Rock Laterals

A conventional rock lateral system, (gravity feed), is the most common system used either on level land or moderate slopes with adequate soil depth above the water table or other restrictive horizon. Heavy solids in the sewage settle and greases float to the top of the septic tank. In addition, bacteria break down some of the solids. The liquid or effluent flows from the septic tank through solid piping to distribution box (es) and then into perforated piping within gravel filled trenches, where it then seeps into the soil. As the liquid slowly moves through the soil, bacteria and oxygen purify the liquid. Regular pumping of the septic tank reduces the solids discharged into the trench and extends the life of the system. Septic tanks should be pumped every three to five years to prevent solids from leaving the tank.

The total length of the trenches are determined by comparison of total daily waste flow into the system and the absorption capability of the soil. No trench can be greater than 100 feet in length and are ideally 24 inches deep and 24 inches wide. There is a minimum distance of 18 inches below the bottom of the trench to the depth of rock, water table, and/or a restrictive horizon. Washed or fragmented clean rock (size will depend on availability), is to be used in the system. The trench has 6 inches of rock in the bottom, a section of 4 inch perforated pipe and then 2 inches of additional rock is placed over the pipe and leveled. A total of 12 inches of rock will be in the trench. A barrier material of, straw, hay or synthetic polyester, must cover the rock in the trench to prevent soil from clogging the trench rock and perforated pipe when the trench is covered with soil.

The system may require modification due to the depth of rock, water table and/or a restrictive horizon. Note, the minimum distance between the bottom of the trench and these conditions is 18 inches. Therefore, if the bottom of the trench is less than 24 inches below the surface, top soil must be added.

Advantages:
This system can be used on either level or moderately sloping lots. However, it may be necessary to align the adsorption field along the contour planes of the slope.

Restrictions / Requirements:
Typically this system uses the most space of any conventional system. A minimum of 10 feet spacing, measured from the center of each trench, must be allowed to achieve an adequate absorption area.

There must be at least a usable trench depth of 6 inches to use this system. In addition, the use of a modified system may require a variance received from the local or district health department. All systems install should be properly permitted and inspected by the appropriate health department.

Leaching Chambers

Leaching chamber systems function like a conventional rock lateral system but without rock. They are used on level to moderately level lots with adequate soil depth above the water table or other restrictive horizon. The liquid flows from the septic tank through solid piping to distribution box(es) and then into open bottom chambers that create an underground cavern that stores the effluent. The effluent floods the soil surface prior to seeping vertically through the bottom of the trench allowing soil bacteria and oxygen to purify it. Since no rock is used, nearly all of the soil surface of the trench bottom and side wall is exposed and available to treat effluent.

The chambers are constructed in sections approximately six foot long and three foot wide. They may be installed in either trench or bed configuration. The individual sections snap or screw together and contain end caps to complete the line.

Other Topics:
Caring For Your Septic System - Do's & Don'ts | Common Onsite Regulations | Curtain Drain, Washer lines and Filters | Engineering and Design for Difficult Sites | Fill & Wait - Why? What? How? | Improve Your System Practice Water Conservation | Potential Property Owners Reference | Septic Systems - How do they work? | Ten Most Asked Questions About Septic Systems | Why Systems Fail | Sewage Protection Program

Barrow Company specializes in the engineering and design of all types of systems. If you would like additional information on these or any other system, please use the Contact Us section on this website, e-mail us at info@barrowcompany.com or contact us by telephone or fax. Office hours are 7:30 a.m. to 4:30 p.m. Monday thru Friday