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• How to Abandon an Septic Tank
• Septic System, Septic Tank, & Cesspool Safety Warnings
• Septic Tank / Cesspool Collapse Warnings

This document outlines basic procedures for finding and safely abandoning unused septic systems and cesspools, and provides some safety suggestions for septic system inspectors, septic system inspections, septic pumping contractors, and home owners.

Septic tanks, cesspools, and drywells present serious hazards including septic cave-in's or collapses, methane gas explosion hazards, and asphyxiation hazards. Simple precautions which we describe here can help avoid a dangerous septic, cesspool, or drywell hazard. © 2008-1978 Daniel Friedman, All Rights Reserved. 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 are listed at "References."

This document is a chapter of Inspecting, Testing, & Maintaining Residential 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.

Guide to Proper Abandonment of Un-used Septic Tanks

It is important to properly abandon un-used septic tanks, cesspools, or drywells. If an old septic tank, cesspool, or drywell is simply "left alone" there may be very serious cave-in or fall-in safety hazards.

In addition to having been consulted in fatalities involving humans, we have learned that falling into septic tanks and cesspools is a risk for animals as well.

In 2008 Mark Cramer shared a report from an owner that that their horse fell into a septic tank and died tragically before it could be rescued. The collapsing septic tank was not in the location which the owners thought it would be found, and clearly it had an unsafe cover.

Septic Tank Abandonment Choices

When a septic tank is no longer going to be used, various factors determine what will happen to the old tank:

1. Cesspools & Drywells: If the old septic system component to be discontinued is a cesspool or drywell, and occasionally with septic tanks, the old tank might be left in place and "daisy chained" to the new one. This was common at country and farm properties that relied on a cesspool for onsite waste disposal. Owners hoped that the old system might still help a little with wastewater treatment and disposal even though it had stopped working. This approach is dangerous if the old system has an unsafe cover, is in danger of collapse, or is leaking where it should not be.
2. Steel septic tanks are often removed, crushed, and buried back at the site, possibly below or along side a new septic tank - details are below.
3. Concrete septic tanks are often filled-in after holes are broken into the tank - details are below.
4. Plastic or fiberglass septic tanks are a newer item with less experience in abandonment. If such a tank is badly damaged and leaky it needs to be removed and replaced. It may be possible to crush and bury such a tank as in the case of steel tanks.

To avoid the risk of a collapsing septic tank, cesspool, or drywell which is no longer used, it is important to find and properly close out such facilities at any property, residential or commercial. In the photo at the top of this page, the truck "found" an abandoned septic tank by driving over it.

Properly abandoning a septic tank, drywell, or cesspool which is no longer in use involves at least the following steps:

1. Locate all of the un-used septic tanks, cesspools, drywells on the property. At some properties there may be multiple systems and tanks, such as a chain of old cesspools or one or more septic tanks with a separate drywell. See these articles on finding hidden, lost, buried septic system components:

   • HOW TO FIND A SEPTIC TANK which offers detailed steps and multiple approaches, including our septic tank and drainfield location videos. An experienced plumber or septic contractor can assist in these steps and may have special equipment that speeds the process. These subtopics are addressed
     • SEPTIC SEARCH SAFETY
     • WHO KNOWS SEPTIC LOCATION?
     • FIND MAIN WASTE LINE EXIT
     • DISTANCE TO TANK
     • POSSIBLE SEPTIC TANK LOCATIONS
         VISUAL CLUES LOCATE TANK
         WHERE TO LOOK
         SEPTIC TANK DEPTH
     • SEPTIC TANK LOCATING EQUIPMENT
     • SEPTIC TANK COVERS
     • DOCUMENT TANK LOCATION
       
   • Find the Septic Tank an introduction to this topic with the basics of tank location
   • Special Septic Safety Warnings for Homeowners
     
     
2. Pump out the septic tank, cesspool, or drywell - a septic pumping contractor performs this step.
3. Break open the tank bottom - so that it won't hold surface runoff, forming an un-wanted water or mud reservoir. If the septic tank is steel, often the contractor will dig out the tank, crush it, and then bury it back in the original hole. When we installed a new concrete septic tank the contractor buried the crushed steel one on edge alongside the new concrete tank.
4. Fill in the septic tank, cesspool, or drywell, or hole where the tank was located (if you crushed an old steel tank) with stone, rubble, and soil so that there is on future collapse hazard.
5. Document the location of the filled-in items so that future site work or building plans can avoid or at least anticipate these buried obstructions.
6. If newer septic tanks, cesspools, or drywells remain in use at the property, be sure that their locations are documented (see DOCUMENT TANK LOCATION ) and that each of these has an intact, secure cover that will not cave in nor be easily opened by a child (see SEPTIC TANK COVERS ) We've written elsewhere about the importance of keeping livestock off of septic drainfields and septic tanks. There may be an extra risk of livestock-caused septic tank collapse where old septic tank or cesspool covers or even new fiberglass septic tanks and covers are installed.

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• Additional technical contributors & reference sources for this article are listed below.

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More Reading on Septic System Safety Hazards, Cesspool, Drywell, and Seepage Pit Safety Warnings

• Septic Safety: (this document) Septic System, Septic Tank, & Cesspool Safety Warnings for Septic Inspectors, Septic Pumpers, and Homeowners
• Cesspool Safety - Specific Warnings about Cesspool Collapse Hazards
• SEWER GAS ODORS: diagnosing, finding, and curing septic tank and sewer line odors


• Biomat Formation in the Septic System Drainfield Absorption System - what leads to drain field clogging and expensive drainfield repairs
• Cesspools for onsite wastewater disposal
• Drywells for onsite wastewater or graywater disposal
• Don't Flush these things into a septic system: a list of what's ok and what's not ok to put into septic tanks and building drains
• Septic Tank Location - How to Find the Septic Tank, how deep will the cover be, how to document its location - these methods also apply to locating a cesspool or drywell at a property.
• Inspecting & Testing Septic Systems: Online Book, Inspection, Test, Diagnosis, Repair, & Maintenance: Our Online Septic Book: Septic Testing, Loading & Dye Tests, Septic Tank Pumping, Clearances, details of onsite waste disposal system inspection, testing, repair procedures.
• Dye Tests: how to perform a Septic Loading and Dye Test - septic dye testing procedures in complete detail, a septic function test - a chapter in the above book.
• When Not to Pump a Septic Tank to avoid damage, unsafe conditions, or wasting money

• Alan Carson Carson Dunlop Associates, Toronto, Ontario. Mr. Carson is a home inspection professional, educator, researcher, writer, and a principal of Carson Dunlop Associates, a Toronto home inspection and education firm. Mr. Carson is a past president of ASHI, the American Society of Home Inspectors
• Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. (727) 595-4211 mark@BestTampaInspector.com 11/06 and 04/2008
• Hankey and Brown home inspectors, Eden Prairie, MN, technical review by Roger Hankey, prior chairman, Standards Committee, American Society of Home Inspectors - ASHI. 952 829-0044 - hankeyandbrown.com 11/06
• Arlene Puentes, a licensed home inspector, educator, and building failures researcher in Kingston, NY. 11/29/06
• John Francis, Bioworks, Inc., marketing and technical services - editing/proof reading 4/07. "BioWorks provides environmentally responsible, safe and cost-effective solutions to the agriculture industry"
• Thanks to Denise Cermola for permission to use the photo above, showing a dump truck collapsed into a seepage pit. (email 11/16/06 to 12/10/06). The contractor drove over this seepage pit connected to septic tank and caused total destruction of the system.
• Thanks to George Fielder who points out that methane gas is not toxic, but rather (we add) the hazards of methane gas produced by septic systems include possible explosions or the asphyxiation of someone who enters or even just leans over a septic tank opening. (email 10/20/2007)
• Thanks to Donica Ben who points out the danger of digging into buried electrical wires (11/11/07)

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.
• ...

More Information on Building Diagnostic Inspections and Repairs

• Cesspool Safety - Specific Warnings about Cesspool Collapse Hazards (this document)
• 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.
• When Not to Pump a Septic Tank to avoid damage, unsafe conditions, or wasting money
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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