Putting Dead Animals in Septic Tanks—A Hack or Hoax?

If you are a septic system owner, you probably have heard the supposed hack of throwing a dead cat or chicken into the septic tank.

 Some homeowners swear by this hack, and some even claim they have used it for decades.

It is not clear where or when the phenomenon started, but the practice is believed to be as old as septic systems.

Back in the day, putting a dead animal in a new septic tank was common practice to jumpstart it by introducing bacteria.  

It was believed that dead animals aids the decomposition of solids in septic systems because they add more or unique bacteria that are effective in breaking down solid waste.

This old practice mutated over the years, from using the carcass in new systems to adding dead animals as a maintenance practice.

But what are the merits of this practice? Does it really work, or is it just a hoax that has taken a life of its own over the years?

The Short Answer:

See, every time you flush waste (from your toilet, dishwasher, baths, shower, washing machine, etc) into your septic tank, you are essentially introducing a fresh infusion of beneficial bacteria into your septic system.

So, the waste that you release into your septic system is just enough to generate the needed bacteria for your septic tank to work effectively.  

In other words, bacteria from a dead animal won’t provide anything essential to your septic system that’s not already coming from the usual sources.

Reasons Not to Put Dead Animals in Septic Tank (aka The Long Answer)

Here are some reasons why using a carcass in your septic tank is a bad idea:

Animals Break Down Differently

Human waste contains a uniform mix of organic matter that can easily decompose under anaerobic conditions.

Dead animals, on the other hand, are composed of a much more diverse range of organic matter, including bones, connective tissue, and other less digestible materials.

These materials are more difficult for the microorganisms in septic systems to break down.

 As such, adding a dead animal to the septic tank may result in the tank filling up sooner than usual.

The bones and fur of dead animals may also take too long to break down.

Apart from contributing to the septic tank waste buildup, they also cause a pumping challenge.

The bones may clog up the pipes and damage the machinery of the pumpers.

So, in a nutshell, adding a dead animal to your septic tank will cost you more money because you will need more pumping, and you may also spend more money on repairs.

Introduction of the Wrong Bacteria

As we have already established, the main reason why dead animals were thought to benefit septic systems is the introduction of bacteria.

This is why it was common practice to use dead animals in new systems.

However, septic system experts have studied the microbiology of septic tanks and discovered that adding dead animals does not add helpful bacteria in the tank.

While it is true that the dead animal will add millions of bacteria, the bacteria needed in the septic tank are of a different strain.

The septic tank relies on anaerobic bacteria to break down the waste.

(Anaerobic bacteria are a special kind of bacteria that thrive in the absence of oxygen and are, therefore, perfect for septic systems).

However, studies show that decomposing bodies usually have aerobic bacteria (e.g. Proteo bacteria).

Adding aerobic bacteria in the septic tank is counterproductive because they will not survive in the anaerobic conditions.

Furthermore, they may also kill the helpful bacteria and thereby make the problem worse.

Anaerobic bacteria are abundant in the human gut and are passed into the septic system each time you flush fecal waste in the toilet.

So, even if it’s a new system, just start using it, and the bacteria population will grow naturally with each flush of the toilet.

It Alters the Septic Tank Chemistry

Adding a dead animal to the septic tank will alter the tank’s chemistry.

A septic tank has a unique chemistry that helps ensure the efficiency of the system.

For starters, the microbes that help in breaking down of the waste need the pH of the tank to be just right.

In addition to the pH, the microbes need the right temperature as well as the right nutrients for them to thrive.

Messing up with the chemistry of the tank will deal a blow to the efficacy of the helpful bacteria.

When the bacteria are unable to continue with their biological processes, the tank will fill up pretty quickly.

A fast buildup of organic matter will not only result in sewage backup in the plumbing system but also clogs and blockages in the system.

Failure to remedy such a situation will lead to contamination of the groundwater as more bacteria-laden filth will be sent from your over-burdened septic tank system into the leaching field.

Additionally, the chemistry of the septic tank can impact the quality of the effluent that is discharged from the tank.

If the effluent contains high levels of pathogens, it can pose a risk to human health and the environment.

Therefore, it is essential to maintain proper septic tank chemistry by only allowing human waste into the tank.

Any other waste, including dead animals, should be disposed of in a different way.

To Sum It Up…

 Forget what you have heard from the grapevine – adding a dead possum, cat, or chicken to your septic tank will do you more harm than good.

The bacteria in human waste should be sufficient to keep the septic system running.

Granted, there are some situations where you may need to boost the population, but you should do that using biological additives.

Always remember that not all bacteria work the same way.

Your septic tank needs anaerobic bacteria which are adapted for the toxic and low-oxygen environment in the septic tank.

Adding aerobic bacteria to the system will, therefore, not do any good.