N.Y.C. Admin. Code § PC 1403: Section PC 1403: Installation

1403.1 Installation.

Absorption systems shall be installed in accordance with Sections 1403.1.1 through 1403.1.5 to provide landscape irrigation without surfacing of water.

1403.1.1 Absorption area.

The total absorption area required shall be computed from the estimated daily gray water discharge and the design-loading rate based on the percolation rate for the site. The required absorption area equals the estimated gray water discharge divided by the design-loading rate from

Table 1403.1.1

.

Table 1403.1.1 Design Loading Rate

Percolation Rate (minutes per inch)

Design Loading Factor (gallons per square foot per day)

< 1

Not suitable

1 - 5

1.20

6 - 7

1.00

8 - 10

0.90

11 - 15

0.80

16 - 20

0.70

21 - 30

0.60

31 - 45

0.50

46 - 60

0.45

61 - 120

0.20

> 120

Not Suitable

For SI: 1 minute per inch = min/25.4 mm, 1 gallon per square foot = 40.7 L/m

2

.

1403.1.2 Seepage trench excavations.

Seepage trench excavations shall be not less than 1 foot (304 mm) in width and not greater than 5 feet (1524 mm) in width. Trench excavations shall be spaced not less than 2 feet (610 mm) apart. The soil absorption area of a seepage trench shall be computed by using the bottom of the trench area (width) multiplied by the length of pipe. Individual seepage trenches shall be not greater than 100 feet (30 480 mm) in developed length.

1403.1.3 Seepage bed excavations.

Seepage bed excavations shall be not less than 5 feet (1524 mm) in width and have more than one distribution pipe. The absorption area of a seepage bed shall be computed by using the bottom of the trench area. Distribution piping in a seepage bed shall be uniformly spaced not greater than 5 feet (1524 mm) and not less than 3 feet (914 mm) apart, and greater than 3 feet (914 mm) and not less than 1 foot (305 mm) from the sidewall or headwall.

1403.1.4 Excavation and construction.

The bottom of a trench or bed excavation shall be level. Seepage trenches or beds shall not be excavated where the soil is so wet that such material rolled between the hands forms a soil wire. All smeared or compacted soil surfaces in the sidewalls or bottom of seepage trench or bed excavations shall be scarified to the depth of smearing or compaction and the loose material removed. Where rain falls on an open excavation, the soil shall be left until sufficiently dry so a soil wire will not form when soil from the excavation bottom is rolled between the hands. The bottom area shall then be scarified and loose material removed.

1403.1.5 Aggregate and backfill.

Not less than 6 inches in depth of aggregate, ranging in size from 1/2 to 2 1/2 inches (12.7 mm to 64 mm), shall be laid into the trench below the distribution piping elevation. The aggregate shall be evenly distributed not less than 2 inches (51 mm) in depth over the top of the distribution pipe. The aggregate shall be covered with approved synthetic materials or 9 inches (229 mm) of uncompacted marsh hay or straw. Building paper shall not be used to cover the aggregate. Not less than 9 inches (229 mm) of soil backfill shall be provided above the covering.

1403.2 Distribution piping.

Distribution piping shall be not less than 3 inches (76 mm) in diameter. Materials shall comply with

Table 1403.2

. The top of the distribution pipe shall be not less than 4 inches (100 mm) or greater than 12 inches (300 mm) below the original surface. The slope of the distribution pipes shall be not less than 2 inches (51 mm) and not greater than 4 inches (102 mm) per 100 feet (30 480 mm).

Table 1403.2 Distribution Pipe

Material

Standard

Polypropylene (PP) pipe

ASTM F 2389

Polyethylene (PE) plastic pipe

ASTM F 405

Polyvinyl chloride (PVC) plastic pipe

a

ASTM D 2729

Polyvinyl chloride (PVC) plastic pipe with a 3.5-inch O.D. and solid cellular core or composite wall

a

ASTM F 1488

a. Limited to residential buildings five stories or less in height.

1403.2.1 Joints and fittings.

Joints and fittings in distribution pipe shall be made in accordance with

Table 1403.2.1

.

Table 1403.2.1 Joints and Fittings

Material

Standard

Polyethylene (PE) plastic pipe

ASTM F 405

Polypropylene (PP) pipe

ASTM F 2389

Polyvinyl chloride (PVC) plastic in IPS diameters

a

ASTM D 2665; ASTM F 1866

Polyvinyl chloride (PVC) plastic pipe in sewer and drain diameters

a

ASTM D 3034

Polyvinyl chloride (PVC) plastic pipe with a 3.25-inch O.D.

a

ASTM D 2949

For SI: 1 inch = 25.4 mm.

a. Limited to residential buildings five stories or less in height.

1403.2.2 Diversion valves.

Systems shall include a diversion valve to divert gray water to the building sanitary system when soils are saturated or frozen, there is a blockage or backup in the system, the maximum allowed gallons per day is reached, or when system maintenance is necessary.

1403.2.3 Overflow connection.

Systems shall have a piped connection to the building drainage system to accommodate tank overflow.