Guide to Proper Abandonment of Un-used Septic Tanks

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Safety Concerns in Abandoning Septic Systems, Seepage Pits, Cesspools, Drywells, even dug wells 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. 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. Readers should also see specific warnings about cesspools at CESSPOOL SAFETY. Watch out: for unsafe septic tanks and cesspools or drywells and for systems that were not properly abandoned. 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. We were consulted in a Long Island death of an adult who fell into and was buried in a collapsing cesspool. And in 2012 we were contacted for comment involving the death of two boys who fell into and perished in an “abandoned” septic tank or cesspool that lacked a safe cover. See SEPTIC & CESSPOOL SAFETY. 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. Septic tank, drywell, or cesspool abandonment or tank closure may involve complete tank removal, tank crushing (steel septic tanks), or most common with site-built tanks/cesspools/drywells, and with concrete tanks, the cover is opened and the tank is filled-in with rubble and soil. Details of septic tank, cesspool, drywell abandonment procedures are discussed in this article.

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 alongside 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.