6.1. Each distribution zone shall have a
minimum effective irrigation area for the soil characteristics and vegetation
needs.
6.2. The area of a
distribution zone shall be equal to the total length of the perforated pipe
sections within the distribution zone multiplied by the width of the proposed
trench. The required square footage shall be determined using Table 4 or Table
5.
TABLE 4
Subsurface Irrigation System Design
|
Soil Characteristics
|
Subsurface Irrigation System Area Loading, gallons of
graywater per day per square foot
|
|
Coarse Sand or Gravel
|
5
|
|
Fine Sand
|
4
|
|
Sandy Loam
|
2.5
|
|
Sandy Clay Loam
|
1.6
|
|
Clay Loam
|
1.1
|
|
Clay with Sand or Gravel
|
0.8
|
TABLE 5
Drip Irrigation System Design
|
Soil Characteristics
|
Minimum Number of Emitters, per gallon per day
|
Maximum Emitter Discharge, gallons per day
|
|
Coarse Sand or Gravel
|
0.6
|
1.8
|
|
Fine Sand
|
0.7
|
1.4
|
|
Sandy Loam
|
0.9
|
1.2
|
|
Sandy Clay Loam
|
1.1
|
0.9
|
|
Clay Loam
|
1.6
|
0.6
|
|
Clay with Sand or Gravel
|
2.0
|
0.5
|
6.3.
The lowest point of any distribution zone shall be at least two vertical feet
above the maximum groundwater table. Applicant shall provide sufficient
groundwater data to the regulatory authority. Subsection R317-4-4.1.B.4 may be
used to determine maximum groundwater elevation.
6.4. Subsurface drip irrigation system.
Subsurface drip irrigation systems shall be constructed so
that:
(a) A 140 mesh or 115 micron
filter with a capacity of 25 gallons per minute minimum shall be used to
prevent drip irrigation system clogging;
(b) The filter backwash and flush discharge
shall be captured, contained, and discharged to the sewer system or approved
onsite wastewater system;
(i) filter backwash
water and flush water may not be used for any purpose;
(ii) sanitary procedures shall be followed
when handling filter backwash and flush discharge of graywater;
(c) Emitters recommended by the
manufacturer shall be resistant to root intrusion and suitable for subsurface
and graywater dispersal;
(d) Each
irrigation zone shall include the minimum number of emitters required to meet
the daily graywater flows as defined in Table 5;
(e) Minimum spacing between emitters should
be 12 inches in any direction, or as recommended by the manufacturer;
(f) The system shall provide user controls
such as valves, switches, timers, and other controls as appropriate, to rotate
the discharge of graywater between distribution zones;
(g) All drip irrigation force mains and
manifolds shall:
(i) meet requirements of
Table 7;
(ii) be connected with
schedule 40 fittings;
(iii) be
connected as per manufacturer's specifications, inspected and pressure tested
at 40 pounds per square inch and shown to be drip tight for five minutes,
before burial; and
(iv) be buried
at a minimum depth of six inches;
(h) Lateral distribution lines may be PE or
flexible PVC tubing and shall be covered to a minimum depth of six
inches;
(i) Pressure at the emitter
shall meet the manufacturer's recommendations; and
(j) Each distribution zone shall include a
flush valve, and where applicable, an anti-siphon valve to prevent back
siphonage of water and soil.
6.5. Subsurface Irrigation System.
Subsurface irrigation systems consisting of pipe and gravel
or chambers may be used for dispersal of graywater.
(a) Perforated pipe sections shall be a
minimum three-inch diameter and shall be constructed of perforated high-density
polyethylene pipe, perforated ABS pipe, perforated PVC pipe, or other approved
materials as required in Table 7, provided that sufficient openings are
available for distribution of the graywater in the trench area. Material,
construction and perforation of the piping shall be in compliance with the
requirements of the International Plumbing Code and local building
code.
(b) A subsurface irrigation
system shall be constructed in accordance with Table 6.
(c) Aggregate shall be placed in the trench
to the depth and grade required by Table 6. The aggregate shall then be covered
with barrier material to prevent closure of voids with backfill.
(d) Chamber systems shall be installed as per
manufacturer's specifications. All chambers shall meet requirements listed in
Rule R317-4.
(e) Backfill may not
be placed over the barrier material or chambers prior to inspection and
approval by the regulatory authority.
TABLE 6
Lateral Construction Details
|
Description
|
Minimum
|
Maximum
|
|
Number of drain lines per zone
|
1
|
---
|
|
Length of each perforated line, feet
|
---
|
150
|
|
Bottom width of trench, inches
|
6
|
36
|
|
Total depth of trench, inches
|
9
|
36
|
|
Spacing of lines, wall to wall, feet
|
4
|
---
|
|
Depth of backfill, inches
|
6
|
---
|
|
Depth of aggregate cover over lines, inches
|
2
|
---
|
|
Depth of aggregate beneath lines, inches
|
3
|
---
|
|
Grade of drain lines, inches per 100 feet
|
Level
|
4
|
TABLE 7
Minimum Standards for Graywater Sewer and Distribution Pipe
Materials (a)
Acceptable Graywater Pipe Materials
|
Type of Pipe
|
Minimum Standard
|
|
Acrylonitrile-Butadiene Styrene (ABS)
|
ASTM (b), D-2680, D-2751, F-628
|
|
Polyvinyl Chloride (PVC)
|
ASTM D-2665, D-3033, D-3034
|
Acceptable Distribution Pipe Materials
|
Type of Pipe
|
Minimum Standard
|
|
ABS
|
ASTM D-2661, D-2751
|
|
Polyethylene (PE)
|
Smooth Wall ASTM D-3350
|
|
PVC
|
ASTM D-2665, D-3033, D-3034, D-2729(c)
|
Notes:
(a) Each
length of graywater sewer and distribution pipe shall be stamped or
marked.
(b) American Society for
Testing and Materials.
(c) Although
perforated PVC, ASTM D-2729 is approved for absorption system application, the
solid-wall version of this pipe is not approved for any application.
