Current through Register Vol. 47, No. 17, September 10, 2024
A. Design criteria
for all graywater treatment works
The following minimum design criteria are required for all
graywater treatment works. All graywater treatment works must meet and/or
comply with the following requirements:
1. Meet all design requirements of this
regulation and meet any additional design requirements of the Colorado Plumbing
Code.
2. Each treatment component
or combination of multiple components must have a design flow greater than the
calculated peak graywater production, if upstream of the storage tank or if no
tank is present.
3. Include a
diversion valve that directs graywater to either the graywater treatment works
or a closed sewerage system. The diversion valve must be:
a. Easily operable;
b. Clearly labeled;
c. Constructed of material that is durable,
corrosion resistant, watertight;
d.
Designed to accommodate the inlet and outlet pipes in a secure and watertight
manner; and
e. Indirectly connect
the bypass line to the closed sewerage system.
4. Not have any piping that allows the
treatment process(es) or storage tank to be bypassed prior to graywater
use.
5. Include a tank to collect
and store graywater, except for a subsurface irrigation system that discharges
to a mulch basin. The storage tank must:
a. Be
constructed of durable, non-absorbent, watertight, and corrosion resistant
materials;
b. Be closed and have
access openings for inspection and cleaning;
c. Be vented:
i. for indoor tanks: the tanks must be vented
to the atmosphere outside of the house;
ii. for outdoor tanks: the storage tank must
have a downturned and screened vent;
d. Have an overflow line:
i. with the same or larger diameter line as
the influent line;
ii. without a
shut off valve;
iii. that is
trapped to prevent the escape of gas vapors from the tank; and
iv. that is indirectly connected to the
closed sewerage system;
e. Have a valved drain line with the same or
larger diameter line as the influent line that is indirectly connected to the
closed sewerage system;
f. Be a
minimum of 52 gallons;
g. Be placed
on a stable foundation;
h. If
located outdoors, not be exposed to direct sunlight; and
i. Have a permanent label that states
"CAUTION! NON-POTABLE WATER. DO NOT DRINK."
6. For indoor toilet or urinal flushing
systems (Categories C1 and C2) graywater treatment works must have a backup
potable water system connection. For subsurface irrigation systems (Categories
B1 and B2) graywater treatment works may, but are not required to, have a
backup potable water system that provides potable irrigation water when
graywater is not being produced or is produced in insufficient quantities. All
backup potable water system connections must meet the following requirements:
a. For non-public water systems, potable
water system connections: uncontrolled cross connections between a potable
water system and a graywater treatment works are prohibited. All cross
connections must be protected by a reduced pressure principle backflow
prevention zone assembly or an approved air gap.
b. For public water systems, potable water
system connections: uncontrolled cross connections between a public water
system and a graywater treatment works are prohibited. The graywater treatment
works design must protect the public water system from cross connections by
meeting the requirements of Regulation No. 11: Colorado Primary Drinking Water
Regulations.
7. Not be
used as a factor to reduce the design, capacity or soil treatment area
requirements for OWTS designs per Regulation No. 43 On-site Wastewater
Treatment System Regulation or domestic wastewater treatment works designs per
Regulation No. 22 Site Location and Design Regulations for Domestic Wastewater
Treatment Works.
8. Have any
wastewater from graywater treatment works (e.g., filter backwash water) be
properly contained and disposed into a closed sewerage system or an approved
Underground Injection Control (UIC) well.
9. Have all graywater piping clearly
distinguished and clearly labeled, including pipe identification and flow
arrows.
10. If located in a
100-year floodplain area, meet or exceed the requirements of FEMA and the local
emergency agency. The graywater treatment works must be designed to minimize or
eliminate infiltration of floodwaters into the system and prevent discharge
from the system into the floodwaters.
11. Not be located in floodways.
12. Be located within the confines of the
legal property boundary and not within an easement.
B. Design criteria for subsurface irrigation
systems, including mulch basins (Applicable to Graywater Use Categories: A1, B1
and B2)
1. All subsurface irrigation systems
(Applicable to Graywater Use Categories: A1, B1 and B2):
The following minimum design criteria are required for all
graywater treatment works being used for subsurface irrigation. All subsurface
graywater irrigation systems must comply with the following
requirements:
a. Have the subsurface
irrigation components of the graywater irrigation system installed a minimum of
two inches (2") and a maximum of twelve inches (12") below the finished grade.
b. Have the subsurface irrigation
components of the graywater irrigation system installed in suitable soil, as
defined in section 86.8(44).
c.
Have a minimum of twenty-four inches (24") of suitable soil between the
subsurface irrigation components of the graywater irrigation system and any
restrictive soil layer, bedrock, concrete, or the highest water table.
Restrictive soil layers are soil types 4, 4A, and 5 in Table 12-2.
d. Include controls, such as valves,
switches, timers, and other controllers, as appropriate, to ensure the
distribution of graywater throughout the entire irrigation zone.
e. If utilizing emitters, the emitters must
be designed to resist root intrusion and be of a design recommended by the
manufacturer for the intended graywater flow and use. Minimum spacing between
emitters shall be sufficient to deliver graywater at an agronomic rate and to
prevent surfacing or runoff.
f.
Have all irrigation supply lines be polyethylene tubing or PVC Class 200 pipe
or better and Schedule 40 fittings. All joints shall be pressure tested at 40
psi (276 kPa), and shown to be drip tight for five minutes before burial. Drip
feeder lines can be poly or flexible PVC tubing.
g. Meet the following setback distances in
Table 12-1.
Table 12-1: Graywater Treatment Works Setback
Requirements
|
Minimum Horizontal Distance Required
from:
|
Graywater Storage
Tank
|
Irrigation Field
|
|
Buildings
|
5 feet
|
2 feet
|
|
Property line adjoining private property
|
10 feet
|
10 feet
|
|
Property line adjoining private property with
supporting property line survey
|
1.5 feet
|
1.5 feet
|
|
Water supply wells
|
50 feet
|
100 feet
|
|
Streams and lakes
|
50 feet
|
50 feet
|
|
Seepage pits or cesspools
|
5 feet
|
5 feet
|
|
OWTS disposal field
|
5 feet
|
25 feet
|
|
OWTS tank
|
5 feet
|
10 feet
|
|
Domestic potable water service line
|
10 feet
|
10 feet
|
|
Public water main
|
10 feet
|
10 feet |
h.
The irrigation field must be located on slopes of less than thirty percent
(30%) from horizontal.
i. Protocols
for determining the size of the subsurface irrigation area:
The irrigation area must be determined using one of the
following protocols.
i) Site
evaluation protocol: The following site evaluation must be conducted to
determine the appropriate size of the irrigation area for all subsurface
irrigation systems.
The site evaluation must include:
(a) Site information, including:
(1) a site map; and
(2) location of proposed graywater irrigation
area in relation to physical features requiring setbacks in Table 12-1.
(b) Soil investigation
to determine long-term acceptance rate of a graywater irrigation area as a
design basis. Soil investigation must be completed by either:
(1) a visual and tactile evaluation of soil
profile test pit, or
(2) a
percolation test.
(c)
Irrigation rates must not exceed maximum allowable soil loading rates in Table
12-2 for Laundry to Landscape systems (Graywater Use Category A1), and Table
12-3 for dispersed subsurface irrigation systems (Graywater Use Categories B1
and B2), based on the finest textured soil in the twenty-four inches (24") of
suitable soil beneath the subsurface irrigation components.
(d) Suitable soil may consist of original,
undisturbed soil or original soil that is augmented. Not suitable soil may be
augmented as needed to ensure suitable soil is used.
(e) If the original soil is augmented, the
mixture used for augmentation must meet the following criteria to ensure that
suitable soil is achieved:
(1) The mixture
must have an organic content that is at least five percent (5%) and no greater
than ten percent (10%);
(2) The
mixture must be a well blended mix of mineral aggregate (soil) and compost
where the soil ratio depends on the requirements for the plant species;
and
(3) The mineral aggregate must
have the following gradation:
|
Sieve Size
|
Percent Passing
|
|
3/8
|
100
|
|
No. 4
|
95 - 100
|
|
No. 10
|
75 - 90
|
|
No. 40
|
25 - 40
|
|
No. 100
|
4 - 10
|
|
No. 200
|
2 - 5 |
(f) If the original soil is augmented, the
additional soil must be tilled into the native soil a minimum of six inches
(6") below irrigation application zone.
2. Mulch basin irrigation system
requirements (Applicable to Graywater Use Category: A1)
The following minimum design criteria are required for
graywater treatment works using mulch basin systems for subsurface irrigation
(Applicable to Graywater Use Category: A1):
a. Design Specifications: System includes
only laundry machine discharge water to a mulch basin that is pressurized
solely through the laundry machine discharge hose and is not treated, filtered,
or stored.
b. Mulch shall be
permeable enough to allow infiltration of graywater.
c. Piping to mulch basins must discharge a
minimum of two inches (2") below grade into a container for dispersal of
graywater into the mulch basin. The container must be designed to have two
inches (2") of freefall between the invert of the discharge pipe and the
maximum depth of water in the mulch basin. The container must have an access
lid for observation of flow and to check mulch levels.
d. The mulch basin must have a minimum depth
of twelve inches (12") below grade and not more than twenty-four (24") below
grade.
e. A filter is not required
for installation.
f. The following
irrigation area equation protocols must be used to determine the appropriate
size of the mulch basin in square feet for single family, Laundry to Landscape
systems. Use equation (i) if actual graywater flow is unknown, and equation
(ii) if known. Refer to Table 12-2: Soil Type Description and Maximum Hydraulic
Loading Rate for LRG.
Table 12-2: Soil Type Description and Maximum
Hydraulic Loading Rate
|
Soil Type
|
USDA Soil Texture
|
USDA Structure - Shape
|
USDA Soil Structure-Grade
|
Percolation Rate (MPI)
|
Loading Rate for Graywater (LRG) (gal./sq.
ft./day)
|
|
0
|
Soil Type 1 with more than 35% Rock
(>2mm);
Soil Types 2-5 with more than 50% Rock
(>2mm)
|
--
|
0 (Single Grain)
|
Less than 5
|
Not suitable without augmentation 1.0 with
augmentation
|
|
1
|
Sand, Loamy Sand
|
--
|
0
|
5-15
|
Not suitable without augmentation
1.0 with augmentation
|
|
2
|
Sandy Loam, Loam, Silt Loam
|
PR BK GR
|
2 (Moderate) 3 (Strong)
|
16-25
|
0.8
|
|
2A
|
Sandy Loam, Loam, Silt Loam
|
PR, BK, GR 0 (none)
|
1 (Weak) Massive
|
26-40
|
0.6
|
|
3
|
Sandy Clay Loam, Clay Loam, Silty Clay Loam
|
PR, BK, GR
|
2, 3
|
41-60
|
0.4
|
|
3A
|
Sandy Clay Loam, Clay Loam, Silty Clay Loam
|
PR, BK, GR
0
|
1 Massive
|
61-75
|
0.2
|
|
4
|
Sandy Clay, Clay, Silty Clay
|
PR, BK, GR
|
2, 3
|
76-90
|
Not suitable
|
|
4A
|
Sandy Clay, Clay, Silty Clay
|
PR, BK,
GR 0
|
1 Massive
|
91-120
|
Not suitable
|
|
5
|
Soil Types 2-4A
|
Platy
|
1, 2, 3
|
121+
|
Not suitable |
i. LA = maximum
gallons per day allowed/LRG
Where:
The maximum gallons per day allowed is 250 gallons; and
LRG is the loading rate for graywater from Table 12-2;
or
ii. LA = estimated actual
graywater flow per day/LRG
Where:
The estimated actual graywater flow is derived in
86.11(A)(1)(a)(ii) and;
LRG is the loading rate for graywater from Table 12-2.
g. Soil types 0
and 1 in Table 12-2 must be augmented before use. Soil type 4, 4A, and 5 in
Table 12-2 are not suitable for subsurface irrigation.
3. Dispersed subsurface irrigation system
requirements (Applicable to Graywater Use Categories: B1 and B2):
The following minimum design criteria are required for
graywater treatment works using dispersed irrigation systems for subsurface
irrigation:
a. Include a cartridge
filter, which must meet the following requirements:
i. A minimum of 60 mesh;
ii. Located between the storage tank and the
irrigation system;
iii. If a pump
is being used to pressurize the graywater distribution system, the filter must
be located after the pump.
b. The following irrigation area equation
protocols must be used to determine the appropriate size of the irrigation area
for single family and non-single family, dispersed subsurface irrigation
systems (Applicable to Graywater Use Categories B1 and B2). Refer to Table
12-3: Soil Type and Maximum Absorption Capacity in gallons per square foot of
irrigation area per day.
Table 12-3: Soil Type and Maximum Absorption Capacity
|
2024 Uniform Plumbing Code Soil
Type
|
2024 Uniform Plumbing Code Maximum
absorption capacity in gallons per square foot of irrigation area per
day
|
|
Course sand or gravel
|
5.0
|
|
Fine Sand
|
4.0
|
|
Sandy loam
|
2.5
|
|
Sandy clay
|
1.7
|
|
Clay with considerable sand or gravel
|
1.1
|
|
Clay with small amounts of sand or gravel
|
0.8 |
i. LA = gpd/MAC
in gal/ft2
Where:
Gpd = gallons per day per household or non-single family
combined (actual graywater flow is derived in 86.11(A)(1)(a) for single family,
86.11(A)(1)(b) for non-single family)
MAC = maximum absorption capacity in gallons per square foot
C. Design criteria for indoor toilet and
urinal flushing graywater treatment works (Graywater Use Categories C1 and C2)
1. Category C1: single family, indoor toilet
and urinal flushing graywater treatment works
The following minimum design criteria are required for
graywater treatment works for Category C1: single family, indoor toilet and
urinal flushing:
a. The graywater
treatment works must be certified under "Class R" of NSF/ANSI 350 Onsite
Residential and Commercial Water Reuse Treatment Systems.
b. If a disinfection process is not part of
NSF/ANSI 350-2011 equipment, separate disinfection system equipment is
required. For graywater treatment works that use sodium hypochlorite (bleach),
the graywater treatment works must be capable of providing a free chlorine
residual of 0.2 to 4.0 mg/L in the graywater throughout the indoor graywater
plumbing system.
c. The graywater
treatment works must include a dye injection system that is capable of
providing a dye concentration that is visibly distinct from potable water.
d. For Category C1 indoor toilet
and urinal flushing graywater treatment works that are also capable of using
graywater for subsurface irrigation, the system may be designed to allow
graywater to be diverted to the subsurface irrigation graywater treatment works
prior to the disinfection and dye process, however after the point of diversion
the subsurface irrigation portion of the system must meet the requirements in
section 86.12(B).
2.
Category C2: non-single family, indoor toilet and urinal flushing graywater
treatment works
The following minimum design criteria are required for
Category C2: non-single family, indoor toilet and urinal flushing:
a. The graywater treatment works must be
certified under "Class R" or "Class C" of NSF/ANSI 350 Onsite Residential and
Commercial Water Reuse Treatment Systems. Required classification shall be
dictated by the size of the graywater treatment works and if the graywater
sources are residential or commercial as defined by NSF/ANSI 350.
b. Separate disinfection system equipment is
required if a disinfection process is not part of NSF/ANSI 350-2011 equipment.
A graywater treatment works must be capable of providing a free chlorine
residual of 0.2 to 4.0 mg/L in the graywater throughout the indoor graywater
plumbing system.
c. The graywater
treatment works must include a dye injection system that is capable of
providing a dye concentration that is visibly distinct from potable water.
d. For Category C2 indoor toilet
and urinal flushing graywater treatment works that are also capable of using
graywater for subsurface irrigation, the system may be designed to allow
graywater to be diverted to the subsurface irrigation graywater treatment works
prior to the disinfection and dye process, however after the point of diversion
the subsurface irrigation portion of the system must meet the requirements in
section 86.12(B).
e. For graywater
treatment works that have a capacity to receive greater than 2,000 gallons per
day, the design must be prepared under the supervision of and submitted with
the seal and signature of a professional engineer licensed to practice
engineering in the State of Colorado in accordance with the requirements of the
Colorado Department of Regulatory Agencies (DORA) - Division of Professions and
Occupations.
D.
Design criteria for rural fire protection graywater treatment works (Graywater
Use Categories D1 and D2)
1. Category D1:
single family, rural fire protection graywater treatment works
The following minimum design criteria are required for
graywater treatment works for Categories D1: single family, rural fire
protection:
a. The graywater treatment
works must be authorized by the local fire protection district and meet minimum
treatment requirements of the local fire protection district in addition to the
design criteria included herein.
b.
The graywater treatment works must be certified under "Class R" NSF/ANSI 350
Onsite Residential and Commercial Water Reuse Treatment Systems.
c. If a disinfection process is not part of
NSF/ANSI 350-2011 equipment, separate disinfection system equipment is
required. For graywater treatment works that use sodium hypochlorite (bleach),
the graywater treatment works must be capable of providing a free chlorine
residual of 0.2 to 4.0 mg/L prior to graywater entering the storage
cistern.
d. For Category D1
graywater treatment works that are also capable of using graywater for
subsurface irrigation or indoor fixture flushing, the system may be designed to
allow graywater to be diverted to the subsurface irrigation graywater treatment
works prior to the dye process, however after the point of diversion the
subsurface irrigation portion of the system must meet the requirements in
section 86.12(B).
2.
Category D2: non-single family, rural fire protection graywater treatment works
The following minimum design criteria are required for
graywater treatment works for Categories D2: non-single family, rural fire
protection:
a. The graywater treatment
works must be authorized by the local fire district/authority and meet minimum
treatment requirements of the local fire district/authority in addition to the
design criteria included herein.
b.
The graywater treatment works must be certified under "Class R" or "Class C" of
NSF/ANSI 350 Onsite Residential and Commercial Water Reuse Treatment Systems.
Required classification shall be dictated by the size of the graywater
treatment works and if the graywater sources are residential or commercial as
defined by NSF/ANSI 350.
c. If a
disinfection process is not part of NSF/ANSI 350-2011 equipment, separate
disinfection system equipment is required. For graywater treatment works that
use sodium hypochlorite (bleach), the graywater treatment works must be capable
of providing a free chlorine residual of 0.2 to 4.0 mg/L prior to graywater
entering the storage cistern.
d.
For Category D2, rural fire protection graywater treatment works that are also
capable of using graywater for subsurface irrigation or indoor fixture
flushing, the system may be designed to allow graywater to be diverted to the
subsurface irrigation graywater treatment works prior to the dye process,
however after the point of diversion the subsurface irrigation portion of the
system must meet the requirements in section 86.12(B).
e. For graywater treatment works that have a
capacity to receive greater than 2,000 gallons per day, the design must be
prepared under the supervision of and submitted with the seal and signature of
a professional engineer licensed to practice engineering in the State of
Colorado in accordance with the requirements of the Colorado Department of
Regulatory Agencies (DORA) - Division of Professions and Occupations.
