Photograph of Don't fall into a septic tank - it's likely to be fatal. Septic Tank, Cesspool & Drywell Safety Warnings
Safety procedures for & warnings about inspecting, servicing, or working on septic tanks, drywells, cesspools

  • SEPTIC & CESSPOOL SAFETY - home: CONTENTS: Septic System, Septic Tank, & Cesspool Safety Warnings & procedures. Septic Tank / Cesspool Dangers for septic inspectors, septic pumpers, & homeowners. Septic fall-in video
  • POST a QUESTION or READ FAQs about safety hazards around septic tanks & cesspools

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

This document provides important safety warnings for septic systems and cesspools, and provides some safety suggestions for septic system inspectors, septic system inspections, septic pumping contractors, and home owners.

Green links show where you are. © Copyright 2015, All Rights Reserved.

SEPTIC & CESSPOOL SAFETY GUIDE - Septic System, Septic Tank, & Cesspool Safety Warnings

Providing inspection and diagnosis of on-site waste disposal systems is an extremely valuable public service which helps protect people from expensive unanticipated septic system repair costs and helps protect public health by assuring sanitary disposal of sewage and gray water waste from buildings.

More importantly though, septic system inspections may detect and warn about serious safety hazards at some properties.

The strong warnings issued below intend to reduce septic system safety hazards for inspectors and property owners/occupants, but it is not the author's intention to dissuade inspectors from providing this valuable service.

Watch out: 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 or expensive septic problem.

The septic hazard news video at right recounts a child falling into a septic tank and a separate septic fall-in fatality.

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.

Examples & Case Reports of Fatal Hazards at Open or Insecure Septic Tank, Cesspool, Drywell Covers

LARGER IMAGE-1 of a septic catastrophe - walk the site, find possible tank locations, don't step through the cover LARGER IMAGE-2 of a septic catastrophe - walk the site, find possible tank locations, don't step through the cover LARGER IMAGE-3 of a septic catastrophe - walk the site, find possible tank locations, don't step through the cover

Safety Warning: there is a very high risk of fatal falls into septic tanks, cesspools, or drywells: danger lurks at cesspools, open covers, tanks or tank covers in poor condition, and from high levels of methane gas CH4 or hydrogen sulfide H2S.

These septic system dangers include the risk of collapse, falling, asphyxiation, explosion, and other potentially fatal hazards as well as risks of unsanitary conditions such as bacterial or viral infections. This hazard is more than theoretical. We have personally assisted in investigation of several septic or cesspool fall-in fatalities and are aware of others.

Caravan site debris and site hazards (C) Daniel Friedman Caravan site debris and site hazards (C) Daniel Friedman

Inspecting a mobile park housing migrant workers at a New York farm, Steven Vemilye and Daniel Friedman documented various immediate and serious safety hazards at two open or semi-open septic tanks and cesspools. Shown above is a home-made dry-laid concrete block well (unstable) surrounding an open septic tank.

The property manager left the concrete septic tank cover off and just tossed a light section of plywood over the system in order to make frequent septic tank pumping easier. This mobile home collection was occupied by many families including families with small children. An adult or child falling into an open septic tank is very likely to die quickly.

Caravan site debris and site hazards (C) Daniel Friedman Caravan site debris and site hazards (C) Daniel Friedman

Above Mr. Vermilye, accompanied by the attorney who had asked us to perform a site inspection, was demonstrating the instability of the covers over septic facilities at this location. [As we document
at MOBILE HOMES, DOUBLEWIDES, TRAILERS, we report with regret that Mr. Vermilye passed away on 19 June 2001.]

Watch out: Readers trying to diagnose and deal with sudden soil subsidence or yard collapses should
see CESSPOOL SAFETY WARNINGS as those hazards can also apply to drywells and septic tanks, and


There can be other unexpected hazards when inspecting building sites and septic systems. In the photo series above, the author was inspecting the home shown from outside before looking in the crawl space to locate the main waste line exit point and thus before predicting the probable location of the septic tank.

Walking close to this house should have set off an alarm about possible unsafe conditions: poor maintenance, old home, of an age likely to have used a steel septic tank. In fact the author found the tank very quickly by stepping through its cover, avoiding serious injury or even possible fatality mostly by luck. It was throw myself sideways into the briars and garbage at the site or fall completely into the septic tank.

A Safety Guide for Septic System Inspection, Cleaning, Pumping, and Homeowner Care

  • Don't work alone at a septic tank, cesspool, or drywell: Falling into a septic tank or even leaning over a septic tank can be fatal. Do not work on or at septic tanks alone - workers can become suddenly overcome by methane gas.
  • Do not ever enter a septic tank or cesspool unless you are specially trained and are wearing the special equipment and gear for that purpose, including self-contained breathing apparatus.
  • Do not go into a septic tank to retrieve someone who has fallen in and was overcome by toxic gases unless you are equipped with a self-contained breathing apparatus (SCBA). If a SCBA is not available, call for emergency services and put one or more fans at the top of the septic tank to blow in fresh air.
  • Don't lean over a septic tank opening: Do not lean over or stick your head into the septic tank to examine its interior - you could fall in to the tank or become overcome by gases and fall into the tank, an event which is likely to be fatal.
  • Don't ignite flames Do not light a flame at or near the tank - methane gas is explosive. At one tank pump out my client described the explosion and burns received by the pumping contractor when he stood by the tank and lit a cigarette. A reader reported a stunning methane gas explosion that damaged nearby buildings when a brush fire was built over a septic tank. [There are safer ways to find the septic tank.]
  • Site must be ventilated: Decomposing wastes in the septic tank produce toxic or otherwise dangerous gases (such as methane which is both explosive and in a septic tank methane gas is an asphyxiant) which can kill a human in a matter of minutes. When working on a tank be sure the area is well ventilated.
  • Rope off & Mark Dangerous Sites: If your inspection discover that there are dangerous conditions, such as an unsafe tank cover, tank collapse, or a home-made septic tank or cesspool (which are at increased risk of sudden collapse) such areas should be roped off and clearly marked as dangerous to prevent access until proper evaluation and repairs can be made.
  • Safe cesspool, drywell, or septic tank covers are required: be sure that the tank and its access ports have sound and secure covers that do not risk collapse and which cannot be removed by children.
  • Septic & Cesspool Collapse Hazards: Old steel tanks, thin, rusting steel or rotting home-made wood tank covers, site-built tanks and cesspools, and recently-pumped cesspools are at particular risk of collapse. Falling into a septic tank or cesspool is likely to lead to rapid asphyxiation from methane and in cases of collapse, there is risk of becoming buried. The author has consulted in cases involving such fatalities (homeowner fell into a site-built cesspool), and at one site inspection, walking near an overgrown area the author himself stepped through a rusting steel septic tank top, surviving only by throwing himself into a nearby clump of brambles! Beware of the following additional septic system inspection hazards:
    • Bad septic tank covers: flimsy, rusted, old-steel, home-made, or missing septic tank/drywell/cesspool covers
    • Abandoned septic tanks: systems which may not have been filled-in
    • Collapsed, or collapsing septic tanks or cesspools
    • Additional unexpected septic components: possible presence of multiple components at a property, abandoned or in-use
    • Un-stable soils: Cesspools and septic systems in areas of unstable soils or areas of commonly-found site-built systems - collapse risk
    • Cesspool pumping or agitating: pumping, aerating, or agitating cesspools in an attempt to restore function can lead to sudden collapse of these systems, especially if the cesspool or septic tank was "site built" using stacked concrete blocks or stone
  • Shock & Electrical Hazards: when digging outdoors, watch out that you don't dig into and cut an electrical wire (or other buried mechanical line such as a gas or water line). Buried electrical wires can look a lot like tree roots. Chopping through an electrical wire while digging to find a septic system can be dangerous. [Thanks to Donica Ben for reminding us of this septic safety problem.]
  • Unsanitary conditions: Be alert for unsanitary conditions such as surface effluent or sewage backups into buildings, events which risk serious viral and bacterial hazards and which indoors, may require professional cleaning. Be alert for personal sanitation hazards when working around septic systems, such as open cuts or failure to wash properly after working on systems.
  • Damage to Septic Components: Avoid damaging septic system components or the building: Improper septic testing procedures, such as flooding a dosing-system, can damage the system. Also, remember to check for leaks into or under the building being tested when running water into the building fixtures and drains. Don't leave water running unattended - at risk of flooding the building.

Do not drive over the septic tank or septic piping

PHOTO of a septic seepage pit collapse when a truck drove over it.

Unless special provisions have been made such as protection of sewer piping and septic tanks from damage, vehicle-rated septic tank covers, or similar steps, do not drive vehicles over the septic system.

Driving over septic tanks, septic piping, or drainfields risks costly damage to the septic system and may also be dangerous.

The bulldozer in our photo (left) was called to help remove a truck which drove over septic system components leading to a surprise collapse.

If a septic line must be run under a driveway, for example to pass from a building to the septic tank, the line must be protected by choice of materials (schedule 40), or placed in a covered and protected trench at adequate depth (such as with concrete covers over the trench) to avoid damage.

If a septic tank is to be located below a drive or parking area, it too must be properly designed and protected from collapse.

A septic drainfield cannot be located below a driveway or parking area. Doing so will prevent proper drainfield operation due to soil compaction and also due to loss of proper evaporation of moisture through the surface, as well as almost certainly leading to crushed broken piping.

Methane Gas Hazards around Septic Systems, Methane Gas Toxicity vs. Methane Explosion & Asphyxiation Risks, How to Measure Methane Gas Levels

Methane Gas Hazards are primarily of explosion or asphyxiation - see METHANE GAS HAZARDS for details.

We commented above at Septic System Safety that methane gas which maybe encountered in septic system is both explosive and an asphyxiant.

A thoughtful reader, George Fielder, previously a salesperson for GfG Instrumentation, pointed out that these are the hazards. (We had inaccurately stated that methane gas was "toxic".)

Readers who need more details about the safety concerns regarding methane gas in and around septic systems should be sure to review the septic system methane gas hazards and measurement and references cited at SEPTIC METHANE GAS (also see Septic Methane Gaslinks listed at the "More Reading" links at the bottom of this article in this article)

Guide to Proper Abandonment of Un-used Septic Tanks

PHOTO of a septic seepage pit collapse when a truck drove over it.

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.

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:
  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 SEPTIC TANK LOCATION SKETCH ) and that each of these has an intact, secure cover that will not cave in nor be easily opened by a child

    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.


Continue reading at CESSPOOL SAFETY WARNINGS or select a topic from the More Reading links shown below.

Suggested citation for this web page

SEPTIC & CESSPOOL SAFETY at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

More Reading

Green link shows where you are in this article series.


Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

HTML Comment Box is loading comments...

Technical Reviewers & References

Publisher's Google+ Page by Daniel Friedman

Click to Show or Hide Citations & References