64E-6.014. Construction Standards for Drainfield Systems

(1) Distribution box – where distribution boxes are used for distributing sewage from the septic tank or other waste receptacle to the drainfield lines, the following requirements shall be adhered to:

(a) Distribution boxes shall be watertight, constructed of durable materials, have adequate structural strength, and be of sufficient size to accommodate the required number of drain pipe lines.

(b) Each drainfield line shall be connected individually to the box.

(c) The invert of inlets to the box shall be at least 1 inch above the invert of the outlets. The invert of all outlets shall be level with respect to each other.

(d) The distribution box shall be built as a separate unit from the septic tank and shall be set level on solid ground or in mineral aggregate.

(2) Header pipe – header pipe, when used, shall be installed in compliance with the following requirements:

(a) Header pipe shall meet one or more of the following requirements:

1. ASTM D 3034-98, Standard Specification for Type PSM Poly (Vinyl Chloride)(PVC) Sewer Pipe and Fittings (1998), herein incorporated by reference.

2. ASTM D 2729-96 Standard Specification for Poly (Vinyl Chloride)(PVC) Sewer Pipe and Fittings (1996), herein incorporated by reference.

3. AASHTO M252M-96 Standard Specification for Corrugated Polyethylene Drainage Pipe (1996), herein incorporated by reference. Materials used to produce this pipe shall meet ASTM D 3350-98a, Standard Specification for Polyethylene Plastics Pipe and Fittings Materials (1998), Cell Classification 324420C, herein incorporated by reference.

4. ASTM F 405-97, Standard Specification for Corrugated Polyethylene (PE) Pipe and Fittings (1997), herein incorporated by reference. Materials used to produce this pipe shall meet ASTM D 3350-98a, Standard Specification for Polyethylene Plastics Pipe and Fittings Materials (1998), Cell Classification 324420C or E, herein incorporated by reference.

5. ASTM F 810-99, Standard Specification for Smoothwall Polyethylene (PE) Pipe for Use in Drainage and Waste Disposal Absorption Fields (1999), herein incorporated by reference. Materials used to produce this pipe shall meet ASTM D 3350-98a (1998), Standard Specification for Polyethylene Plastics Pipe and Fittings Materials, Cell Classification 32442C or E, herein incorporated by reference.

(b) Corrugated or smooth wall fittings (elbows, tees and crosses) shall be acceptable for gravity flow headers. Header pipe interior shall be smooth. Header pipe shall have a minimum inside diameter of 4 inches for gravity flow applications. Header pipe shall not be perforated.

(c) The header pipe shall be laid level with direct, connections to each drainfield line and the septic tank outlet pipe. When installed in a drainfield which uses mineral aggregate, the header pipe shall be encased in mineral aggregate, and shall be included as part of the drainfield area. Gravity flow header pipes, when installed within the mineral aggregate drainfield, may be non-watertight but shall be soil tight. Snap connections are acceptable. On non-mineral aggregate systems, header pipe must be supported by soil. All connections shall be such that all joints or fittings are firmly connected to pipes. When a drainfield system is a pumped system, the header pipe and fittings shall be smooth-walled and watertight. Where the header pipe is not within the absorption surface area it shall not be included in drainfield size calculations, but shall be considered part of the system. The header pipe shall be designed to distribute effluent as equally as practical to each individual drainline and shall be supported so that the header is laid level.

(d) Pipe which connects the septic tank outlet to the header pipe or a distribution box shall comply with the strength and material standards for header pipe as specified in this subsection.

(3) Low-Pressure dosing – where the total required area of drainfield is greater than 1000 square feet or where the applicant proposes to use low-pressure dosing, an automatic dosing device discharging into a low pressure distribution network consisting of 2 inch or smaller diameter schedule 40 PVC or equal pipe with 1/2 inch or smaller diameter drilled holes shall be used. All piping shall use solvent welded connections or equal throughout to prevent dislocation of connections under pressure. The network shall be designed for equal distribution of effluent. For the purposes of this section, equal distribution shall mean that the flow from the least effective hole in the network shall deliver no less than 75% of the flow from the most effective hole. The selected pump capacity (as measured in Gallons Per Minute) versus total dynamic head shall be indicated on a pump curve and shall be shown by calculation to achieve an effluent velocity through the network of at least 2 ft per second to the first exit hole on each lateral. Each line of the pressure network shall individually connect to a pressure manifold and be sealed on their distal ends and shall not be looped with other lines regardless of whether the drainfield is a bed or a trench or whether it is in a mound, filled subsurface installation. Plans and equipment specifications for low-pressure dosing systems shall be approved by the department prior to construction or installation.

(a) Where the total drainfield area is greater than 1000 square feet but not more than 2000 square feet, the applicant may, in lieu of low-pressure dosing, choose to split the drainfield into two drainfields, equal in size, each having no more than 1000 square feet, with each drainfield being lift-dosed.

(b) Dosing systems with 2000 square feet of drainfield or less shall consist of a pump tank that receives the flow from a septic tank or other sewage waste receptacle. Two pumps shall be required for commercial use where dosing is required due to drainfield size or where gravity flow into the drainfield is not possible, and estimated establishment sewage flows exceed 500 gallons per day. Where more than one pump is used, the pumps shall dose alternately. Where dosing is required for a commercial system for flows of 500 gallons or less per day, only one pump shall be required if the drainfield does not exceed 2000 square feet.

(c) Systems having more than 2000 square feet of drainfield shall have a minimum of two dosing pumps, with each pump serving a proportionate amount of the total required absorption area. The pumps shall dose alternately.

(d) The volume dosed between the pump operating levels shall be adequate to assure that the entire drain pipe network is filled at least four times each cycle.

(e) When a drainfield is installed in slightly limited soil, operating levels shall be adjusted to dose the drainfield a maximum of six times in a 24 hour period. For moderately limited soils the drainfield shall be dosed no more than four times in a 24 hour period. More frequent dosing may be allowed with systems designed by engineers licensed in the state of Florida.

(f) The distribution network for drainfields having an absorption area less than 1500 square feet shall be designed by a Florida licensed professional engineer or a master septic tank contractor. The network for drainfields having an absorption area of 1500 square feet or larger shall be designed by a Florida licensed professional engineer.

(g) Drip emitter systems shall be designed in accordance with subsection 64E-6.009(5), F.A.C.

(4) Lift dosing – Where a septic tank or sewage waste receptacle is placed too low to permit gravity flow into a properly designed, constructed and located drainfield, a pump tank with a pump or similar type device shall be used to lift the effluent to a properly constructed header pipe or distribution box for effluent distribution by gravity to the drainfield. This provision shall apply only to drainfields of 1000 square feet or less of total area. Tank size and pumps with effluent level controls and alarms shall be set in accordance with the requirements set forth in subsection 64E-6.013(9), F.A.C.

(5) Drain trenches and absorption beds – drain trenches and absorption beds are the standard subsurface drainfield systems used for disposing of effluent from septic tanks or other sewage waste receptacles. When used, these systems shall be constructed as specified below.

(a) When utilizing the standard drain trench method, the width of the trench at the bottom shall not exceed 36 inches. For trenches of 12 inches or less, there shall be a minimum separation distance of 12 inches between the sidewalls of adjacent trenches; trenches greater than 12 inches require a minimum 24 inch separation between the sidewalls of adjacent trenches.

(b) The trench method shall be the preferred method. Absorption beds may be used in lieu of the standard drain trench method. An absorption bed consists of an area in which the entire earth content of the required absorption area is removed and replaced with aggregate and distribution pipe or other approved alternative drainfield components. The distance between the centers of distribution lines in standard beds shall be a maximum of 36 inches. The distance between the sidewall of the bed and the center of the outside drain line shall be no more than 18 inches, but shall not be less than six inches. Where header pipe is used in lieu of a distribution box, the header shall extend to within 18 inches of the bed sidewalls. In no case shall the bottom surface of an absorption bed exceed a total of 1500 square feet. Where two or more beds are used to obtain the necessary absorption area, there shall be a minimum 10 foot separation between the sidewalls of adjacent absorption beds. Absorption beds shall be designed to achieve the maximum length to width ratio practical.

(c) When installing a drainfield system that uses mineral aggregate, all portions of the header pipe and perforated drain pipe shall be installed in aggregate conforming to ASTM C33-86 or lightweight aggregate conforming to ASTM C330-87 meeting State of Florida Department of Transportation (FDOT) specifications under Section 901, “Standard Specifications for Road and Bridge Construction, 1991” and the following gradation requirements.

Sieve	2 IN.	1 1/2 IN.	1 IN.	3/4 IN.	1/2 IN.	3/8 IN.	No. 4
size
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Percent	90-100	35-100	15-100	0-70	0-50	0-30	0-5
passing

In addition, not more than 3.75% by weight of the aggregate material at the point of use shall pass a #200 sieve.

1. Approved materials for drainfield mineral aggregate shall be limestone, slag, quartz rock, granite, river gravel, recycled crushed concrete, lightweight aggregate and other equally durable materials.

2. The aggregate shall be labeled as drainfield aggregate on the freight bill-of-lading. Effective March 1, 1995, a copy of the freight bill-of-lading shall be part of the documentation of aggregate size and quality and records shall be available for department review for a period of two years from the date of purchase. This bill-of-lading shall clearly certify that the material meets the requirements for drainfield use.

(d) Mineral aggregate material shall have a total depth of at least 12 inches extending throughout the width of the trench or absorption bed. The distribution pipe shall have a minimum of six inches of aggregate under the pipe, but shall not exceed 10 inches under the pipe when the total depth of aggregate is 12 inches.

(e) The drainfield in place shall be protected from infiltration of earth backfill by a barrier of polyester bonded filament. The barrier shall be placed on top of the drainfield only. For alternative drainfield systems any required earth backfill barrier shall be as specified by the alternative system manufacturer, which must be approved by the department at the time of the initial alternative drainfield approval.

(f) Providing the requirements of subsections 64E-6.006(1), (2) and (6), F.A.C., are met, the maximum depth from the bottom of the drainfield to the finished ground surface shall not exceed 30 inches after natural settling. The minimum earth cover over the top of the drainfield, distribution box or header pipe in standard subsurface drainfields shall be 6 inches after natural settling.

(g) The inside diameter of the drain pipe used in drainfields shall be determined based on the type and design of the proposed absorption system. However, for standard gravity aggregate drainfield systems, inside pipe diameter shall not be less than 4 inches. Perforated pipe shall have two rows of holes, and a minimum perforated area of 1 1/2 square inches per linear foot. Perforations shall be located not less than 30º or more than 60º from the vertical on either side of the center line of the bottom of the pipe. However, for drainfield systems designed by an engineer, drainpipe perforation area and hole configuration shall assure that effluent is distributed as equally as possible throughout the drainfield area. All plastic pipe shall conform to the standards of ASTM D 3034-98, Standard Specification for Type PSM Poly (Vinyl Chloride) (PVC) Sewer Pipe and Fittings (1998), herein incorporated by reference, ASTM F 405-97, Standard Specification for Corrugated Polyethylene (PE) Pipe and Fittings (1977), herein incorporated by reference, or ASTM F 810-99 (1999), herein incorporated by reference.

(h) Depending on the type of drainfield system being utilized, the drainfield absorption surface shall be constructed level or with a downward slope not exceeding one inch per 10 feet. Drain lines shall be placed at the same slope as the drainfield absorption surface.

(i) The maximum length of drain lines shall not exceed 100 feet for all gravity-fed and lift-dosed drainfields, and where two or more drain lines are used, they shall be, as near as practical, the same length. The ends of two or more drain lines in bed and mound systems shall be connected to produce a continuous circuit. A continuous circuit arrangement is also recommended but not required for standard drain trench systems. However, when a continuous circuit arrangement is not used, the distal ends of the drain lines shall be capped or sealed.

(j) No part of a drainfield shall be placed within 18 inches of the treatment or pump tank.

(k) If lots are encountered whereby a standard drainfield system cannot meet drainfield slope or soil cover requirements, a drop box configuration for sloping lots as per Section 7.2.8.1, Chapter 7, EPA 625/1-80-012, Design Manual for Onsite Wastewater Treatment and Disposal Systems, such section hereby incorporated by reference, may be used at the installer’s discretion for drainfield construction.

(6) All materials incorporated herein may be obtained from the Bureau of Onsite Sewage Programs at www.MyFloridaEH.com or 4052 Bald Cypress Way, Bin A08, Tallahassee, Florida 32399-1713.

Rulemaking Authority 381.0065(3)(a) FS. Law Implemented 381.0065 FS. History–New 12-22-82, Amended 2-5-85, Formerly 10D-6.56, Amended 3-17-92, 1-3-95, Formerly 10D-6.056, Amended 2-3-98, 3-22-00, 5-24-04, 11-26-06, 6-25-09, 7-16-13.