Are Eggshells Good for Septic Systems?

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Septic systems play a crucial role in managing wastewater in many homes and properties that are not connected to a public sewage system. Proper maintenance of septic systems is essential to ensure their optimal functioning and longevity. One aspect that often sparks curiosity is the use of eggshells. This article will explore whether eggshells are good for septic systems, examining their composition, potential effects on the septic tank, and their biodegradability.

Are Eggshells Good For Septic Systems?

Septic systems rely on a delicate balance of natural processes to break down and treat wastewater. Homeowners often seek ways to enhance the performance of their septic systems and reduce the likelihood of clogs or malfunctions. One common question that arises is whether eggshells, with their high calcium carbonate content, can be beneficial for septic tanks.

Composition of Eggshells

Eggshells consist of approximately 94% calcium carbonate, making them predominantly composed of this compound. They also contain 1% magnesium carbonate, 1% calcium phosphate, and 4% organic matter. The outer shell has a thickness of 0.55 mm, while the inner eggshell is only 0.015 mm thick. The purpose of the dense outer shell is to protect the delicate egg inside.

The Role of Eggshells in Septic Systems

Eggshells, when introduced into a septic system, gradually degrade over time. As they break down, they release calcium carbonate, which increases the pH level of the septic tank. The increased alkalinity resulting from the release of calcium carbonate can have some potential effects on the septic system.

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Effect on pH Levels

The pH level of a septic tank is an essential factor for maintaining a healthy microbial environment. Typically, septic systems operate within a slightly acidic to neutral pH range. However, the addition of eggshells, with their alkaline nature, can cause the pH level to rise. This increase in pH negatively affects septic anaerobic bacteria, which are responsible for the breakdown of organic matter.

Impact on Septic Anaerobic Bacteria

Septic anaerobic bacteria thrive in an environment with specific pH conditions. When the pH becomes more alkaline due to the presence of eggshells, the activity and efficiency of these bacteria may decrease. This can potentially hinder the decomposition of solid waste and lead to a less effective septic system.

Biodegradability of Eggshells

While eggshells are biodegradable, they take a considerable amount of time to break down completely. Unlike organic matter that decomposes relatively quickly, eggshells may persist in the septic system for years rather than months. This slow degradation process makes them less ideal for rapid decomposition and may contribute to the accumulation of waste over time.

The Problem with Eggshell Membrane

Apart from the composition of eggshells, the thin membrane lining the inner surface can pose an issue in septic systems. The stringy nature of the eggshell membrane can lead to clogs and blockages within the septic tank or the drainage field. These obstructions can impede the flow of wastewater and compromise the overall efficiency of the septic system.

Are Eggshells Good For Septic Systems: FAQs

Putting vinegar in a septic system is generally considered safe and can even be beneficial. Vinegar is a mild acid that can help break down organic matter and control odors in the system. However, it’s important to use vinegar in moderation and with caution. Excessive amounts of vinegar can disrupt the natural balance of bacteria in the septic tank, leading to potential issues.

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Using Epsom salt in a septic tank is generally safe as it is pH neutral. Epsom salt, also known as magnesium sulfate, is unlikely to disrupt the natural balance of bacteria in the tank.

Adding baking soda to a septic tank can be beneficial in certain situations. Baking soda, also known as sodium bicarbonate, can help maintain a neutral pH level in the tank, which is important for the growth of beneficial bacteria. It can also help control odors.

There can be several reasons why your septic tank might emit a foul odor. One possibility is that the tank is due for maintenance and needs to be pumped. Over time, solid waste accumulates, causing the tank to become overloaded and release unpleasant odors. Another potential cause could be a damaged or faulty septic system component, such as a cracked tank or broken pipe, allowing gases to escape. Additionally, excessive water usage, improper waste disposal, or a clogged drain field can contribute to the odor. Regular maintenance and proper care are crucial to prevent septic tank odor issues.

A septic distribution box may become full of water due to various reasons. It could be a sign of a clog or malfunction within the system, leading to improper drainage and potential issues.


In conclusion, while eggshells are composed mainly of calcium carbonate and have biodegradable properties, they are not recommended for septic systems. The release of calcium carbonate as eggshells degrade increases the pH level of the septic tank, negatively impacting the septic anaerobic bacteria responsible for waste decomposition. Additionally, the slow degradation process and the potential for eggshell membrane clogs make them less suitable for septic systems.

Considering the delicate balance required for optimal septic system performance, it is best to avoid introducing eggshells into the system. Instead, homeowners should focus on proper maintenance, regular pumping, and avoiding the disposal of harmful substances or non-biodegradable materials into the septic system.