5 Colo. Code Regs. § 1002-86.12

Current through Register Vol. 47, No. 20, October 25, 2024

Section 5 CCR 1002-86.12 - Graywater Treatment Works - Design Criteria

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.

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).

5 CCR 1002-86.12

38 CR 11, June 10, 2015, effective 6/30/2015

38 CR 23, December 10, 2015, effective 12/30/2015

46 CR 24, December 25, 2023, effective 1/14/2024