Tanks

This chapter establishes the requirements for the design, installation, repair, and maintenance of septic tanks, treatment tanks, and holding tanks.

801 — General

801.1 Scope. The provisions of this chapter shall govern the design, installation, repair and maintenance of septic tanks, treatment tanks and holding tanks.

802 — Septic Tanks and Other Treatment Tanks

802.1 General. Septic tanks shall be fabricated or constructed of welded steel, monolithic concrete, fiberglass or an approved material. Tanks shall be water tight and fabricated to constitute an individual structure, and shall be designed and constructed to withstand anticipated loads. The design ofprefabricated septic tanks shall be approved. Plans for site-constructed concrete tanks shall be approved prior to construction.

802.2 Design of septic tanks. Septic tanks shall have not less than two compartments. The inlet compartment shall be not less than two-thirds of the total capacity of the tank, not less than a 500-gallon (1893 L) liquid capacity and not less than 3 feet (914 mm) wide and 5 feet (1524 mm) long. The secondary compartment of a septic tank shall have not less than a capacity of 250 gallons (946 L) and not more than one-third of the total capacity. The secondary compartment of septic tanks having a capacity more than 1,500 gallons (5678 L) shall be not less than 5 feet (1524 mm) long.

The liquid depth shall be not less than 30 inches (762 mm) and a maximum average of 6 feet (1829 mm). The total depth shall be not less than 8 inches (203 mm) greater than the liquid depth.

Rectangular tanks shall be constructed with the longest dimensions parallel to the direction of the flow.

Cylindrical tanks shall be not less than 48 inches (1219 mm) in diameter.

802.3 Inlets and outlets. The inlet and outlet on all tanks or tank compartments shall be provided with open-end coated sanitary tees or baffles made of approved materials constructed to distribute flow and retain scum in the tank or compartments. The inlet and outlet openings on all tanks shall contain a stop or other provision that will prevent the insertion of the sewer piping beyond the inside wall of the tank. The tees or baffles shall extend a minimum of 6 inches (152 mm) above and 9 inches (229 mm) below the liquid level, but shall not exceed one-third the liquid depth. A minimum of 2 inches (51 mm) of clear space shall be provided over the top of the baffles or tees. The bottom of the outlet opening shall be a minimum of 2 inches (51 mm) lower than the bottom of the inlet.

802.4 Manholes. Each compartment of a tank shall be provided with at least one manhole opening located over the inlet or outlet opening, and such opening shall be not less than 24 inches (610 mm) square or 24 inches (610 mm) in diameter. Where the inlet compartment of a septic tank exceeds 12 feet (3658 mm) in length, an additional manhole shall be provided over the baffle wall. Manholes shall terminate a maximum of 6 inches (152 mm) below the ground surface and be of the same material as the tank. Steel tanks shall have not less than a 2-inch (51 mm) collar for the manhole extensions permanently welded to the tank. The manhole extension on fiberglass tanks shall be of the same material as the tank and an integral part of the tank. The collar shall be not less than 2 inches (51 mm) high.

802.5 Manhole covers. Manhole risers shall be provided with a fitted, water-tight cover of concrete, steel, cast iron or other approved material capable of withstanding all anticipated loads. Manhole covers terminating above grade shall have an approved locking device.

802.6 Inspection opening. An inspection opening shall be provided over either the inlet or outlet baffle of every treatment tank. The opening shall be not less than 4 inches (102 mm) in diameter with a tight-fitting cover. Inspection pipes terminating above ground shall be not less than 6 inches (152 mm) above finished grade. Inspection pipes approved for terminating below grade shall be not more than 2 inches (51 mm) below finished grade, and the location shall be permanently recorded.

802.7 Capacity and sizing. The capacity of a septic tank or other treatment tank shall be based on the number of persons using the building to be served or on the volume and type of waste, whichever is greater. The minimum liquid capacity shall be 750 gallons (2839 L). Where the required capacity is to be provided by more than one tank, the minimum capacity of any tank shall be 750 gallons (2839 L). The installation of more than four tanks in series is prohibited.

802.7.1 Sizing of tank. The minimum liquid capacity for one- and two-family dwellings shall be in accordance with Table 802.7.1.

802.7.1 Sizing of tank. The minimum liquid capacity for one- and two-family dwellings shall be in accordance with Table 802.7.1.

A table appears here in the adopted code. Refer to the official source for the full table.

802.7.2 Other buildings. For buildings, the liquid capacity shall be increased above the 7S0-gallon (2839 L) minimum as established in Table 802.7.1. In buildings with kitchen or laundry waste, the tank capacity shall be increased to receive the anticipated volume for a 24-hour period from the kitchen or laundry or both. The liquid capacities established in Table 802.7.2 do not include employees. Exception: One- or two-family dwellings.

802.7.2 Other buildings. For buildings, the liquid capacity shall be increased above the 7S0-gallon (2839 L) minimum as established in Table 802.7.1. In buildings with kitchen or laundry waste, the tank capacity shall be increased to receive the anticipated volume for a 24-hour period from the kitchen or laundry or both. The liquid capacities established in Table 802.7.2 do not include employees.

Exception: One- or two-family dwellings.

802.8 Installation. Septic and other treatment tanks shall be located with a horizontal distance not less than specified in Table 802.8 between various elements. Tanks installed in ground water shall be securely anchored. A 3-inch-thick (76 mm) compacted bedding shall be provided for all septic and other treatment tank installations. The bedding material shall be sand, gravel, granite, limerock or other noncorrosive materials ofsuch size that the material passes through a O.S-inch (12.7 mm) screen.

A table appears here in the adopted code. Refer to the official source for the full table.

802.9 Backfill. The backfill material for steel and fiberglass tanks shall be specified for bedding and shall be tamped into place without causing damage to the coating. The backfill for concrete tanks shall be soil material, which shall pass a 4-inch (102 mm) screen and be tamped into place.

802.10 Manhole riser joints. Joints on concrete risers and manhole covers shall be tongue-and-groove or shiplap type and sealed water tight using neat cement, mortar or bituminous compound. Joints on steel risers shall be welded or flanged and bolted and water tight. Steel manhole extensions shall be bituminous coated both inside and outside. Methods of attaching fiberglass risers shall be water tight and approved.

802.11 Dosing or pumping chambers. Dosing or pumping chambers shall be fabricated or constructed of welded steel, monolithic concrete, glass-fiber-reinforced polyester or other approved materials. Manholes for dosing or pumping chambers shall terminate not less than 4 inches (102 mm) above the ground surface. Dosing or pumping chambers shall be water tight, and materials and construction specifications shall meet the same criteria specified for septic tanks in this chapter.

802.11.1 Capacity sizing. The working capacity of the dosing or pumping chamber shall be sized to permit automatic discharge of the total daily sewage flow with discharge occurring not more than four times per 24 hours. Minimum capacity of a dosing chamber shall be 500 gallons (1893 L) and a space shall be provided between the bottom of the pump and floor ofthe dosing or pumping chamber. A dosing chamber shall have a I-day holding capacity located above the high-water alarm for one- and two-family dwellings based on 100 gallons (379 L) per day per bedroom, or in the case of other buildings, in accordance with Section 802.7. Minimum pump chamber sizes are indicated for one- and two-family dwellings in Table 802.11.1. Where the total developed length of distribution piping exceeds 1,000 feet (305 m), the dosing or pumping chamber shall have two siphons or pumps dosing alternately and serving one-half of the soil absorption system.

802.11.1 Capacity sizing. The working capacity of the dosing or pumping chamber shall be sized to permit automatic discharge of the total daily sewage flow with discharge occurring not more than four times per 24 hours. Minimum capacity of a dosing chamber shall be 500 gallons (1893 L) and a space shall be provided between the bottom of the pump and floor ofthe dosing or pumping chamber. A dosing chamber shall have a I-day holding capacity located above the high-water alarm for one- and two-family dwellings based on 100 gallons (379 L) per day per bedroom, or in the case of other buildings, in accordance with Section 802.7. Minimum pump chamber sizes are indicated for one- and two-family dwellings in Table 802.11.1. Where the total developed length of distribution piping exceeds 1,000 feet (305 m), the dosing or pumping chamber shall have two siphons or pumps dosing alternately and serving one-half of the soil absorption system.

A table appears here in the adopted code. Refer to the official source for the full table.

802.12 Design of other treatment tanks. The design of other treatment tanks shall be approved on an individual basis. The capacity, sizing and installation of the tank shall be in accordance with this section except as otherwise approved. Where a treatment tank is preceded by a conventional septic tank, credit shall be given for the capacity of the septic tank.

803 — Maintenance and Sludge Disposal

803.1 Maintenance. Septic tanks and other treatment tanks shall be cleaned whenever the sludge and scum occupy one-third of the tank's liquid capacity.

803.2 Septage. All septage shall be disposed of at an approved location.

804 — Chemical Restoration

804.1 General. Products for chemical restoration or chemical restoration procedures for private sewage disposal systems shall not be used unless approved.

A table appears here in the adopted code. Refer to the official source for the full table.

805 — Holding Tanks

805.1 Approval. The installation of a holding tank shall not be approved where the site can accommodate the installation of any other private sewage disposal system specified in this code. A pumping and maintenance schedule for each holding tank installation shall be submitted to the code official.

805.2 Sizing. The minimum liquid capacity of a holding tank for one- and two-family dwellings shall be in accordance with Table 805.2. Other buildings shall have a minimum 5-day holding capacity, but not less than 2,000 gallons (7570 L). Sizing shall be in accordance with Table 802.7.2. Not more than four holding tanks shall be installed in series.

A table appears here in the adopted code. Refer to the official source for the full table.

805.3 Construction. Holding tanks shall be constructed of welded steel, monolithic concrete, glass-fiber reinforced polyester or other approved materials.

805.4 Installation. Tanks shall be located in accordance with Section 802.8, except the tanks shall be not less than 20 feet (6096 mm) from any part of a building. Holding tanks shall be located so the servicing manhole is located not less than 10 feet (3048 mm) from an all-weather access road or drive.

805.5 Warning device. A high-water warning device shall be installed to activate 1 foot (305 mm) below the inlet pipe. This device shall be either an audible or an approved illuminated alarm. The electrical junction box, including warning equipment junctions, shall be located outside the holding tank or housed in waterproof, explosion proof enclosures. Electrical relays or controls shall be located outside the holding tank.

805.6 Manholes. Each tank shall be provided with either a manhole not less than 24 inches (610 mm) square or a manhole with a 24-inch (610 mm) inside diameter extending not less than 4 inches (102 mm) above ground. Finish grade shall be sloped away from the manhole to divert surface water from the manhole. Each manhole cover shall have an effective locking device. Service ports in manhole covers shall be not less than 8 inches (203 mm) in diameter and shall be 4 inches (102 mm) above finished grade level. The service port shall have an effective locking cover or a brass cleanout plug.

805.7 Septic tank. The outlet shall be sealed where an approved septic tank is installed to serve as a holding tank. Removal of the inlet and outlet baffle shall not be prohibited.

805.8 Vent. Each tank shall be provided with a vent not less than 2 inches (51 mm) in diameter and shall extend not less than 12 inches (305 mm) above finished grade, terminating with a return bend fitting or approved vent cap.

Frequently asked questions

What types of tanks are regulated by this chapter?

This chapter governs septic tanks, treatment tanks, and holding tanks.

When should septic or other treatment tanks be cleaned?

Tanks must be cleaned when sludge and scum collectively occupy one-third of the tank's liquid capacity.

Can chemical products be used for private sewage system restoration?

No, products or procedures for chemical restoration of private sewage disposal systems are prohibited unless specifically approved.

Under what conditions can a holding tank be approved?

Holding tanks are only approved if the site cannot accommodate any other specified private sewage disposal system, and a pumping and maintenance schedule is submitted.