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This chapter discusses soil percolation rate specifications - what are the required soil perc rates when testing for septic system absorption system or drainfield design or repair.

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PERC TEST STANDARDS - What are the soil percolation rate standards and other soil requirements for septic systems?

The Massachusetts Title 5 Septic Inspection criteria does a great job of defining a (at least possibly) what is required to assure a functional septic drainfield. The text explains the role of the biomass below the absorption bed, sets soil depth requirements, and recognizes the importance of keeping the bottom of the working biomass area in well drained soil sufficiently above the seasonal high water table.

Here is an example of soil requirements for a functional drainfield. This version is particularly clearly written and is for residents of Ohio but the principles apply anywhere. Readers should also see our example of state-regulated soil percolation tests at the New York State Septic System Design Regulations 75-A.4 - Soil and site evaluation for septic system design page.

In Ohio, soil absorption systems can be used in areas where the percolation rate of the soil is between 3 and 60 minutes per inch (soil permeability between 1 and 20 inches per hour).

At least 4 feet of suitable soil is required under the soil absorption system to provide adequate treatment of the septic tank effluent. To accommodate the construction of the system and provide adequate soil cover to grade, a minimum of 5 1/2 to 6 1/2 feet of suitable soil is needed above the limiting layer.

A limiting layer may be bedrock, an impervious soil layer (hardpan, fragipan) or a seasonally high water table (gray soil or mottles). The soil absorption system must be at least 8 feet from any drain line on the lot, 50 feet from a water supply, and 10 feet from the property line, right-of-ways and the house. Septic systems cannot be placed on the flood plain and are limited to areas with less than a 15 percent slope. Reference: ohioline.osu.edu/aex-fact/0743.html Ohio State University Fact Sheet Septic Tank - Soil Absorption Systems

Our separate article by Lockwood includes a description of the calculations to answer the question: How Big Should the Leach Field Be? and includes a practical example using sample calculations as well as a table of soil percolation rate vs. the necessary leach field size.

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SEPTIC SYSTEMS HOME
SEPTIC SYSTEMS ONLINE BOOK
SEPTIC SYSTEM DESIGN BASICS
  Septic Soil PERC TESTS
  WHAT ARE PERC TESTS
  PERC HOLE SPECIFICATIONS
  PERC STANDARDS
  SEPTIC TANK SIZE
  SEPTIC TANK DEPTH
  SEPTIC TANK TEES
  SEPTIC DRAINFIELD SIZE
  SEPTIC DRAINFIELD SHAPE
  SEPTIC CLEARANCES
  SEPTIC TANK PUMPING FREQUENCY
  SEPTIC TANK PUMPING PROCEDURE
  SEPTIC PUMPING REPAIR
  SEPTIC TREATMENTS
SEPTIC DESIGN ALTERNATIVES

• New York State Septic System Design Regulations 75-A.4 - Soil and site evaluation for septic system design
• "The Soil Media and Percolation Test," Paul D. Robillard, Kelli S. Martin, Penn State College of Agriculture, Cooperative Extension, Agricultural Engineering Fact Sheet SW-163
• SEPTIC SYSTEM DESIGN BASICS
• SEPTIC SYSTEM DESIGN ALTERNATIVES

The Septic Systems Online Book - Where Are We?

• This Chapter: SEPTIC SOIL & PERC TESTS Next Chapter: SEPTIC TANK SIZE
• First Chapter: SEPTIC SYSTEMS ONLINE BOOK

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
• The Septic System Information Website home page for this topic
• Septic Systems Inspection, Testing, & Maintenance- online textbook. Detailed how to inspect, maintain, repair information
• The Home Buyer's Guide to Septic Systems
• Septic Tank Pumping Guide: When, Why, How to pump the septic tank
• Home & Outdoor Living Water Requirements
• Septic Tank Capacity vs Usage in Daily Gallons of Wastewater Flow, calculating required septic tank size, calculating septic tank volume from size measurements
• How Big Should the Leach Field Be? - table of soil percolation rate vs. field size
• Septic System Drainfield Absorption System Biomat Formation - what leads to drain field clogging and expensive drainfield repairs
• Table of Required Septic & Well Clearances: Distances Between Septic System & Wells, Streams, Trees, etc.
• Ten Steps to Keeping a Septic System Working, suggestions from the U.S. EPA, edits and additions by DJF
• Pennsylvania State Fact Sheets relating to domestic wastewater treatment systems include
• Pennsylvania State Wastewater Treatment Fact Sheet SW-161, Septic System Failure: Diagnosis and Treatment
• Pennsylvania State Wastewater Treatment Fact Sheet SW-162, The Soil Media and the Percolation Test
• Pennsylvania State Wastewater Treatment Fact Sheet SW-l64, Mound Systems for Wastewater Treatment
• Pennsylvania State Wastewater Treatment Fact Sheet SW-165, Septic Tank-Soil Absorption Systems
• Document Sources used for this web page include but are not limited to: Agricultural Fact Sheet #SW-161 "Septic Tank Pumping," by Paul D. Robillard and Kelli S. Martin. Penn State College of Agriculture - Cooperative Extension, edited and annotated by Dan Friedman (Thanks: to Bob Mackey for proofreading the original source material.)
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