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Life Expectancy & Cost of No-Rock Gravelless Septic Systems InspectAPedia®  -

• Typical life & typical installation costs of gravelless or no-rock septic designs
• Design manual for gravelless or no rock septic fields
• No-rock or chamber septic drainfield product descriptions, sources
• Septic leaching field product cost comparisons
• Septic absorption field capacity & life comparisons
• Septic Systems - Design, Inspection, Testing, & Maintenance

This chapter discusses the typical life expectancy and typical installation cost of a gravelless or "no gravel" or "no rock" septic drainfield system. Drainfields, also called leach fields, absorption beds, soil absorption systems, and leaching beds, perform the functions of septic effluent treatment and disposal in onsite wastewater treatment systems, conventionally called "septic systems".

These systems can provide an acceptable effluent disposal system for sites with limited space for a drainfield or where gravel is not available or is quite expensive.

Advanced septic treatment methods are discussed in separate chapters. Citation of this article by reference to this website and brief quotation for the sole purpose of review are permitted. Use of this information at other websites, in books or pamphlets for sale is reserved to the author. Technical review by industry experts has been performed and is ongoing - reviewers welcomed and are listed at "References." This document is a chapter of Inspecting, Testing, & Maintaining Residential Septic Systems an online book on septic systems.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

Life Expectancy of Gravelless Septic Systems

To date we have not received study data comparing the life expectancy of a conventional gravel trench drain field with that of a gravelless drainfield in equivalent soils and usage rates. In either type of absorption system ultimately the biomat and soils around the absorption system trench become clogged, the rate of clogging depending on usage, soil characteristics, maintenance of the septic tank (frequent pumping extends drain field life), and what is put into the wastewater (salts, grease, other products reduce drainfield life).

Ultimately the capacity of the absorption system is a function of the area of soil being used to dispose of effluent around the effluent distribution system (trench width and depth, and surface area exposed to effluent).

OPINION: I would expect that for two alternative below-ground effluent disposal system designs such as a gravel trench or a chamber system, if installed in the same soils and at identical original capacity, there will be no difference in the length of the service life of the installation.

There may be differing costs, however, in subsequent system repair or replacement. For example, does the failed system need to be excavated and removed in one case but not another?

Installation Cost for Gravelless Septic Systems

The primary waste line, septic tank, and distribution piping costs are unaffected by the use of these septic effluent absorption system alternatives, except that some of the choices such as the chamber system are asserted (by Infiltrator Systems Inc.) to use fewer linear feet of material in the absorption field (about half) - a factor that must be taken into consideration in pricing the installation cost.

The trenches may need to be wider or in some instances deeper, however - which will affect the excavation cost. Some writers suggest that even if a manufacturer claims that you can use less trench length with a no-gravel system you should instead opt for the larger capacity (and probably longer life) provided by not skimping on total trench lengths. However, for a small site with limited space for an absorption field, the added capacity of a gravelless system may be a solution.

Consumers expecting to save in the installation cost of their drainfield by using a no-gravel or "gravelless" septic effluent disposal system should compare all of the costs involved. The savings in gravel and possibly excavation cost (shorter trenches) needs to be weighed against the added cost for the special products (described above) to distribute the septic effluent to the soil.

OPINION: I expect that in all cases the excavation cost is going to dominate the absorption system total cost. It is possible that option 4 described above will have the smallest excavation cost because it can be installed in a very narrow trench, perhaps cut with a smaller specialized machine such as is used for running buried wires and pipes.

We are polling manufacturers for installation costs for gravel-less drainfield alternatives and will post that data here as it becomes available.

Keep in mind that cost comparisons among onsite wastewater handling systems can be specious. It makes little sense to compare the costs of two different systems when only one of them would actually work at a given site. Therefore I advise that you first determine what your site requires because of its soil, space, and so on. Then you can compare alternatives that would work on that site.

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• Additional technical contributors & reference sources for this article are listed below.
• Crumpler Plastic Pipe, Inc. Crumpler provides fabric-wrapped drainage piping 800-334-5071 Roseboro NC USA - "No-Rock TM Septic-Leachate drainpipe systems" are available in 8" and 10" systems.
• Jeff Pildis, Technical Service & Support, Infiltrator Systems, Inc. 800-718-2754
• Daniel Friedman - principal author/editor of the InspectAPedia ^TM Website

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

SEPTIC DESIGN ALTERNATIVES
  AEROBIC SEPTIC SYSTEMS
  ALTERNATING BED SEPTIC SYSTEMS
  CESSPOOLS
  DRYWELLS
  SEPTIC EFFLUENT DISINFECTION SYSTEMS
  EVAPORATION-TRANSPIRATION SEPTIC SYSTEMS
  FIXED-FILM PROCESS SEPTIC SYSTEMS

  GRAVELLESS SEPTIC SYSTEMS
  Polystyrene-wrapped perforated pipe
  Geotextile-Wrapped Perforated Pipe
  Chamber Systems
  Site Requirements / Design Criteria
  Construction Details
  Life Expectancy of No Rock Septic Designs
  Installation Cost of No Rock Septics
  Gravelless Septic Product Sources

  LAGOON SEPTIC SYSTEMS
  MEDIA FILTER SEPTIC SYSTEMS
  SEPTIC & GREYWATER FILTERS
  SEQUENCING BATCH SEPTIC SYSTEMS
  MOUND SEPTIC SYSTEMS
  RAISED BED SEPTIC SYSTEMS
  SAND BED SEPTIC SYSTEMS
  SEWAGE TREATMENT SYSTEMS
  TOILET ALTERNATIVES
  VEGETATED SUBMERGED SEPTIC BEDS
  WETLAND SEPTIC SYSTEMS
  ALTERNATIVE SEPTIC DESIGNERS
  ALTERNATIVE SEPTIC PRODUCTS

More Reading:

SEPTIC SYSTEM DESIGN BASICS
How Big Should the Leach Field Be? includes a practical example using sample calculations and a table of soil percolation rate vs. field size
Design Basics for Septic Systems: Choosing Septic Tank Size, Leach Field Size - basic septic system volume and absorption system design guides.
Components of a Septic System- the Basic Parts of a Conventional Septic Tank and Leachfield, a chapter in the Home Buyers Guide to Septic Systems
Sketches of the Septic System Components Private Sewage Disposal Systems - Septic Drawing Library
Cesspools for more in-depth information about those systems.
Drywells for more in-depth information about those systems.]
SEPTIC SYSTEM DESIGN ALTERNATIVES
(1) (2) (3) (4) APPENDIX 75-A to Public Health Law, 201(1)(1) NEW YORK STATE WASTEWATER TREATMENT STANDARDS - INDIVIDUAL HOUSEHOLD SEPTIC SYSTEMS. Portions of the text of this web page (using paragraphs identified by parenthetical numbers (1)-(4)) are quoted from this document, expanded with edits and additions by this author
"Gravelless Drainfields, Recommended Standards and Guidance for Performance, Application, Design and Operation & Maintenance", Washington State Department of Health, an MS Word .doc file available at: www.doh.wa.gov/ehp/ts/WW/Gravelless2004.doc

More Information on Building Diagnostic Inspections and Repairs

• 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.

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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