Section 3 Single Stack System -...

STUDENT NOTES CPCPSN4011A Plan, size and layout sanitary pipe work and fixtures

© 2012 TAFE NSW Section 3-1

3. Sanitary Plumbing Single Stack System On completion of this section, students should be able to: Design, install and develop bills of quantities for the Single Stack Systems for domestic, commercial and industrial premises of over SIX (6) floor levels and interpret sanitary plumbing design for the systems.

Assessment Criteria 3.1 Describe, design, install and develop bills of quantities for single stack sanitary plumbing

systems for domestic, commercial and industrial premises to meet the requirements of the Building Code of Australia, Plumbing Code of Australia and AS/NZS 3500.

3.2 Describe, design, install and develop bills of quantities for single stack modified sanitary

plumbing systems for domestic, commercial and industrial premises to meet the requirements of the Building Code of Australia, Plumbing Code of Australia and AS/NZS 3500.

Assessment Method may include

• Written assessment based on assessment criteria.

• Practical activities based on assessment criteria.

• Designs based on assessment criteria.

• Assignment based on assessment criteria



3.1 Describe, design, install and develop bills of quantities for single stack sanitary plumbing systems for domestic, commercial and industrial premises to meet the requirements of the Building Code of Australia, Plumbing Code of Australia and AS/NZS 3500.

Refer Plumbing & Drainage Guide (BRANZ) If a multi-story building can be designed within the parameters of a single stack system, then this will usually be the simplest and most economic method of providing sanitary plumbing. A single stack system: a) is generally designed around stacks of DN 100 diameter, but there are variations to this; b) is based on the principle that there is sufficient air within the system for a number of

fixtures to be connected to the stack without the need to vent individual fixture discharge pipes;

c) the load effect of fixtures connected to the stack d) the maximum number of floor levels permitted to be connected to the stack are limited e) the class of the building (Residential or Commercial) f) where relief vents and cross-vents are installed and g) the number and type of fixtures permitted to be connected at any one floor level

Principles of Operations Refer AS/NZS 3500.2 Clause 8.2.1 The single stack systems are designed on the principles that the air within the discharge pipes from fixtures, the stack and the stack vent allows the permitted type and number of fixtures to be connected to the stack without the need for individual trap vents/air admittance valves or, in the case of ranges of fixtures, venting of the common discharge pipe.



Sizing of Stacks – Residential Buildings

Refer AS/NZS 35.00.2 Clause 8.7 Stacks are sized by totalling the individual fixture unit ratings as given in Table 6.1 and considering the maximum number of floors through which the stack may pass (see Table 8.3), if the point at which the stack connects to the drain is more than 2.4 m below the lowest floor level, then that length of pipe must be counted as a floor level (refer AS/NZS 3500.2 Figure 8.3).

Sizing Single Stack Systems for Domestic or Residential Buildings Using AS/NZS3500.2 students are to complete the table below

Table 8.3 Single Stack System – Domestic or

Residential Buildings Size of stack

DN Maximum fixture unit

loading Maximum number of

consecutive floor levels

100

125

150

The maximum number and type of fixtures that are permitted to be connected at any floor level for a residential building are: Refer AS/NZS 3500.2 Clause 8.4.1

2 basins

2 baths

2 bidets

2 cloths-washing machines

2 dishwashing machines

2 kitchen sinks (double or single domestic with or without food waste disposal units)

2 laundry troughs

2 showers

2 water closet pans

2 floor waste gullies

2 bar sinks



Ground

S B

Shr Bth.

B

Shr Bth.

B

Shr Bth.

B

Shr Bth.

B

Shr Bth.

WC

WC

WC

WC

WC

Shr

Shr

Shr

Shr

ShrWC

WC

WC

WC

WC

Tr. (L)

Tr. (L)

Tr. (L)

Tr. (L)

Tr. (L)

B

B

B

B

B

S

S

FW

FW

FW

FW

FW

S

STACK VENT (SEE CLAUSE 8.6)

FW

OBLIQUE JUNCTION

OBLIQUE JUNCTION

Fig. 3.1 Single stack residential building



Sizing Single Stack Systems for Commercial or Industrial buildings

Using AS/NZS3500.2 students are to complete the table below

Table 8.4 Single Stack System – Commercial or

Industrial Buildings Size of stack

DN Maximum fixture unit

loading Maximum number of

consecutive floor levels 100

125

150

The maximum number and types of fixtures that are permitted to be connected at any floor level for a commercial or industrial building are: Refer AS/NZS 3500.2 Clause 8.4.2

5 basins

1 cleaner’s sink

1 drinking fountain

1 sink

5 wall-hung urinals

5 water closet pans

2 showers

1 x 3 m slab type urinal

2 bar sinks

Note:

• No additional or alternative fixtures shall be connected except tundishes receiving minor discharges.

• At any one floor level, the maximum discharge from all floor waste gullies shall not exceed five basins, one drinking fountain, one cleaner’s sink and two showers (see Note 3 to Table 6.1).

• Within commercial and industrial buildings the following fixtures may be connected in a range of fixtures as listed below and shown in Fig. 8.2:

i) 5 basins;

ii) 5 wall-hung urinals; and

iii) 5 water closet pans.

• The conditions for the connection method will be covered later in this learning outcome.

• If your design does not fall within the conditions mentioned, then you would need to consider a Fully Vented Modified System.



Fig. 3.2 Single stack commercial or industrial building



Connection of Fixture Discharge Pipes In domestic or residential buildings, fixtures shall be connected to the stack individually or through floor waste gullies. In commercial or industrial buildings, fixtures may be connected to the stack individually, through floor waste gullies or in a range of the same type of fixtures.

Unequal Oblique Stack Junction

Refer AS/NZS 3500.2. As well as the above methods of connections, two waste fixture discharge pipes, including discharge pipes from floor waste gullies may be connected at the same level within 1 m of the stack, by means of an oblique junction if:

a) the angle between the two fixture discharge pipes shall be not greater than 45°. b) the outlet of the junction is one size larger than the largest fixture pipe except in the case

of a floor waste gully that does not receive the discharge from a fixture; and. c) the section of pipe downstream of the 45° junction is included as part of the permitted

maximum length of the fixture discharge pipe.

STACK

1 m max.

FIXTURE DISCHARGE PIPE


45° max.

45° JUNCTION ONE PIPE SIZELARGER THAN LARGEST


Fig. 3.3 Unequal oblique stack junction



Length of Fixture Discharge Pipes

Length and gradients of unvented fixture discharge pipes Using AS/NZS3500.2 students are to complete the table below Fixture type Max. length

(m) Permitted grade

% Waste fixture

WC pan DN 100

WC pan DN 80

Urinal DN 50 to 80

Note:

• If the length of fixture discharge pipes exceeds that as outlined above and within Appendix D, then a Trap Vent or Air Admittance Valve must be fitted.

• As stated at the start of this learning outcome, a single stack system is designed on the principle that the air within the discharge pipes, the stack and stack vent allows the type and number of fixtures to be connected without the need for extra ventilation.

• Extra consideration has to be given to the fixture discharge pipes apart from size, length and grade; such as the number of bends.



Bends in fixture discharge pipes Refer AS/NZS 3500.2.

Basins and Bidets Shall have not more than two bends in the horizontal plane and two bends in the vertical plane.

Other Fixtures Shall have not more than two bends in the horizontal plane and three bends in the vertical plane. Note:

• Bends 45° or less are not considered as a change of direction or grade.

• If a design needed more than the allowed bends as stated above, the discharge pipe would need venting either via a trap vent or air admittance valve.

Refer Plumbing and Drainage Guide (BRANZ)

Fig. 3.4 Connection of basins and bidets to a branch pipe or stack

Developed length of discharge pipe must not exceed 2.5 m

Basin or bidet

DN 40 min. trap Stack or graded pipe

1st vertical bend

Total drop of discharge pipe must not exceed 1.5 m

2nd

vertical bend

1st horizontal

bend

2nd

horizontal bend

for basins and bidets the max. bends allowed are:

• two in the horizontal plane

• two in the vertical plane




Fig. 3.5 Connection of fixtures other than basins and bidets to a branch pipe or stack

Trap Vents and Air Admittance Valves on over distance discharge pipes. If the fixture discharge pipe is over distance, a vent or air admittance valve is required. This must be connected in accordance with the requirements set out in AS/NZS 3500.2. The size of the vent is dependant on the size of the fixture trap, using AS/NZS3500.2 complete the table below Using AS/NZS3500.2 students are to complete the table below

TABLE 7.3 MINIMUM SIZE OF TRAP VENTS

Size of fixture trap DN

Size of trap vent DN

40

>50 >100

32

40



Show on the diagrams below the permitted points of connection for the trap vent and the maximum and minimum distance from the trap that the vent should be located

1.5 m max.

A

B

Connect vent/AAV within either Section A or B

P-trap or S-trap

Connect vent/AAVwithin this length

75 mm no connections

permitted within

this distance

600 mm for basins/bidets

1.5 m for other fixtures75 mm

No connectionspermitted withinthis distance

300 mm min.

No connectionspermitted withinthis distance

FIG. 3.6 Connection of vents/AAV to graded discharge pipes Using AS/NZS3500.2 students are to complete the table below

TABLE 6.6 MINIMUM DETERMINED AIRFLOW CAPACITY OF AIR ADMITTANCE VALVE WHEN USED

AS A TRAP, GROUP VENT OR BRANCH DRAIN VENT Fixture unit loading of

discharge pipe Minimum airflow capacity

of AAV, L/s 6 9

10

12 18 24

30 36 42

48 54 60



Installation of Trap Vents. Trap vents and air admittance valves are installed in one of the following four ways. Draw the approved installation methods. Refer AS/NZS 3500.2.

FIXTURE TRAP

100 mm min.

TRAP VENT OR AAV

(a)

GRADE 1.25% min.

100 mm min.

TRAP VENT OR AAV

(b)

100 mm min.

GRADE 1.25% min

TRAP VENT OR AAV

(c)

TRAP VENT

GRADE 1.25% min.

VENT TO RISE ABOVE

RIM OF FIXTURE

100 mm min.

ALTERATIVEUSE AAV

(d)

Fig. 3.7 vent installation.

Venting of Stack

Refer AS/NZS 3500.2. The stack shall continue upwards to the vent cowl undiminished in size. Stacks that extend not more than three floor levels with a maximum loading of 30 fixture units may have the vent reduced to DN 50.



Three waste fixtures only basins, showers or kitchen sinks may be connected to this top DN 50 vertical section. Refer AS/NZS 3500.2.

Connection of ranges of fixtures This allows groups of fixtures of the same type, to be connected through a common branch pipe without the need for extra ventilation.

Basins

Refer AS/NZS 3500.2.

• The maximum number of basins shall be five The fixture discharge pipe shall be:

a) of size DN 40;

b) not longer than 1 m;

c) installed with not more than one bend; and

d) graded within the range of 2.5 to 5%. The common discharge pipe shall be:

a) not smaller than DN 50;

b) not longer than 4.5 m;

c) installed without a bend; and

d) graded within the range of 2.5 to 5%. The distance between the centre-line of adjacent traps and between the near face of the stack and the centre-line of the nearest trap shall not exceed 2 m.




Fig. 3.8 Connection of a range of basins

2m max. between basin

traps

max. of five basins in a range

common discharge pipe 4.5m max. with no bends; min. diameter DN 50

2m max. from stack to first trap

grade 2.5 to 5.00%



Water Closet Pans


• The maximum number of WC’S shall be five The fixture discharge pipe shall be:

a) not longer than 1.5 for S-trap pans and 2 m for P-trap pans;

b) installed with a maximum of two bends; and

c) graded within the range of 1.65 to 5%. The common discharge pipe shall be:

a) not smaller than DN 100;


c) installed with not more than two bends; and

d) graded within the range of 1.65 to 5%. The distance between the centre-line of adjacent traps and between the near face of the stack and the centre-line of the nearest trap shall not exceed 6 m.


Fig. 3.9 Connection of a range of WC’s p-trap

max. of five WC pans

Fixture discharge pipe 2m max. for “P” traps

combined discharge pipe

• max. of two 45° bends

• gradient 1.65 to 5.0%

• min. DN 100

• max. length 10m stack

6m max.

6m max.




Fig. 3.10 Connection of a range of WC’s s-trap

Wall-hung Urinals


• The maximum number of wall-hung urinals shall be five The fixture discharge pipe shall be:

a) of size DN 50;


c) installed with not more than one bend; and

d) graded within the range of 2.5 to 5%. The common discharge pipe shall be:

e) not smaller than DN 65;

f) not longer than 10 m;

g) installed with not more than two bends; and

h) graded within the range of 2.5 to 5%.

max. of five WC pans

1.5m max. dropper

fixture discharge pipe:


• Max. of two bends


• max. of two 45° bends


• min. pipe size DN 100

• max. length 10m

10 m max.



The distance between the centre-line of adjacent traps and between the near face of the stack and the centre-line of the nearest trap shall not exceed 2.5 m.


Fig. 3.11 Connection of a range of wall-hung urinals Note:

If waterless urinals are used they must have two fixtures connected to the discharge pipe upstream of the urinal.

Offsets in Single Stack Systems

Refer AS/NZS 3500.2

An offset may be a steep offset, made up of angles of more than 45° to the horizontal. A graded

offset, made up of an angle of less than 45° to the horizontal, with a minimum grade of 2.5% for DN 80 waste stacks and 1.65% for DN 100 or larger stacks. DN 100 stacks may be offset between the base of the stack and the highest connection as long as;

• the height of the stack must not exceed 10 floor levels;

• if laundry troughs are connected above the upper offset bend, the maximum fixture unit loading for the stack is not to exceed 50.

max. of five wall-hung urinals

1m max.

fixture discharge pipe

• min. grade 2.5 to 5.0%

• max. length 1m

• max. one bend

• min. size DN 50


• min. size DN 65

• max. length 10m

• max. of two bends





TABLE 8.9 OFFSET REQUIREMENTS

Maximum height in consecutive floor levels above the

upper offset bend

Minimum distance between upper offset bend and

connection of fixture discharge pipe

Mm

Minimum distance between lower offset

bend and connection of fixture discharge pipe

mm

Maximum fixture unit loading

5

10

10

Ground

1st

2nd

3rd

4th

STACK DN 100 min.

TO SEWER

45°Min. DISTANCE(SEE TABLE 8.9)

600 mm min.

Fig. 3.12 Typical steep connection



Steep offset below the lowest connection

Refer AS/NZS 3500.2. Where a steep offset is below the lowest connection;

• the height of the stack must not exceed 3 floor levels;

• there is a maximum number of 30 fixture units permitted through the offset;

• laundry troughs shall not be connected.

45°

To sewer

Lowest grades pipe100 mm min.(see Clause 8.9.4)

Fig. 3.13 Steep offset below lowest connection Note:

In an area where foaming is likely to occur, the minimum distance permitted at or near the offset may need to be increased.



Graded Offset

Refer AS/NZS 3500.2. A DN 100 stack may be offset between the base of the stack and the highest connection as long as;

• only one graded offset is permitted;

• with a maximum of 10 consecutive floor levels;

• with a minimum of 2 m between centre-lines of vertical sections;

• The upper vertical section must be installed in accordance with Clause 7.6.2; and

• the graded lower vertical section in accordance with Table 7.8


TABLE 7.8 MINIMUM GRADE OF OFFSET

Size of graded section DN

Min. gradient %

<80

100

125

150

225

300



600 min.

900 min.

450 min.2500 min.

WC only with DN 40 trap vent

(600 min.)

900 min.

or Air Admittance Valve

as per AS/NZS 3500.2 Clause 6.9

Stack vent (see Clause 8.6)

2 m min.

Fig. 3.14 Graded offset



3.2 Describe, design, install and develop bills of quantities for single stack modified sanitary plumbing systems for domestic, commercial and industrial premises to meet the requirements of the Building Code of Australia, Plumbing Code of Australia and AS/NZS 3500.

The single stack modified system permits stacks to receive a higher discharge loading or to be extended to serve a greater number of floor levels by introducing a relief vent and cross-vents. The cross-vents are installed between the stack and relief vent or the installation of pressure attenuators.

The introduction of a relief vent and cross-vents into the system, allows for any excess pressure variations to be alleviated. The connection of the fixture and discharge pipes is the same as that covered for the single stack system; the only difference is the addition of a relief vent and cross-vents or the use of pressure attenuators. Using AS/NZS3500.2 students are to complete the table below

TABLE 8.5 SINGLE STACK MODIFIED SYSTEM – DOMESTIC

OR RESIDENTIAL BUILDINGS

Size of stack DN

Maximum fixture unit

loading

Maximum number of


Size of relief vent and cross-

vent DN

Location of cross-vents

100

100

100

100

Alternate floors

Each floor

Alternate floors

Each floor

TABLE 8.6

SINGLE STACK MODIFIED SYSTEM – OTHER THAN RESIDENTIAL TYPE BUILDINGS

Size of stack DN

Maximum fixture unit

loading

Maximum number of


Size of relief vent and cross-

vent DN

Location of cross-vents

100

125

150

Each floor

Each floor

Each floor



Fig 3.15 Single stack modified residential building



Fig. 3.16 Single stack modified commercial or industrial building



Waste Stacks

Waste stacks may be used to pick up waste fixtures only;


TABLE 8.1 SIZE OF WASTE STACK

Size of stack DN

Maximum fixture unit loading

40

50

65

80

100

TABLE 8.7 WASTE STACKS – LOADING PERMITTED

THROUGH GRADED OFFSET Size of graded section

of offset DN

Maximum fixture unit loading permitted through the offset

40

50

65

80

100

A DN 65 waste stack may receive the discharge from kitchen sinks and laundry troughs provided;

• the stack does not exceed two floor levels measured between its base and the highest floor

level to which fixtures are connected;

• only two kitchen sinks or one kitchen sink and one laundry trough are separately connected at each floor level.



Acceptable Variations

AS/NZS 3500 Clause 8.8 lists acceptable variations to the requirements for single stack system such as:

a) A DN 80 stack up to three floors in height for domestic or residential buildings;

b) A DN 80 stack up to two floors with the top section graded; c) A DN 100 stack up to three floors with the top section graded, receiving up to 30 fixture

units; d) A DN 100 stack of one floor with the top section graded, receiving 90 fixture units; Students are encouraged to read these variation and the others listed to gain an understanding of the special conditions for their installation.



CPCPSN4011A

Plan, size and layout sanitary pipe work and fixtures

Section 3

Student Name:

Due date: ________________ Answer the following questions in the space provided ‘Quote references’. 1. Name the parts of the stack shown below as numbered.

1. STACK VENT

3. STACK

4. SINGLE STACK SYSTEM8. SINGLE STACK

MODIFIED SYSTEM

6. RELIEF VENT

7. CROSS VENT

2. FIXTURE TRAP

5. FLOOR WASTE GULLY

1) 2)

3) 4)

5) 6)

7) 8)



2. What is the principle a single stack system operates on?

3. What is the difference in design between a single stack and single stack modified

systems?

4. What is meant by the term, “Range of Fixtures”?

5. In what type of building (classification) is a range of fixtures allowed to be installed,



6. A single stack sanitary plumbing system is possibly the most common type of stack design used in “low rise” domestic buildings.

a) Explain THREE (3) benefits of this system. i) ii) iii) b) Explain TWO (2) disadvantages of the Single Stack system. i) ii)



Instructions: Complete the design below to comply with the requirements of AS/NZS 3500. 1. Draw directly onto this sheet. Using the correct colour code. 2. Provide all pipe sizes. 3. Show the number of fixture units per floor and include a total. 4. Include any venting requirements and indicate where you would locate any Air

Admittance Valve.

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