Roofs and paved areas, yards, courts and courtyards shall be drained
into a storm sewer system or a combined sewer system where such systems are
available.
Stormwater shall not be drained into sewers intended for sanitary sewage
only.
Leaders and storm drains, when connected to a combined sewer, shall
be effectively trapped, except roof leaders and conductors, where the roof
or gutter opening is located not less than 12 feet from a door, window or
ventilating opening. When the sanitary and stormwater drainage are combined
within the building, one trap on the main storm drain of the building may
serve. Traps shall be set below the frost line or on the inside of the building.
Where subsoil drains for drainage are placed under cellar floors, the
seepage shall be piped to a silt pit or sand trap by field tile. The silt
pit or sand trap shall discharge into a four-inch running trap with two cleanouts
and, in localities where the administrative authority thinks it advisable,
it shall have a backwater valve. Subsoil drains may discharge into a properly
trapped area drain or sump.
Subsoil drains below the sewer level and cellar floor drains or drips
from machinery shall be discharged into an independent sump or receiving tank,
the contents of which shall be automatically lifted and discharged into the
drainage system above the cellar through some properly trapped fixture or
drain. The discharge of automatic systems shall be protected against back
pressure.
When subsoil catch basins are installed below the sewer level, automatic
electric ejectors provided with a ball float or equivalent shall be used.
Such ejectors or any device raising subsoil water shall discharge into a water-supplied,
trapped and vented sink or into a stormwater drain.
Leaders, when placed within a building, shall be of cast iron, galvanized
steel, galvanized wrought iron, brass, copper or lead.
When outside leaders are of sheet metal and connected with a building
storm drain or storm sewer, they shall be connected to a cast-iron drain extending
above the finished grade.
Building storm drains, when underground, shall be of extra-heavy cast-iron,
brass or copper pipe.
The building storm sewer, from the building to the property line, shall
be of cast-iron, Orangeburg or vitrified clay pipe.
When an existing sheet metal leader pipe within the walls of any building
becomes defective, such leader shall be replaced by one which conforms to
this chapter.
The size of a vertical leader shall be based upon the maximum projected
roof area as given in the following table:
|
Nominal Leader Size Equivalent Diameter
(inches)
|
Maximum Projected Roof Area
(square inches)
|
|---|---|
|
2
|
500
|
|
2Â 1/2
|
900
|
|
3
|
1,500
|
|
4
|
3,100
|
|
5
|
5,500
|
|
6
|
9,000
|
|
8
|
19,000
|
|
10
|
35,000
|
|
12
|
56,000
|
The minimum size of building storm sewer, building storm drain or any
of its branches, having a fall of 1/2 inch or less per foot, shall be
based upon the maximum roof area to be handled, according to the following
table:
|
Maximum Drained Area
(square feet)
| |||
|---|---|---|---|
|
Diameter of Pipe
(inches)
|
1/8-Inch Fall Per Foot
|
 1/4-Inch Fall Per Foot
|
1/2-Inch Fall Per Foot
|
|
2
|
500
| ||
|
2Â 1/2
|
900
| ||
|
3
|
700
|
1,000
|
1,500
|
|
4
|
1,500
|
2,150
|
3,100
|
|
5
|
2,700
|
3,800
|
5,500
|
|
6
|
4,300
|
6,100
|
9,000
|
|
8
|
9,600
|
13,000
|
19,000
|
|
10
|
16,500
|
24,000
|
35,000
|
|
12
|
27,000
|
40,000
|
56,000
|
The sanitary and storm drainage system of a building shall be entirely
separate, except that where a combined sewer is available, the building drain
and the building storm drain may be connected to a combined building drain
and building storm drain or to a combined sewer downstream and preferably
at least 10 feet from any stack connection.
The size of building drains and building storm drains up to the point
of combining into one system shall be as required for separate storm and sanitary
systems.
To determine the size of a combined drain or sewer, the connected fixture units shall first be converted to square feet of roof area by the use of the following table in § 221-291 of this article. The number of square feet of roof area served by the combined drain or sewer and the pipe size shall be determined by using the table in § 221-287 of this article, except that the combined sanitary and building storm sewers shall be at least six inches in size.
The roof-area equivalents for fixture units on combined drains and sewers
shall be as follows:
|
Fixture Units
|
Roof Area
(square feet)
|
Fixture Units
|
Roof Area
(square feet)
|
|---|---|---|---|
|
10
|
325
|
600
|
4,525
|
|
15
|
400
|
700
|
5,150
|
|
20
|
450
|
800
|
5,725
|
|
25
|
500
|
900
|
6,350
|
|
30
|
525
|
1,000
|
7,525
|
|
35
|
550
|
1,200
|
8,725
|
|
40
|
575
|
1,400
|
9,800
|
|
45
|
625
|
1,600
|
10,000
|
|
50
|
675
|
1,800
|
11,825
|
|
60
|
725
|
2,000
|
14,000
|
|
70
|
800
|
2,500
|
16,800
|
|
80
|
850
|
3,000
|
19,000
|
|
90
|
925
|
3,500
|
21,000
|
|
100
|
1,100
|
4,000
|
23,200
|
|
125
|
1,225
|
4,500
|
25,400
|
|
150
|
1,375
|
5,000
|
28,000
|
|
175
|
1,525
|
6,000
|
31,200
|
|
200
|
1,850
|
7,000
|
34,100
|
|
250
|
2,125
|
8,000
|
36,500
|
|
300
|
2,450
|
9,000
|
40,000
|
|
350
|
2,725
|
10,000
|
46,000
|
|
400
|
3,100
|
12,000
|
55,000
|
|
450
|
3,325
|
15,000
|
70,200
|
|
500
|
3,950
|
20,000
|
85,000
|
