S.C. Code Regs. § § 61-56.504

Current through Register Vol. 48, No. 11, November 22, 2024

Section 61-56.504 - Fiberglass Reinforced Plastic Tanks Standard

Standards describing fiberglass reinforced plastic septic tanks have been adopted to ensure a quality product of sufficient strength and resistance, capable of fulfilling its intended purpose. Many of these standards were derived from NBS Voluntary Product Standard PS 15-69, which covers custom contact-molded reinforced polyester chemical resistant process equipment.

504.1. General Requirements.

The following general requirements are applicable to fiberglass reinforced plastic septic tanks as defined within this regulation, and approved design standards and structural properties of the same shall be not less than those stated.

(1) Material

Resins and sealants used in the tank manufacturing process shall be capable of effectively resisting corrosive influences of liquid components of sewage, gases generated by the digestion of sewage, and soil burial. Materials used shall be formulated to withstand vibration, shock, normal household chemicals, earth, and hydrostatic pressure both when full and empty. Not less than thirty (30) percent of the total weight of the tank shall be fiberglass reinforcement. For tanks not exceeding a fifteen hundred (1500) gallon liquid capacity, the minimum wall thickness shall be three-sixteenths (3/16) inch, provided, however, that isolated small spots may be as thin as eighty (80) percent of the minimum.

(2) Inner Coating

Internal surfaces shall be coated with an appropriate gel coating to provide a smooth, pore-free, watertight surface for fiberglass reinforced plastic parts.

(3) Physical Properties

Tanks shall be so constructed that all parts of the tank shall meet the following requirements:

(a) Ultimate Tensile Strength (Minimum) - Nine thousand (9,000) pounds per square inch (psi) when tested in accordance with ASTM D 638-7la, Standard Method of Test for Tensile Properties of Plastics.

(b) Flexural Strength (Minimum) - Sixteen thousand (16,000) psi when tested in accordance with ASTM D 790-71, Standard Method of Test for Flexural Properties of Plastics.

(c) Flexural Modulus of Elasticity Tangent (Minimum) - Seven hundred thousand (700,000) psi when tested in accordance with ASTM D 790-71, Standard Method of Test for Flexural Properties of Plastics.

(4) Watertight Integrity

Tanks shall be so constructed as to be watertight for the designed life of the tank. Lids or covers shall be sufficiently tight when installed to preclude the entrance of surface or ground water into the tank.

(5) Longevity

Proof from an independent testing laboratory shall be submitted substantiating a minimum life expectancy of twenty years of service for the intended use of the tank and appurtenant components such as necessary sealants, connective fastenings, resins, etc.

(6) Safety

As a safety measure, provisions shall be made in the construction of septic tank lids or covers to preclude unauthorized entry or removal when the use of the tank necessitates positioning of access openings at or above ground level.

(7) Workmanship

Tanks shall be of uniform thickness and free from defects that may affect their serviceability or durability. Completed tanks shall have a smooth inside finish free of spills, pits, and honeycombs. Plant quality control shall be sufficient to maintain a high degree of uniformity in tank quality.

504.2. Specific Requirements.

Specific requirements for design and construction shall be not less than those specified herein and shall be in conformity with recognized National Standards for design and construction and in accordance with this regulation.

504.3. Capacity and Design Limits.

(1) Dimensions

(a) The inside length of a horizontal cylindrical tank shall be at least two (2) but not more than three (3) times the width.

(b) The uniform liquid depth shall not be less than four (4) feet.

(c) At least fifteen (15) percent of the total volume of the tank shall be above the liquid level.

(d) If tanks of other shapes are proposed, specifications must be submitted to the Department for approval.

(2) Inlet

(a) Provisions shall be made for the building sewer to enter the center of one end of the septic tank two (2) inches above the normal liquid level of the tank.

(b) A tee shall be constructed as an integral part of the tank to receive the building sewer, or as an alternative, an integrally constructed baffle may be used.

(c) If baffles are used, suitable integrally fitted sleeves or collars shall be provided in the inlet openings of the tank to provide surface areas sufficient to ensure capability of watertight bonding between the tank and the inlet sewer.

(d) If the tee or baffle is constructed of plastic material, it shall meet NSF Standard #14 for drain, waste, and vent system application.

(e) If fiberglass reinforced plastic is used, it shall be of the same constituency as material of which the tank is constructed.

(f) The inlet tee or baffle shall extend sixteen (16) inches below the designed liquid level and be placed and secured in a vertical position so as to be watertight and preclude dislodgement during installation, operation, or maintenance activities.

(3) Outlet

(a) Provisions shall be made for the outlet sewer to receive the discharge from the tank by providing an opening in the center of the end of the tank opposite the inlet, the invert elevation of which shall be at the liquid level of the tank.

(b) A tee shall be constructed as an integral part of the tank to connect to the outlet sewer or, as an alternative, an integrally constructed baffle may be used.

(c) If baffles are used, suitable integrally fitted sleeves or collars shall be provided in the outlet opening of the tank to provide surface areas sufficient to ensure capability of watertight bonding between the tank and the outlet sewer.

(d) If the tee or baffle is constructed of plastic material, it shall meet NSF Standard #14 for drain, waste, and vent system application.

(e) If fiberglass reinforced plastic is used, it shall be of the same constituency as material of which the tank is constructed.

(f) The outlet tee or baffle shall extend eighteen inches below the design liquid level and be placed and secured in a vertical position so as to be watertight and preclude dislodgement during installation, operation, or maintenance activities.

(g) The inlet and outlet tees shall extend above liquid level a minimum of six (6) inches and to no less than one (1) inch from the top of the tank to allow venting between tank compartments and multiple tank configurations.

(4) Access Openings

Openings in the top of the septic tank shall be provided over the inlet and outlet tees or baffles with sufficient area to enable maintenance service to such tees or baffles.

(5) Identifying Markings

Fiberglass septic tanks shall be provided with a suitable legend, cast or stamped into the wall at the outlet end, and within six inches of the top of the tank, identifying the manufacturer, and indicating the liquid capacity of the tank in gallons.

S.C. Code Regs. § 61-56.504

Added by State Register Volume 45, Issue No. 05, eff. 5/28/2021.