Plumbing connections to sewage systems (Part 7) (On-site Sewage Systems)

Last updated October 22, 2026

Values this chapter turns on

water service to a private sewage system, horizontal: 2,440 mm; water service to a private sewage system, horizontal
inside this, water service is one jointless run: 15 m; inside this, water service is one jointless run
tamped stone-free backfill over buried pipe: 300 mm; tamped stone-free backfill over buried pipe
minimum slope for drainage pipe of NPS 3 or less: 1 in 50; minimum slope for drainage pipe of NPS 3 or less

The sewage system starts where the building sewer ends, but the exam does not stop at the tank inlet. It tests the Part 7 rules that most affect a septic installation: what may go into the drain, how buried pipe is protected, how far the water service must stay from the system, and how fixture units are counted. Fixture units matter twice in Part 8: for extra house flow over 20 fixture units, and for Class 2 greywater flows.

Floor drains, service connections and private sewers

A floor drain is required in a basement that is part of a dwelling unit where gravity drainage to a sanitary drainage system is possible. If gravity drainage is not possible, it may go to a storm system, dry well or ditch, but only if it can receive nothing except clear-water waste or storm sewage (OBC Div. B 7.1.1B.2.).
A sanitary drainage system must connect to a public sanitary sewer, a public combined sewer or a private sewage disposal system. Combined building drains and sewers are not allowed (OBC Div. B 7.1.2.1.).
A water distribution system connects to a public main, drinking water system or potable private water supply. Treated greywater or storm sewage may supply water closets, urinals, sub-surface irrigation or trap priming (OBC Div. B 7.1.2.3.).
Private sewers are designed and installed to MOE PIBS 6879, "Design Guidelines for Sewage Works", and private water supply pipes to PIBS 6881e (OBC Div. B 7.1.2.5.).

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Materials and protection of underground piping

Topic	Rule
Corrosive conditions	use only materials suited to excessively corrosive soil, water or wastes (OBC Div. B 7.2.1.1.)
Plastic pipe underground	must meet one of the listed CSA or ASTM standards, and (other than the two pressure pipe standards) have a stiffness of at least 320 kPa (OBC Div. B 7.2.5.9.)
Backfill over pipe	carefully placed and tamped to 300 mm over the top of the pipe, free of stones, boulders, cinders and frozen earth (OBC Div. B 7.3.5.1.)
Freezing	piping that may be exposed to freezing must be protected (OBC Div. B 7.3.5.3.)

Spatial separation from the water service

This is the Part 7 rule installers get asked about most (OBC Div. B 7.3.5.6.):

A buried water service pipe must be at least 2,440 mm horizontally from the building drain, building sewer and any private sewage disposal system, with undisturbed or compacted earth between.
Exceptions let the water service come closer to the building drain or sewer (at least 500 mm above it on a shelf, a single run with no joints, or a sewer pressure tested at 345 kPa).
If the water service is less than 15 m from a private sewage disposal system, it must be a single run of pipe with no joints or fittings between the street line or source and the inside face of the building.

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Macerating toilets, sewage treatment, interceptors and subsoil drains

A macerating toilet system is allowed only where no gravity connection is available, and only per the manufacturer's instructions (OBC Div. B 7.4.3.5.).
If a fixture discharges waste that could damage the drainage system or a sewage system, the waste must be treated before it enters the drainage system (OBC Div. B 7.4.4.1.).
Fixtures in food areas that discharge fats, oils or grease go through a grease interceptor, except in suites of residential occupancy. Service stations and repair garages need an oil interceptor. Sand and grit need their own interceptor (OBC Div. B 7.4.4.3.). Part 8 adds that restaurant kitchen waste may go to a leaching bed only after an operating grease interceptor (Chapter 5).
Foundation drains and subsoil drainage pipes do not connect to a sanitary drainage system unless no storm system is available or soil conditions prevent draining to a culvert or dry well. A permitted connection is made upstream of a trap with a cleanout, or to a trapped sump (OBC Div. B 7.4.5.3.). For a septic system, keeping clear water out is vital.

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Sumps or tanks and cleanouts

Sentences (1) to (8) of OBC Div. B 7.4.6.3. are on the syllabus:

Only piping too low to drain by gravity goes to a sump.
A sump receiving sanitary sewage is water-tight, air-tight and vented.
A pump or ejector lifts the contents to the building drain or sewer. If it is not automatic, the sump holds at least a 24 hour accumulation.
The discharge pipe has a union, a backwater valve and a shut-off valve, in that order in the direction of flow.

Cleanouts (OBC Div. B 7.4.7.1., 7.4.7.2., 7.4.7.4.), syllabus sentences only:

The drainage system must have cleanouts that allow cleaning of the entire system.
A building sewer may not change direction or slope between cleanouts, except that pipes of NPS 6 or less may change by not more than 5° every 3 m, or with fittings totalling not more than 45°.
The building drain needs a cleanout of NPS 4 or larger as close as practical to where it leaves the building.
One-way cleanouts must allow rodding in the direction of flow. Changes of direction between a cleanout fitting and the pipe it serves use 45° bends.

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Slope and fixture hydraulic loads

Drainage pipe of NPS 3 or less slopes at least 1 in 50. Force mains are exempt. Where 1 in 50 is impossible, a lesser slope is allowed if it gives gravity flow of at least 0.6 m/s (OBC Div. B 7.4.8.1.).

Table 7.4.9.3. (Table) gives each fixture's minimum outlet size and its hydraulic load in fixture units. Read across the fixture's row: the last column is the fixture-unit value. A fixture listed in the table takes that value; one that is not listed takes a value based on its trap size from Table 7.4.10.2. (OBC Div. B 7.4.10.2.).

Worked example: fixture units for a cottage greywater pit

A cottage with pressurized water sends a kitchen sink and a bathtub to a Class 2 greywater system. Table 7.4.9.3. gives a domestic sink 1½ fixture units and a bathtub 1½. Total 3 fixture units. Part 8 allows 200 L per fixture unit with pressurized water (OBC Div. B 8.4.1.2.), so the design flow is 600 L/day, under the 1,000 L/day Class 2 limit.

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Common traps

The 2,440 mm separation is horizontal and measured through undisturbed or compacted earth.
The 15 m single-run rule is about the private sewage disposal system, not the building sewer.
The pump discharge order is union, backwater valve, shut-off valve.
24 hour sump capacity applies only when the pump is not automatic.
A domestic dishwasher has no hydraulic load when connected to a garbage grinder or domestic sink.

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.

Chapter at a glance: the key idea in each section
Section	Key idea
Slope and fixture hydraulic loads	Drainage pipe of NPS 3 or less slopes at least 1 in 50. Force mains are exempt.

Slope and fixture hydraulic loads
Drainage pipe of NPS 3 or less slopes at least 1 in 50. Force mains are exempt.

Usual exam traps

The 2,440 mm separation is horizontal and measured through undisturbed or compacted earth.
The 15 m single-run rule is about the private sewage disposal system, not the building sewer.
The pump discharge order is union, backwater valve, shut-off valve.
24 hour sump capacity applies only when the pump is not automatic.
A domestic dishwasher has no hydraulic load when connected to a garbage grinder or domestic sink.

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Questions on Plumbing connections to sewage systems (Part 7), in the exam format, every answer explained and cited to its article. Sign in to start; a free account gets the free questions.

Practice this chapter On-site Sewage Systems calculations

Code cited in this chapter

Based on the official 2024 Building Code Compendium on ontario.ca.

OBC Div. B 7.1.1B.2. Floor Drains
(1)Where gravity drainage to a sanitary drainage system is possible, a floor drain shall be installed in a basement forming part of a dwelling unit.
(2)Where gravity drainage to a sanitary drainage system is not possible, the floor drain required by Sentence (1) may be connected to a storm drainage system, dry well or drainage ditch provided it is located where it can receive only clear-water waste or storm sewage.
(3)A floor drain shall be provided in a public laundry room, garbage room, incinerator room, boiler or heating room that is not located within a dwelling unit.
Open OBC Div. B 7.1.1B.2. in the code viewer
OBC Div. B 7.1.2.1. Sanitary Drainage Systems
(1)Except as provided in Section 7.7., sanitary drainage systems shall be connected to a public sanitary sewer, a public combined sewer or a private sewage disposal system.
(2)A combined building drain or a combined building sewer shall not be installed. (See Note A-7.1.2.1.(2))
Open OBC Div. B 7.1.2.1. in the code viewer
OBC Div. B 7.1.2.3. Water Distribution Systems
(1)Except as provided in Section 7.7. and Sentences (2) and (3), water distribution systems shall be connected to a public water main, drinking water system or a potable private water supply system.
(2)Storm sewage or greywater that is free of solids and treated to conform to Article 7.7.4.1. is permitted to be used as a water supply for
(a)water closets,
(b)urinals,
(c)sub-surface irrigation, or
(d)the priming of traps.
(3)Rainwater that is free of solids and treated to conform to Article 7.7.4.1. is permitted to be used as a water supply for
(a)clothes washers,
(b)laundry trays,
(c)mop sinks,
(d)bedpan washers,
(e)water closets,
(f)urinals,
(g)hose bibbs,
(h)sub-surface irrigation, or
(i)the priming of traps.
(4)Piping conveying the non-potable water described in Sentence (2) shall be installed in conformance with Section 7.7.
Open OBC Div. B 7.1.2.3. in the code viewer
OBC Div. B 7.1.2.5. Private Sewers and Private Water Supply
(1)Private water supply pipes shall be designed and installed according to MOE PIBS 6881e, "Design Guidelines for Drinking-Water Systems".
(2)Private sewers shall be designed and installed according to MOE PIBS 6879, "Design Guidelines for Sewage Works".
Open OBC Div. B 7.1.2.5. in the code viewer
OBC Div. B 7.2.1.1. Exposure of Materials
(1)Where unusual conditions exist such as excessively corrosive soil or water, only materials suited for use in such locations shall be used.
(2)Materials and equipment used in a drainage system where excessively corrosive wastes are present shall be suitable for the purpose.
Open OBC Div. B 7.2.1.1. in the code viewer
OBC Div. B 7.2.5.9. Plastic Pipe, Fittings and Solvent Cement Used Underground
(See Note A-7.2.5.9. to 7.2.5.11.)
(1)Plastic pipe, fittings and solvent cement used underground outside a building or under a building in a drainage system shall conform to
(a)ASTM F628, "Standard Specification for Acrylonitrile-Butadiene-Styrene (ABS) Schedule 40 Plastic Drain, Waste, and Vent Pipe With a Cellular Core,"
(b)CSA B181.1, "Acrylonitrile-butadiene-styrene (ABS) drain, waste, and vent pipe and pipe fittings,"
(c)CSA B181.2, "Polyvinylchloride (PVC) and chlorinated polyvinylchloride (CPVC) drain, waste, and vent pipe and pipe fittings,"
(d)CSA B182.1, "Plastic drain and sewer pipe and pipe fittings,"
(e)CSA B182.2, "PSM type polyvinylchloride (PVC) sewer pipe and fittings,"
(f)CSA B182.4, "Profile polyvinylchloride (PVC) sewer pipe and fittings,"
(g)CSA B182.6, "Profile polyethylene (PE) sewer pipe and fittings for leak-proof sewer applications," or
(h)CSA B182.8, "Profile polyethylene (PE) storm sewer and drainage pipe and fittings," for Type 1 joints and non-perforated pipes,"
(i)CSA B137.2, "Polyvinylchloride (PVC) injection-moulded gasketed fittings for pressure applications", or
(j)CSA B137.3, "Rigid polyvinylchloride (PVC) pipe and fittings for pressure applications".
(2)Except as permitted in Clauses (i) and (j), plastic pipe used as described in Sentence (1) shall have a stiffness equal or greater than 320 kPa.
Open OBC Div. B 7.2.5.9. in the code viewer
OBC Div. B 7.3.5.1. Protection of Piping
(1)Where piping is installed underground, the backfill shall be carefully placed and tamped to a height of 300 mm over the top of the pipe and shall be free of stones, boulders, cinders and frozen earth. (See Note A-7.3.5.1.(1))
Open OBC Div. B 7.3.5.1. in the code viewer
OBC Div. B 7.3.5.3. Protection Against Freezing
(1)Where piping may be exposed to freezing conditions, it shall be protected from the effects of freezing. (See Note A-7.3.5.3.(1))
Open OBC Div. B 7.3.5.3. in the code viewer

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OBC Div. B 7.3.5.6. Spatial Separation
(1)Except as permitted in Sentences (2) and (3), a buried water service pipe shall be separated from the building drain, building sewer and a private sewage disposal system, by not less than 2,440 mm measured horizontally, of undisturbed or compacted earth.
(2)The water service pipe may be closer than 2,440 mm or be placed in the same trench with the building drain or building sewer if,
(a)the following conditions are met:
(i)the bottom of the water service pipe at all points is at least 500 mm above the top of the building drain or building sewer, and
(ii)when in a common trench with the building drain or building sewer, the water service pipe is placed on a shelf at one side of the common trench,
(b)the water service pipe is constructed of a single run of pipe with no joints or fittings between the street line or source of supply on the property and the inside face of the building, or
(c)the building drain or building sewer is constructed of piping which is pressure tested in accordance with Subsection 7.3.7. at 345 kPa.
(3)A buried water service pipe may pass under a building drain or building sewer if,
(a)a vertical separation of not less than 500 mm is provided between the invert of the building drain or building sewer and the crown of the water service pipe,
(b)adequate structural support is provided for the building drain or building sewer to prevent excessive deflection of joints and settling, and
(c)the length of the water service pipe is located so that there are no joints within 2,440 mm measured horizontally from the intersection with the building drain or building sewer.
(4)A buried water service pipe shall be constructed of a single run of pipe with no joints or fittings between the street line or source of supply on the property and the inside face of the building if the water service pipe is less than 15 m from,
(a)a private sewage disposal system, or
(b)a source of pollution other than a private sewage disposal system.
Open OBC Div. B 7.3.5.6. in the code viewer
OBC Div. B 7.4.3.5. Macerating Toilet System
(1)A maceration toilet system shall only be installed
(a)where no connection to a gravity sanitary drainage system is available, and
(b)in accordance with the manufacturer's instructions.
Open OBC Div. B 7.4.3.5. in the code viewer
OBC Div. B 7.4.4.1. Sewage Treatment
(1)Where a fixture or equipment discharges sewage or waste that may damage or impair the sanitary drainage system or the functioning of a sanitary sewage works or sanitary sewage system, provision shall be made for treatment of the sewage or waste before it is discharged to the sanitary drainage system.
Open OBC Div. B 7.4.4.1. in the code viewer
OBC Div. B 7.4.4.3. Interceptors
(1)Except for suites of residential occupancy, where a fixture discharges sewage that includes fats, oils or grease and is located in an area where food is cooked, processed or prepared, it shall discharge through a grease interceptor. (See Note A-7.4.4.3.(1))
(2)Except as provided in Sentence (3), oil interceptors shall be provided as follows:
(a)service stations, repair shops and garages or any establishment where motor vehicles are repaired, lubricated or maintained shall be provided with an oil interceptor, and
(b)establishments which use oily or flammable liquids or have such wastes as a result of an industrial process shall be provided with an engineered oil interceptor.
(2.1)Oil interceptors are not required for a drain in a hydraulic elevator pit, parking lot, car wash or a garage used exclusively as a motor vehicle parking area.
(3)Where a fixture discharges sand, grit or similar materials, an interceptor designed for the purpose of trapping such discharges shall be installed.
(4)Interceptors shall have sufficient capacity to perform the service for which it is provided.
(5)An on-site constructed interceptor shall be constructed to the requirements of a manufactured interceptor.
(6)A grease interceptor shall be located as close as possible to the fixture or fixtures it serves.
(7)The flow rate through a grease interceptor shall not exceed its rated capacity and the flow rate shall be determined using the following:
Q = (∑_1^N(0.75V/DDT)) + PD
where:
Q is the flow rate to a grease interceptor in L/s.
V is the volume of the fixture in L.
DDT is the drain down time, 60 or 120 seconds.
PD is any pump discharge in L/s.
N is the number of fixtures to go through the interceptor.
(8)All grease and oil interceptors shall have an internal flow control and, where the head will exceed five feet, a secondary flow control shall be required.
(9)Floor drains that conform to Sentence 7.4.5.1.(3) are not required to be separately trapped and vented, and may be gang trapped when discharging through an oil interceptor.
Open OBC Div. B 7.4.4.3. in the code viewer
OBC Div. B 7.4.5.3. Connection of Subsoil Drainage Pipe to a Sanitary Drainage System
(1)Where a subsoil drainage pipe is connected to a sanitary drainage system, the connection shall be made on the upstream side of a trap with a cleanout or a trapped sump.
(2)Except as permitted in Sentence (3), no foundation drain or subsoil drainage pipe shall connect to a sanitary drainage system.
(3)Where a storm drainage system is not available or soil conditions prevent drainage to a culvert or dry well, a foundation drain or subsoil drainage pipe may connect to a sanitary drainage system.
Open OBC Div. B 7.4.5.3. in the code viewer
OBC Div. B 7.4.6.3. Sumps or Tanks
(1)Only piping that is too low to drain into a building sewer by gravity shall be drained to a sump or receiving tank.
(2)Where the sump or tank receives sanitary sewage, it shall be water- and air-tight and shall be vented.
(3)Where the sump or tank receives subsurface water from a subsoil drainage pipe, it shall be provided with a water-and air-tight cover.
(4)Equipment such as a pump or ejector that can lift the contents of the sump or tank and discharge it into the sanitary building drain or sanitary building sewer shall be installed.
(5)Where the equipment does not operate automatically, the capacity of the sump shall be sufficient to hold at least a 24 hour accumulation of liquid.
(6)Where there is a building trap, the discharge pipe from the equipment shall be connected to the sanitary building drain downstream of the trap.
(7)The discharge pipe from every pumped sump shall be equipped with a union, a backwater valve and a shut-off valve installed in that sequence in the direction of discharge.
(8)The discharge piping from a pump or ejector shall be sized for optimum flow velocities at pump design conditions.
(9)The discharge pipe from every pumped storm sewage sump shall be equipped with
(a)a union and a check valve installed in that sequence in the direction of discharge and pumped to above grade level, or
(b)a union, a check valve and a shut-off valve installed in that sequence in the direction of discharge.
Open OBC Div. B 7.4.6.3. in the code viewer
OBC Div. B 7.4.7.1. Cleanouts for Drainage Systems
(1)Sanitary drainage systems and storm drainage systems shall be provided with cleanouts that will permit cleaning of the entire system. (See Note A-7.4.7.1.(1))
(2)A cleanout fitting shall be provided on the upstream side and directly over every running trap.
(3)Interior leaders shall be provided with a cleanout fitting at the bottom of the leader or not more than 1 m upstream from the bottom of the leader.
(4)Where a cleanout is required on a building sewer of NPS 8 or larger, it shall be a manhole.
(5)A building sewer shall not change direction or slope between the building and public sewer or between cleanouts, except that pipes not more than NPS 6 may change direction
(a)by not more than 5° every 3 m, or
(b)by the use of fittings with a cumulative change in direction of not more than 45°.
(6)Building drains shall be provided with a cleanout fitting of NPS 4 or larger that is located as close as practical to the place where the building drain leaves the building. (See Note A-7.4.7.1.(6))
(7)Stacks shall be provided with a cleanout fitting
(a)at the bottom of the stack,
(b)not more than 3 m upstream of the bottom of the stack, or
(c)on a Y fitting connecting the stack to the building drain or branch.
(8)A cleanout shall be provided to permit the cleaning of the piping immediately downstream of an interceptor.
(9)Every indirect drainage pipe carrying waste from a food receptacle shall have a cleanout access at every change of direction of more than 45°.
(10)A cleanout shall be installed on a trap arm serving a kitchen sink as close as practical to the trap outlet and shall be readily accessible.
Open OBC Div. B 7.4.7.1. in the code viewer
OBC Div. B 7.4.7.2. Size and Spacing of Cleanouts
(1)Except as provided in Sentences (2), (3) and 7.4.7.1.(6), the nominal pipe size and spacing of cleanouts in nominally horizontal pipes of a drainage system shall conform to Table 7.4.7.2.
(2)The spacing between manholes serving a building sewer
(a)of NPS 24 or less shall not exceed 90 m, and
(b)over NPS 24 shall not exceed 150 m.
(3)The developed length of a building sewer between the building and the first manhole to which the building sewer connects shall not exceed 75 m.
(4)Where a building sewer connects to another building sewer other than by a manhole, the developed length between the building and the building sewer to which it connects shall not exceed 30 m.
(5)Cleanouts that allow rodding in one direction only shall be installed to permit rodding in the direction of flow.
(6)Manholes shall be located at all junctions and all changes in grade, size or alignment (except for curvilinear alignment) on a sanitary building sewer that is NPS 8 or larger.
(7)Manholes shall be located at changes of grade, size or alignment (except for curvilinear alignment) on a storm building sewer or exterior storm drainage pipe that is NPS 8 or larger.
Open OBC Div. B 7.4.7.2. in the code viewer
OBC Div. B 7.4.7.4. Location of Cleanouts
(1)Cleanouts and access covers shall be located so that their openings are readily accessible for drain cleaning purposes.
(2)A cleanout shall not be
(a)located in a floor assembly in a manner that may constitute a hazard, and
(b)used as a floor drain.
(3)Reserved.
(4)Each change of direction of the piping between a cleanout fitting and the drainage piping or vent piping that it serves shall be accomplished by using 45° bends.
(4.1)A cleanout shall be provided to serve vertical drainage piping from a wall hung urinal and shall extend above the flood level rim of the fixture.
(5)Cleanouts serving fixture drains in healthcare facilities, mortuaries, laboratories and similar occupancies, where contamination by hazardous waste is likely, shall be located a minimum of 150 mm above the flood level rim of the fixture.
Open OBC Div. B 7.4.7.4. in the code viewer
OBC Div. B 7.4.8.1. Minimum Slope
(1)Except as provided in Sentences (2) and (3) and Articles 7.4.10.8. and 7.4.10.9., drainage pipes that are NPS 3 or less shall have a downward slope in the direction of flow of at least 1 in 50. (See Note A-7.4.8.1.(1))
(2)Sentence (1) does not apply to a force main.
(3)Where it is not possible to comply with Sentence (1), a lesser slope may be used if it will produce a gravity flow of not less than 0.6 m per second.
Open OBC Div. B 7.4.8.1. in the code viewer
OBC Div. B Table 7.4.9.3. Minimum Permitted Size of Fixture Outlet Pipe and Hydraulic Loads for Fixtures[1]
Table 7.4.9.3. — Minimum Permitted Size of Fixture Outlet Pipe and Hydraulic Loads for Fixtures[1] Forming Part of Sentences 7.4.9.3.(1) and 7.4.10.2.(1) Fixture | Minimum Nominal Pipe Size of Fixture Outlet Pipe, NPS | Hydraulic Load, fixture units Autopsy table | 1½ | 2 Bathroom group (a) with flush tank | N/A | 6 Bathroom group (b) with direct flush valve | N/A | 8 Bathtub (with or without shower) | 1½ | 1½ Bath: foot, sitz or slab | 1½ | 1½ Beer cabinet | 1½ | 1½ Bidet | 1¼ | 1 Chinese range | 1½ | 3 Clothes washer (a) domestic[1] | N/A | 1½ with NPS 2 trap Clothes washer (b) commercial | N/A | 2 with NPS 2 trap Cup sinks | 1¼ | ½ Dental unit or cuspidor | 1¼ | 1 Dishwasher (a) domestic type | 1½ | 1 (no load when connected to garbage grinder or domestic sink) Dishwasher (b) commercial type | 2 | 3 Drinking fountain | 1¼ | ½ Fish tank or tray | 1½ | 1½ Floor drain[2] | 2 | 2 with NPS 2 trap 3 with NPS 3 trap Garbage grinder, commercial type | 2 | 3 Icebox | 1¼ | 1 Laundry tray (a) single or double units or 2 single units with common trap | 1½ | 1½ Laundry tray (b) compartments | 1½ | 2 Lavatory (a) barber or beauty parlor | 1½ | 1½ Lavatory (b) dental | 1¼ | 1 Lavatory (c) domestic type single, or 2 single with common trap | 1¼ | 1 with NPS 1¼ trap 1½ with NPS 1½ trap Lavatory (d) multiple or industrial type | 1½ | According to Table 7.4.10.2. Macerating toilet system | ¾ | 4 Potato peeler | 2 | 3 Shower drain Total volume of discharge from all shower heads and body sprays: (a) from 1 head | 1½ | 1½ Shower drain Total volume of discharge from all shower heads and body sprays: (b) from 2 or 3 heads | 2 | 3 Shower drain Total volume of discharge from all shower heads and body sprays: (c) from 4 to 6 heads | 3 | 6 Sink (a) domestic and other small types with or without garbage grinders, single, double or 2 single with a common trap | 1½ | 1½ Sink (b) other sinks | 1½ | 1½ with NPS 1½ trap 2 with NPS 2 trap 3 with NPS 3 trap Urinal (a) pedestal, siphon jet or blowout type | 2 | 4 Urinal (b) stall, washout type | 2 | 2 Urinal (c) wall (i) washout type | 1½ | 1½ Urinal (c) wall (ii) other types | 2 | 3 Water closet (a) with flush tank | 3 | 4 Water closet (b) with direct flush valve | 3 | 6 Notes to Table 7.4.9.3.: (1) See Note A-Table 7.4.9.3. (2) No hydraulic load for emergency floor drains.
Open OBC Div. B Table 7.4.9.3. in the code viewer
OBC Div. B 7.4.10.2. Hydraulic Loads for Fixtures
(1)The hydraulic load from a fixture that is listed in Table 7.4.9.3. is the number of fixture units set forth in the Table.
(2)Except as provided in Sentence (1), the hydraulic load from a fixture that is not listed in Table 7.4.9.3. is the number of fixture units set forth in Table 7.4.10.2. for the nominal pipe size of the trap that serves the fixture.
Open OBC Div. B 7.4.10.2. in the code viewer
OBC Div. B 8.4.1.2. Application
(1)A Class 2 sewage system shall be designed only for the treatment and disposal of greywater.
(2)The total daily design flow for a Class 2 sewage system shall be calculated based on the fixtures discharging to the system as follows:
(a)200 L per fixture unit where there is a supply of pressurized water, and
(b)125 L per fixture unit where there is no supply of pressurized water.
Open OBC Div. B 8.4.1.2. in the code viewer