marked on an atmospheric vacuum breaker, pressure vacuum breaker or spill-resistant pressure vacuum breaker, the critical level shall be taken as the lowest point on the device. (2) Where an atmospheric vacuum breaker is installed, it shall be located on the downstream side of the…). If the critical level is not marked, use the lowest point of the device.
Size and capacity of pipes
Pipe sizing in larger buildings is an engineering exercise: systems must deliver peak demand at the fitting manufacturer's flow pressures, following good engineering practice such as the ASHRAE and ASPE handbooks (7.6.3.1.OBC Div. B 7.6.3.1. Design, Fabrication and Installation(1) Water distribution systems shall be designed to provide peak demand flow when the flow pressures at the supply openings conform to the plumbing supply fitting manufacturer's specifications. (2) Potable water systems shall be designed, fabricated and installed in accordance with good engineering practice, such as…). The Code tables supply the fixture unit loads.
- Table 7.6.3.2.-AOBC Div. B Table 7.6.3.2-A. Sizing of Water Distribution Systems[1][2]Table 7.6.3.2.-A — Sizing of Water Distribution Systems[1][2] Forming Part of Sentences 7.6.3.2.(1), (2) and (3) and 7.6.3.4.(2), (3) and (5) Fixture or Device | Minimum Nominal Pipe Size of Supply Pipe, NPS | Private Use Hydraulic Load, fixture units: Cold | Private Use Hydraulic Load, fixture units: Hot | Private… gives the minimum supply size and the private and public use loads for each fixture. Public use loads are often higher: a 6 LPF tank water closet is 2.2 either way, but a lavatory of 8.3 LPM or less is 0.7 private and 2 public.
- Flush valve water closets and urinals use the accumulative values in Table 7.6.3.2.-COBC Div. B Table 7.6.3.2-C. Sizing of Water Distribution Systems for Water Closets with Direct Flush ValvesTable 7.6.3.2.-C — Sizing of Water Distribution Systems for Water Closets with Direct Flush Valves Forming Part of Sentences 7.6.3.2.(4) and 7.6.3.4.(5) Number of Valves | Individual Fixture Units Assigned in Decreasing Values | Fixture Units in Accumulative Values[1] 1 | 40 | 40 2 | 30 | 70 3 | 20 | 90 4 | 15 | 105 5… and Table 7.6.3.2.-BOBC Div. B Table 7.6.3.2-B. Sizing of Water Distribution Systems for Urinals with Direct Flush ValvesTable 7.6.3.2.-B — Sizing of Water Distribution Systems for Urinals with Direct Flush Valves Forming Part of Sentences 7.6.3.2.(4) and 7.6.3.4.(5) Number of Valves | Individual Fixture Units Assigned in Decreasing Values | Fixture Units in Accumulative Values[1] 1 | 20 | 20 2 | 15 | 35 3 | 10 | 45 4 | 8 | 53 5 or more…. Do not multiply the first value by the number of valves.
- Fixtures not listed take a load from the supply pipe size in Table 7.6.3.2.-DOBC Div. B Table 7.6.3.2-D. Hydraulic Loads of Fixtures Not Listed in Table 7.6.3.2.-ATable 7.6.3.2.-D — Hydraulic Loads of Fixtures Not Listed in Table 7.6.3.2.-A Forming Part of Sentences 7.6.3.2.(2) and (3) and 7.6.3.4.(5) Nominal Pipe Size of Supply Pipe, NPS | Hydraulic Load, fixture units — Private Use | Hydraulic Load, fixture units — Public Use ⅜ | 1 | 2 ½ | 2 | 4 ¾ | 3 | 6 1 | 6 | 10.
- With a detailed engineering method, separate hot and cold demands are 75% of the fixture's load (7.6.3.2.(3)OBC Div. B 7.6.3.2. Hydraulic Load(1) Except as provided in Sentence (3), the hydraulic load of a fixture or device that is listed in Table 7.6.3.2.-A shall be the number of fixture units given in the Table. (2) Except as provided in Sentences (1) and (3), the hydraulic load of a fixture that is not listed in Table 7.6.3.2.-A is the number of fixture…).
The velocity-based Table 7.6.3.4.OBC Div. B Table 7.6.3.4. Hydraulic Load, Fixture UnitsTable 7.6.3.4. — Hydraulic Load, Fixture Units Forming Part of Sentence 7.6.3.4.(5) Nominal Pipe Size of Water Pipe, NPS | Water Velocity, 3.0 m/s[1]: Hydraulic Load, fixture units | Water Velocity, 2.4 m/s[1]: Hydraulic Load, fixture units | Water Velocity, 1.5 m/s[1]: Hydraulic Load, fixture units ½ | 8 | 7 | 4 ¾ |… is a simplified method only for buildings with one or two dwelling units, or row houses with separate services, where pressure at entry is at least 200 kPa and the system is not over 90 m long (7.6.3.4.(5)OBC Div. B 7.6.3.4. Size(1) Water service pipes shall be sized according to the peak demand flow but shall not be less than NPS3/4 . (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…). A water service is never smaller than NPS 3/4 (7.6.3.4.(1)OBC Div. B 7.6.3.4. Size(1) Water service pipes shall be sized according to the peak demand flow but shall not be less than NPS3/4 . (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…), and static pressure at a fixture above 550 kPa needs a pressure-reducing valve (7.6.3.3.OBC Div. B 7.6.3.3. Static Pressure(1) Where the static pressure at any fixture may exceed 550 kPa, a pressure-reducing valve shall be installed to limit the maximum static pressure at the fixture to 550 kPa.).
Water efficiency
Flush volumes are capped at 6.0 LPF for water closets and 1.9 LPF for urinals, and Group C buildings drop water closets to 4.8 LPF (dual flush 4.1/6.0 is deemed to comply) (7.6.1.6.OBC Div. B 7.6.1.6. Flushing Devices(1) Flushing devices that serve water closets or urinals shall have sufficient capacity and be adjusted to deliver at each operation a volume of water that will thoroughly flush the fixture or fixtures they serve. (2) Where a manually operated flushing device is installed, it shall serve only one fixture. (3) Except…). Flush-tank urinals need a device that stops flushing when they are not in use, and a manually operated flushing device serves one fixture only. In public washrooms, each lavatory needs automatic shut-off, and multiple shower heads on one temperature control each need automatic shut-off (7.6.4.1.OBC Div. B 7.6.4.1. Water Supply Fittings(1) Each lavatory in a washroom with fixtures for public use shall be equipped with a device capable of automatically shutting off the flow of water when the lavatory is not in use. (See Note A-7.6.4.1.(1) and (3)) (2) An automatic compensating valve serving an individual shower head shall have a manufacturer's…).
Common traps
- Applying Table 7.6.3.4. to an apartment building. It is limited to one or two dwelling units or row houses with separate services.
- Adding 40 per flush valve water closet. Use the accumulative column.
- Forgetting the 25 mm minimum when the outlet is small, or using 25 mm for a pressure vacuum breaker (it is 300 mm).
- Choosing an RP for every fire system. Only additives, Class 4, Class 5 and severe-hazard Class 6 need one.
Chapter review
Chapter at a glance
One line per section: the idea to carry into the exam. Then the answers that most often catch candidates out.
- Arrangement of piping and valves
Valve rules are the most common lookup questions in this section.
- Backflow prevention
The general rule is that nothing non-potable may get into the potable system.
- Size and capacity of pipes
Pipe sizing in larger buildings is an engineering exercise: systems must deliver peak demand at the fitting manufacturer's flow pressures, following good engineering practice such…
- Water efficiency
Flush volumes are capped at 6.0 LPF for water closets and 1.9 LPF for urinals, and Group C buildings drop water closets to 4.8 LPF (dual flush 4.1/6.0 is deemed to comply).
Usual exam traps
- Applying Table 7.6.3.4. to an apartment building. It is limited to one or two dwelling units or row houses with separate services.
- Adding 40 per flush valve water closet. Use the accumulative column.
- Forgetting the 25 mm minimum when the outlet is small, or using 25 mm for a pressure vacuum breaker (it is 300 mm).
- Choosing an RP for every fire system. Only additives, Class 4, Class 5 and severe-hazard Class 6 need one.
Practice this chapter
Questions on Potable water systems (7.6), in the exam format, every answer explained and cited to its article. Sign in to start; a free account gets the free questions.
Code cited in this chapter
Based on the official 2024 Building Code Compendium on ontario.ca.
© King's Printer for Ontario, 2024. Reproduced with permission.
OBC Div. B 7.6.1.3. Control and Shut-Off Valves
Open OBC Div. B 7.6.1.3. in the code viewer(1)A building control valve shall be provided
(a)on every water service pipe at the location where the water service pipe enters the building, or
(b)on the water distribution system at a location immediately downstream of the point of entry treatment unit, where the building is served by a point of entry treatment unit located in the building.
(2)Pipes that convey water from a gravity water tank or from a private water supply system shall be fitted with a shut-off valve at the source of supply.
(2.1)Except as provided in Sentence (2.2), a drain port shall be provided on the water distribution system immediately downstream of the building control valve required by Sentence (1) and if there is a meter, the drain port shall be installed immediately downstream of the meter on the water distribution system.
(2.2)Where the building control valve required by Sentence (1) is of NPS 1 or smaller, the drain port may be an integral part of the building control valve in the form of a stop and waste valve and the drain port shall be located on the water distribution system side of the stop and waste valve.
(3)Except for risers that serve only one dwelling unit, risers shall be provided with a shut-off valve located at the source of supply.
(4)Water closets shall be provided with a shut-off valve on their water supply pipe.
(5)In buildings of residential occupancy that contain more than one dwelling unit, a shut-off valve shall be installed where the water supply enters each dwelling unit, so that, when the water supply to one suite is shut off, the water supply to the remainder of the building is not interrupted.
(6)In buildings of other than residential occupancy, shut-off valves shall be provided on the water supply to
(a)every fixture, or
(b)any group of fixtures in the same room, except as provided in Sentence (4).
(7)Pipes that supply water to a hot water tank shall be provided with a shut-off valve located close to the tank.
(8)Where the water supply is to be metered, the installation of the meter, including the piping that is part of the meter installation and the valving arrangement for the meter installation, shall be according to the water purveyor's requirements.
(9)For the purpose of identifying the pipe material where plastic water pipe is used underground for a service pipe, the end of the pipe inside the building shall be brought above ground for a distance not less than 300 mm and not greater than 450 mm.
OBC Div. B 7.6.1.3A. Public Washrooms
Open OBC Div. B 7.6.1.3A. in the code viewer(1)The water supply to each fixture in a washroom for public use shall be individually valved and each valve shall be accessible.
OBC Div. B 7.6.1.3B. Tanks
Open OBC Div. B 7.6.1.3B. in the code viewer(1)Every water pipe that supplies a hot water tank, pressure vessel, plumbing appliance or water using device shall be provided with a shut-off valve located close to the tank, pressure vessel, plumbing appliance or water using device.
OBC Div. B 7.6.1.1. Design
Open OBC Div. B 7.6.1.1. in the code viewer(1)Fixtures supplied with separate hot and cold water controls shall have the hot water control on the left and the cold on the right.
(1.1)Where hot and cold water are mixed and the temperature is regulated by a single, unmarked, manual control, a movement to the left shall increase the temperature and a movement to the right shall decrease the temperature.
(2)In a hot water distribution system of a developed length of more than 30 m or supplying more than 4 storeys, the water temperature shall be maintained by
(a)recirculation, or
(b)a self-regulating heat tracing system.
OBC Div. B 7.6.1.5. Check Valves
Open OBC Div. B 7.6.1.5. in the code viewer(1)A check valve shall be installed at the building end of a water service pipe where the pipe is made of plastic that is suitable for cold water use only.
OBC Div. B 7.6.1.7. Relief Valves
Open OBC Div. B 7.6.1.7. in the code viewer(1)Every pressure vessel that is part of a plumbing system or connected to a plumbing system shall be equipped with a pressure-relief valve designed to open when the water pressure in the tank reaches the rated working pressure of the tank, and so located that the pressure in the tank shall not exceed 1,100 kPa or one-half the maximum test pressure sustained by the tank, whichever is the lesser.
(2)The hot water tank of a storage-type service water heater shall be equipped with a temperature-relief valve with a temperature-sensing element
(a)located within the top 150 mm of the tank, and
(b)designed to open and discharge sufficient water from the tank to keep the temperature of the water in the tank from exceeding 99°C under all operating conditions.
(3)A pressure-relief valve and temperature-relief valve may be combined where Sentences (1) and (2) are complied with.
(4)Indirect service water heaters shall be equipped with
(a)a pressure-relief valve, and
(b)a temperature-relief valve on every storage tank that forms part of the system.
(5)Pipes that convey water from a temperature-relief, pressure-relief, or a combined temperature- and pressure-relief valve shall
(a)be of a nominal pipe size at least equal to the NPS of the outlet of the valve,
(b)be rigid, slope downward from the valve, and terminate with an indirect connection above a floor drain, sump, or other safe location, with an air break of not more than 300 mm,
(c)have no thread at its outlet, and
(d)be capable of operating at a temperature of not less than 99°C. (See Note A-7.6.1.7.(5))
(6)The temperature-relief valve required in Clause (4)(b) shall
(a)have a temperature-sensing element located within the top 150 mm of the tank, and
(b)be designed to open and discharge sufficient water to keep the temperature of the water in the tank from exceeding 99°C under all operating conditions.
(7)No shut-off valve shall be installed on the pipe between any tank and the relief valves or on the discharge lines from such relief valves.
OBC Div. B 7.6.2.1. Connection of Systems
Open OBC Div. B 7.6.2.1. in the code viewer(1)Connections to potable water systems shall be designed and installed so that non-potable water or substances that may render the water non-potable cannot enter the system.
(2)Reserved.
(3)Backflow preventers shall be selected and installed in conformance with CSA B64.10, "Selection and installation of backflow preventers."
(3.1)No connection shall be made between a potable water system supplied with water from a drinking water system and any other potable water system without the consent of the water purveyor.
OBC Div. B 7.6.2.2. Back-Siphonage
Open OBC Div. B 7.6.2.2. in the code viewer(1)Every potable water system that supplies a fixture or tank that is not subject to pressures above atmospheric shall be protected against back-siphonage by a backflow preventer.
(2)Where a potable water supply is connected to a boiler, tank, cooling jacket, lawn sprinkler system or other device where a non-potable fluid may be under pressure that is above atmospheric or the water outlet may be submerged in the non-potable fluid, the water supply shall be protected against backflow by a backflow preventer.
Show all 23 articles
OBC Div. B 7.6.2.4. Backflow from Fire Protection Systems
Open OBC Div. B 7.6.2.4. in the code viewer(1)A backflow preventer shall not be required in residential full flow-through fire sprinkler/standpipe systems in which the pipes and fittings are constructed of potable water system materials.
(2)Except as required by Sentence (4), potable water system connections to fire sprinkler and standpipe systems shall be protected against backflow caused by back-siphonage or back pressure in conformance with Clauses (a) to (g), as applicable:
(a)residential partial flow-through fire sprinkler/standpipe systems in which the pipes and fittings are constructed of potable water system materials shall be protected by a dual check valve backflow preventer conforming to
(i)CSA B64.6, "Dual check valve (DuC) backflow preventers," or
(ii)CSA B64.6.1, "Dual check valve backflow preventers for fire protection systems (DuCF),"
(b)provided that the systems do not use antifreeze or other additives of any kind and that all pipes and fittings are constructed of potable water system materials, Class 1 fire sprinkler/standpipe systems shall be protected by a single or dual check valve backflow preventer conforming to
(i)CSA B64.6, "Dual check valve (DuC) backflow preventers," or
(ii)CSA B64.9, "Single check valve backflow preventers for fire protection systems (SCVAF),"
(c)provided that the systems do not use antifreeze or other additives of any kind, Class 1 fire sprinkler/standpipe systems not covered by Clause (b) as well as Class 2 and Class 3 fire sprinkler/standpipe systems shall be protected by a double check valve backflow preventer conforming to
(i)CSA B64.5, "Double check valve (DCVA) backflow preventers," or
(ii)CSA B64.5.1, "Double check valve backflow preventers for fire protection systems (DCVAF),"
(d)Class 1, Class 2 or Class 3 fire sprinkler/standpipe systems in which antifreeze or other additives are used shall be protected by a reduced pressure principle backflow preventer conforming to
(i)CSA B64.4, "Reduced pressure principle (RP) backflow preventers," or
(ii)CSA B64.4.1, "Reduced pressure principle backflow preventers for fire protection systems (RPF)," installed on the portion of the system that uses the additives and the balance of the system shall be protected as required by Clause (b) or (c),
(e)Class 4 and Class 5 fire sprinkler/standpipe systems shall be protected by a reduced pressure principle backflow preventer conforming to
(i)CSA B64.4, "Reduced pressure principle (RP) backflow preventers," or
(ii)CSA B64.4.1, "Reduced pressure principle backflow preventers for fire protection systems (RPF),"
(f)Class 6 fire sprinkler/standpipe systems shall be protected by a double check valve backflow preventer conforming to
(i)CSA B64.5, "Double check valve (DCVA) backflow preventers," or
(ii)CSA B64.5.1, "Double check valve backflow preventers for fire protection systems (DCVAF)."
(g)where a potentially severe health hazard may be caused by backflow, Class 6 fire sprinkler/standpipe systems shall be protected by a reduced pressure principle backflow preventer conforming to
(i)CSA B64.4, "Reduced pressure principle (RP) backflow preventers," or
(ii)CSA B64.4.1, "Reduced pressure principle backflow preventers for fire protection systems (RPF)."
(3)Backflow preventers required by Sentence (2) shall be installed upstream of the fire department pumper connection.
(4)Where a reduced pressure principle backflow preventer is required on a water service pipe at a fire service connection located on the same premises as the fire service pipe in Class 3, 4, 5 and 6 fire sprinkler/standpipe systems, a reduced pressure principle backflow preventer conforming to CSA B64.4.1, "Reduced pressure principle backflow preventers for fire protection systems (RPF)," shall also be required on the fire service connection.
OBC Div. B 7.6.2.6. Premise Isolation
Open OBC Div. B 7.6.2.6. in the code viewer(1)Buildings or facilities where a moderate hazard or severe hazard may be caused by backflow shall be provided with premise isolation of the potable water system by the installation of a backflow preventer selected in accordance with Clauses 5.3.4.2.(b) and (c) of CSA B64.10, "Selection and installation of backflow preventers."
(2)Buildings of residential occupancy within the scope of Part 9 are not required to be isolated unless they have access to an auxiliary water supply.
(3)Except as provided in Sentence (1), where no direct connection exists between the auxiliary water supply and the potable water system, premise isolation shall be provided by a dual check valve backflow preventer conforming to CSA B64.6, "Dual check valve (DuC) backflow preventers."
OBC Div. B 7.6.2.9. Air Gap
Open OBC Div. B 7.6.2.9. in the code viewer(1)An air gap shall not be located in a noxious environment.
(2)Air gaps shall be not less than 25 mm high and at least twice the diameter of the opening of the water supply outlet in height.
OBC Div. B 7.6.2.10. Vacuum Breakers
Open OBC Div. B 7.6.2.10. in the code viewer(1)Where the critical level is not marked on an atmospheric vacuum breaker, pressure vacuum breaker or spill-resistant pressure vacuum breaker, the critical level shall be taken as the lowest point on the device.
(2)Where an atmospheric vacuum breaker is installed, it shall be located on the downstream side of the fixture control valve or faucet so that it will be subject to water supply pressure
(a)only when the valve or faucet is open, and
(b)for periods of continuous use not exceeding 12 h.
(3)An atmospheric vacuum breaker shall be installed so that the critical level is at least the distance specified by the manufacturer for safe operation of the device, but not less than 25 mm above
(a)the flood level rim of a fixture or tank, or
(b)the highest point open to the atmosphere in an irrigation system.
(4)A pressure vacuum breaker or spill-resistant pressure vacuum breaker shall be installed so that the critical level is not less than 300 mm above
(a)the flood level rim of a fixture or tank, or
(b)the highest point open to the atmosphere in an irrigation system.
OBC Div. B 7.6.3.1. Design, Fabrication and Installation
Open OBC Div. B 7.6.3.1. in the code viewer(1)Water distribution systems shall be designed to provide peak demand flow when the flow pressures at the supply openings conform to the plumbing supply fitting manufacturer's specifications.
(2)Potable water systems shall be designed, fabricated and installed in accordance with good engineering practice, such as that described in the ASHRAE Handbooks and ASPE Plumbing Engineering Design Handbooks.
(3)Reserved.
(4)Pipes that supply a fixture shall have a capacity that will produce a flow in the fixture that will flush the fixture and keep it in a sanitary condition.
OBC Div. B Table 7.6.3.2-A. Sizing of Water Distribution Systems[1][2]
Open OBC Div. B Table 7.6.3.2-A. in the code viewerTable 7.6.3.2.-A — Sizing of Water Distribution Systems[1][2] Forming Part of Sentences 7.6.3.2.(1), (2) and (3) and 7.6.3.4.(2), (3) and (5) Fixture or Device | Minimum Nominal Pipe Size of Supply Pipe, NPS | Private Use Hydraulic Load, fixture units: Cold | Private Use Hydraulic Load, fixture units: Hot | Private Use Hydraulic Load, fixture units: Total | Public Use Hydraulic Load, fixture units: Cold | Public Use Hydraulic Load, fixture units: Hot | Public Use Hydraulic Load, fixture units: Total Bathroom group with 6 LPF flush tank[3] | N/A | 2.7 | 1.5 | 3.6 | N/A | N/A | N/A Bathroom group with greater than 6 LPF flush tank[3] | N/A | 4 | 3 | 6 | N/A | N/A | N/A Bathroom group with more than 3 fixtures[4] | N/A | N/A | N/A | N/A | N/A | N/A | N/A Bathtub with or without shower head | ½ | 1 | 1 | 1.4 | 3 | 3 | 4 Bathtub with NPS ¾ spout | ¾ | 7.5 | 7.5 | 10 | 7.5 | 7.5 | 10 Bedpan washer | 1 | N/A | N/A | N/A | 7.5 | 7.5 | 10 Bidet | ⅜ | 1.5 | 1.5 | 2 | N/A | N/A | N/A Clothes washer, 3.5 kg | ½ | 1 | 1 | 1.4 | 2.25 | 2.25 | 3 Clothes washer, 6.8 kg | ½ | N/A | N/A | N/A | 3 | 3 | 4 Clothes washer, commercial[5] | N/A | N/A | N/A | N/A | N/A | N/A | N/A Dental lavatory | ⅜ | N/A | N/A | N/A | 1.5 | 1.5 | 2 Dental unit, cuspidor | ⅜ | N/A | N/A | N/A | 1 | N/A | 1 Dishwasher, commercial[5] | N/A | N/A | N/A | N/A | N/A | N/A | N/A Dishwasher, domestic | ⅜ | N/A | 1.4 | 1.4 | N/A | N/A | N/A Drinking fountain or water cooler | ⅜ | N/A | N/A | N/A | 0.25 | N/A | 0.25 Hose bibb | ½ | 2.5 | N/A | 2.5 | 2.5 | N/A | 2.5 Hose bibb | ¾ | 3 | N/A | 3 | 6 | N/A | 6 Hose bibb, combination hot and cold | ½ | 1.9 | 1.9 | 2.5 | 1.9 | 1.9 | 2.5 Lavatory, 8.3 LPM or less | ⅜ | 0.5 | 0.5 | 0.7 | 1.5 | 1.5 | 2 Lavatory, greater than 8.3 LPM | ⅜ | 0.75 | 0.75 | 1 | 1.5 | 1.5 | 2 Shower head, 9.5 LPM or less per head | ½ | 1 | 1 | 1.4 | 3 | 3 | 4 Shower head, greater than 9.5 LPM per head | ½ | 1.5 | 1.5 | 2 | 3 | 3 | 4 Shower, spray, multi-head, fixture unit per head | [5] | 1 | 1 | 1.4 | 3 | 3 | 4 Sink, bar | ⅜ | 0.75 | 0.75 | 1 | 1.5 | 1.5 | 2 Sink, clinic service faucet | ½ | N/A | N/A | N/A | 2.25 | 2.25 | 3 Sink, clinic service with direct flush valve | 1 | N/A | N/A | N/A | 6 | N/A | 6 Sink, kitchen, commercial, per faucet | ½ | N/A | N/A | N/A | 3 | 3 | 4 Sink, kitchen, domestic, 8.3 LPM or less | ⅜ | 1 | 1 | 1.4 | 1 | 1 | 1.4 Sink, kitchen, domestic, greater than 8.3 LPM | ⅜ | 1.5 | 1.5 | 2 | 1.5 | 1.5 | 2 Sink, laboratory | ⅜ | N/A | N/A | N/A | 1.5 | 1.5 | 2 Sink, laundry (1 or 2 compartments) | ⅜ | 1 | 1 | 1.4 | 1 | 1 | 1.4 Sink, service or mop basin | ½ | N/A | N/A | N/A | 2.25 | 2.25 | 3 Sink, washup, per faucet | ½ | N/A | N/A | N/A | 1.5 | 1.5 | 2 Urinal, with direct flush valve | ¾ | [6] | N/A | [6] | [6] | N/A | [6] Urinal, with flush tank | ⅜ | 3 | N/A | 3 | 3 | N/A | 3 Urinal, with self-closing metering valve | ½ | 2 | N/A | 2 | 4 | N/A | 4 Water closet, 6 LPF or less with flush tank | ⅜ | 2.2 | N/A | 2.2 | 2.2 | N/A | 2.2 Water closet, greater than 6 LPF with flush tank | ⅜ | 3 | N/A | 3 | 5 | N/A | 5 Water closet, with direct flush valve | 1 | [6] | N/A | [6] | [6] | N/A | [6] Notes to Table 7.6.3.2.-A: (1) The fixture unit values in this Table are not applicable in certain assembly occupancies because of surges in use by the occupants. For such occupancies, refer to specific design information. (2) For fixtures not indicated in this Table, refer to Table 7.6.3.2.-D. (3) Bathroom group is based on NPS ½ bathtub supply pipe. (4) Add additional fixture to the fixture load for bathroom group. (5) Refer to the manufacturer's recommendations. (6) For fixture unit values for fixtures with direct flush valves, see Sentence 7.6.3.2.(4) and Tables 7.6.3.2.-B and 7.6.3.2.-C.
OBC Div. B Table 7.6.3.2-C. Sizing of Water Distribution Systems for Water Closets with Direct Flush Valves
Open OBC Div. B Table 7.6.3.2-C. in the code viewerTable 7.6.3.2.-C — Sizing of Water Distribution Systems for Water Closets with Direct Flush Valves Forming Part of Sentences 7.6.3.2.(4) and 7.6.3.4.(5) Number of Valves | Individual Fixture Units Assigned in Decreasing Values | Fixture Units in Accumulative Values[1] 1 | 40 | 40 2 | 30 | 70 3 | 20 | 90 4 | 15 | 105 5 or more | 10 for each public use | 115, plus 10 for each public use additional fixture in excess of 5 5 or more | 6 for each private use | 111, plus 6 for each private use additional fixture in excess of 5 Notes to Table 7.6.3.2.-C: (1) The accumulative fixture unit values are the total values to be used in conjunction with Table 7.6.3.2.-A.
OBC Div. B Table 7.6.3.2-B. Sizing of Water Distribution Systems for Urinals with Direct Flush Valves
Open OBC Div. B Table 7.6.3.2-B. in the code viewerTable 7.6.3.2.-B — Sizing of Water Distribution Systems for Urinals with Direct Flush Valves Forming Part of Sentences 7.6.3.2.(4) and 7.6.3.4.(5) Number of Valves | Individual Fixture Units Assigned in Decreasing Values | Fixture Units in Accumulative Values[1] 1 | 20 | 20 2 | 15 | 35 3 | 10 | 45 4 | 8 | 53 5 or more | 5 each | 58, plus 5 for each additional fixture in excess of 5 Notes to Table 7.6.3.2.-B: (1) The accumulative fixture unit values are the total values to be used in conjunction with Table 7.6.3.2.-A.
OBC Div. B Table 7.6.3.2-D. Hydraulic Loads of Fixtures Not Listed in Table 7.6.3.2.-A
Open OBC Div. B Table 7.6.3.2-D. in the code viewerTable 7.6.3.2.-D — Hydraulic Loads of Fixtures Not Listed in Table 7.6.3.2.-A Forming Part of Sentences 7.6.3.2.(2) and (3) and 7.6.3.4.(5) Nominal Pipe Size of Supply Pipe, NPS | Hydraulic Load, fixture units — Private Use | Hydraulic Load, fixture units — Public Use ⅜ | 1 | 2 ½ | 2 | 4 ¾ | 3 | 6 1 | 6 | 10
OBC Div. B 7.6.3.2. Hydraulic Load
Open OBC Div. B 7.6.3.2. in the code viewer(1)Except as provided in Sentence (3), the hydraulic load of a fixture or device that is listed in Table 7.6.3.2.-A shall be the number of fixture units given in the Table.
(2)Except as provided in Sentences (1) and (3), the hydraulic load of a fixture that is not listed in Table 7.6.3.2.-A is the number of fixture units listed in Table 7.6.3.2.-D.
(3)Where fixtures are supplied with both hot and cold water, the hydraulic loads for maximum separate demands shall be 75% of the hydraulic load of the fixture units given in Tables 7.6.3.2.-A and 7.6.3.2.-D when using a detailed engineering design method.
(4)The hydraulic load of urinals and water closets with direct flush valves shall be the number of fixture units listed in Tables 7.6.3.2.-B and 7.6.3.2.-C. (See Note A-7.6.3.2.(4))
OBC Div. B Table 7.6.3.4. Hydraulic Load, Fixture Units
Open OBC Div. B Table 7.6.3.4. in the code viewerTable 7.6.3.4. — Hydraulic Load, Fixture Units Forming Part of Sentence 7.6.3.4.(5) Nominal Pipe Size of Water Pipe, NPS | Water Velocity, 3.0 m/s[1]: Hydraulic Load, fixture units | Water Velocity, 2.4 m/s[1]: Hydraulic Load, fixture units | Water Velocity, 1.5 m/s[1]: 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).
OBC Div. B 7.6.3.4. Size
Open OBC Div. B 7.6.3.4. in the code viewer(1)Water service pipes shall be sized according to the peak demand flow but shall not be less than NPS3/4 .
(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 NPS3/8 supply pipe, a connector not more than 750 mm long and not less than NPS1/4 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 3/4.
(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.
OBC Div. B 7.6.3.3. Static Pressure
Open OBC Div. B 7.6.3.3. in the code viewer(1)Where the static pressure at any fixture may exceed 550 kPa, a pressure-reducing valve shall be installed to limit the maximum static pressure at the fixture to 550 kPa.
OBC Div. B 7.6.1.6. Flushing Devices
Open OBC Div. B 7.6.1.6. in the code viewer(1)Flushing devices that serve water closets or urinals shall have sufficient capacity and be adjusted to deliver at each operation a volume of water that will thoroughly flush the fixture or fixtures they serve.
(2)Where a manually operated flushing device is installed, it shall serve only one fixture.
(3)Except as provided in Sentence (4), water closets and urinals shall have an integral means of limiting the maximum amount of water used in each flush cycle to that specified in Table 7.6.1.6.-A.
(4)In buildings classified as Group C occupancy, the flush cycle for each fixture that is a water closet or urinal shall not exceed the maximum water used in each flush cycle listed for that fixture in Table 7.6.41.6.-B.
(4.1)Sentences (3) and (4) do not apply to a fixture located in an existing building where the chief building official is satisfied that compliance with the requirement is impracticable because of maintenance or operational difficulties. (See Note A-7.6.1.6.(4.1))
(5)Flush-tank-type urinals shall be equipped with a device capable of preventing flush cycles when they are not in use.
OBC Div. B 7.6.4.1. Water Supply Fittings
Open OBC Div. B 7.6.4.1. in the code viewer(1)Each lavatory in a washroom with fixtures for public use shall be equipped with a device capable of automatically shutting off the flow of water when the lavatory is not in use. (See Note A-7.6.4.1.(1) and (3))
(2)An automatic compensating valve serving an individual shower head shall have a manufacturer's minimum-rated water flow rate equal to or less than the shower head it serves. (See Note A-7.6.4.1.(2))
(3)Where multiple shower heads installed in a public showering facility are served by one temperature control, each shower head shall be equipped with a device capable of automatically shutting off the flow of water when the shower head is not in use. (See Note A-7.6.4.1.(1) and (3))