STACK VENTS, VENT STACKS, AND RELIEF VENTS

Stack vents, vent stacks, and relief vents require more information for sizing. Specifically, you must know the fixture-unit load on a drain before you can determine vent sizing and developed lengths. Once you have calculated the fixture units, a sizing table can be used to give you your sizing information. The table shown in Figure 5.31 is the type of table that would be used to de­fine the requirements of stack vents, vent stacks, and relief vents. Like the other tables, this one is self-explanatory. To prove this, size the diameter and maximum length of a vent stack that will serve 20 fixture units with a drain di­ameter of two inches. Assume that you want your vent pipe to have a diame­ter of one and a half inches. The answer is that your vent size is okay, as long as you don’t extend it more than 50 feet. If you need more distance, increase the size of the vent to a 2-inch diameter and feel free to run the vent up to 150 feet. The table is easy to use, but you must be able to calculate the load of fixture units. How will you do that? I’ll show you.

Подпись:Most codebooks will provide you with some form or a chart or table that identifies fixture-units for drainage piping. A table like the one in Figure 5.32 is quite helpful. By looking at such a table, you can quickly determine the load, in terms of fixture units, that an individual fixture puts on a drain. For example, a bidet carries a fixture-unit rat­ing of 2. A drinking fountain is rated for one half of a fixture unit. A residential wa­ter closet is worth 4 fixture units. By using this type of table to assign fixture-unit rat­ings to all fixtures being served by a drain, you can then arrive at a number to use with the vent-sizing table. For fixtures that are not listed, you can use a generic table, like the one in Figure 5.33, to assign ratings for fixture units.

‘О

оо

 

Подпись: PLUMBER’S AND PIPE FITTER’S CALCULATIONS MANUAL
STACK VENTS, VENT STACKS, AND RELIEF VENTS

FIGURE 5.30 ■ Individual and branch vent sizing table for horizontal soil and waste branches. [Courtesy of Standard Plumbing Code)

Size of soil or

Diameter of vent required (in)

(in)

connected

lVi

1У2

2

2У2

3

4

5

6

8

V/i

2

30

1V5>

8

50

150

1У2

10

30

100

2

12

30

75

200

2

20

26

50

150

2’/2

42

30

100

300

3

10

30

100

200

600

3

30

60

200

500

3

60

50

80

400

4

100

35

100

260

1000

4

200

30

90

250

900

4

500

20

70

180

700

5

200

35

80

350

1000

5

500

30

70

300

900

5

1100

20

50

200

700

6

350

_

_

25

50

200

400

1300

6

620

15

30

125

300

1100

6

960

—•

24

100

250

1000

6

1900

20

70

200

700

8

600

50

150

500

1300

8

1400

_

_

_

__

_

40

100

400

1200

8

2200

30

80

350

1100

8

3600

25

60

250

800

10

1000

75

125

1000

10

2500

50

100

500

10

3800

_

_

_

30

80

350

10

5600

25

60

250

1 in = 25.4 mm 1 ft = 0.3048 m

Подпись: VENT SYSYEM CALCULATIONSFIGURE 5.31 ■ Maximum length of stack vents, vent stacks, and relief vents. (Courtesy of Standard Plumbing Code)

‘O

SO

 

Fixture type

Fixture-unit value as load factors

Minimum size of trap (in)

Bathroom group consisting of water closet, lavatory, and bathtub or shower

6

Bathtub1 (with or without overhead shower) or whirlpool attachments

2

lVz

Bidet

2

Nominal 1У2

Combination sink and tray

3

T/2

Combination sink and tray with food disposal unit

4

Separate traps ІУ2

Dental unit or cuspidor

1

1У4

Dental lavatory

1

1У4

Drinking fountain

‘/2

1

Dishwashing machine2 domestic.

2

1У2

Floor drains5

1

2

Kitchen sink, domestic

2

1У2

Kitchen sink, domestic with food waste grinder and/or dishwasher

3

1У2

Lavatory4

1

Small P. O. l’/4

Lavatory4

2

Large P. O. 1У2

Lavatory, barber, beauty parlor

2

ІУ2

Lavatory, surgeon’s

2

ІУ2

FIGURE 5.32 ■ Fixture units per fixture or group. (Courtesy of Standard Plumbing Code)

Updated: 15 ноября, 2015 — 3:58 пп