LARGER IMAGE: a steel septic tank with a rusted cover was located in this walking area. A photo of the steel septic tank cover after the author
stepped through it is shown below. Septic Tank Condition - How to Inspect Steel Septic Tanks

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Steel septic tank warnings:

This document describes how to inspect the condition of a septic tank, providing special considerations for inspecting steel septic tanks. Inspecting steel septic tanks is a key component in onsite wastewater disposal systems.

We describe steels septic tank defects, life expectancy, special problems, and repair methods. The page top photo shows an area where the author walked just before stepping through a rusted-out steel septic tank cover (shown below).

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

STEEL SEPTIC TANKS - Life Expectancy, What Breaks, What to Look For, How to Fix a Damaged or Leaky Steel Septic Tank or Tank Cover or Baffle

Photo of a collapsing steel septic tank location

Steel septic tanks typically last 20-25 years, then rust, and collapse.

Before this time steel baffles may rust off (damaging the drain field with sludge), the tank top may become rusty and unsafe, or the tank bottom may have rusted through.

You can see the steel septic tank baffle in the lower left of this photo - notice that the top edges of the baffle have rusted away?

In the photo shown here the steel septic tank cover had rusted through and was covered with brush and about two inches of soil.

Guide to Steel Septic Tank Maintenance and Repair

Photo of a steel septic tank cover near a home in the U.S.

Keep surface and roof runoff away from steel septic tanks or any other septic tanks and also from other septic system components like D-boxes and drainfields.

Flooding the system with uninvited water risks shortening the drainfield life and leads to septic system failure.

In the photo at left the steel septic tank is not only located too close to the house (typical for the era of its installation in the 1960's), but also it is near a roof drainage downspout.

The owner has wisely added an extension to redirect downspout spillage away from this tank.

Special Hazard Warning for Steel Septic Tank Covers

Collapsing home  made septic tank with steel components © D Friedman at

Watch out: Rusting steel tank covers can cause death! Rusted covers can collapse. We have reports of children and adults who have died from this hazard, as recently as December 1997. In 2000 the author consulted in a fatality involving an adult falling into a cesspool.

At a building inspection the author, even though walking carefully, stepped through a hidden, rusted-through steel septic tank cover (shown in the photos above on this page).

At left we're not sure what the heck we've got. This may be a steel septic tank that has collapsed, or a steel access riser to a home-made (out of stones) cesspool. This system was located less than 15 feet from a lake and cannot be working acceptably. And there was no safe cover.

Falling into a septic tank, drywell, or cesspool is quickly fatal, either from being buried by falling soils and debris, or by asphyxiation. Septic gases are highly toxic and can kill in just minutes of exposure. Even leaning over an empty (just pumped) tank has led to collapse and fatality of a septic pumper.

Special Problem with Rusted Off Baffles in Steel Septic Tanks - repair may be possible

Steel septic tank with lost cover (C) Daniel Friedman

Steel septic tank baffle problems: on a steel septic tank the inlet and outlet baffles often rust out and fall off before the owner realizes that the tank needs repair or replacement.

The baffle in this septic tank (photo at left) is on the right side of the manhole.

This damage permits solids to enter the soil absorption system. In the photo shown above on this page the steel septic tank baffle has rusted away at its top - visible in the lower left of the tank top opening.

Should we repair a steel septic tank that has lost its baffles?

If a steel septic tank is otherwise in good condition but its baffles have become damaged or have been lost entirely, try inserting a plastic tee in the inlet and outlet waste lines.

Septic tank baffles, or septic tank tees prevent solids from flowing out of the tank into the drainfield, or from blocking waste flow into the tank from the building it serves. But if you see that the steel septic tank baffles have been missing for some unknown time, perhaps a long time, especially at the tank outlet end, you can assume that this condition has reduced the future life of the drainfield by permitting solid waste to flow into that area of the septic system.

See Septic Tank Tees for more details about this septic system component.

Steel Septic Tank Bottom Rust-Out, Leaks, Abnormal Sewage Levels

Steel tank bottoms rust out permitting effluent to leak into soils around the tank, possibly giving a large void in tank at time of testing, thus subverting a loading or dye test. Since steel tank tops can be replaced while leaving the old tank in place, the condition of the top itself is not a reliable indicator of tank condition.

You may spot a leaky steel septic tank whose bottom or lower sides are gone by noticing that for a septic tank that is in use and has not just been pumped out, the level of sewage in the septic tank is lower than the outlet baffle or pipe. Details are at SEPTIC TANK LEVELS of SEWAGE.

This is a chapter of Septic Systems Inspection, Testing our free online class about septic system inspection procedures, defects in onsite waste disposal systems, septic tank problems, septic drainfield problems, checklists of system components and things to ask.

Also see The Septic Information Website our main page of articles and information about septic systems and onsite wastewater disposal systems inspection, testing, diagnosis, maintenance, and repair.


Continue reading at SEPTIC TANK BAFFLES or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see SEPTIC TANKS - home





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Publisher - Daniel Friedman