Concrete Septic Tank Corrosion

This post may contain affiliate links. This means I will make a commission at no extra cost to you should you click through and make a purchase. Read the Affiliate Disclaimer and Privacy Policy.


Don’t let corrosion ruin your septic system. Find out the common causes of concrete septic tank corrosion and how to combat it.

Concrete septic tanks are a common component of many home septic systems. However, these tanks are not immune to corrosion, which can lead to structural damage and leaks. Corrosion can occur in a number of ways, including:

Concrete Septic Tank Corrosion: Sulfuric Acid

One of the main causes of concrete septic tank corrosion is the presence of sulfuric acid. This acid is commonly found in septic tank waste and can cause corrosion of the tank’s concrete walls and floor. The acid also corrodes the tank’s metal components, such as the inlet and outlet pipes.

This type of corrosion, also known as Microbial Induced Corrosion (MIC). It is a common problem that can cause significant damage to septic systems. MIC occurs in a three-step process, beginning with a reduction in the pH of the septic tank`s concrete walls. This is caused by the mildly acidic nature of hydrogen sulphide gas, a by-product of the anaerobic bacterial decomposition of organic matter in the septic tank. This leads to the growth of a new strain of bacteria called Thiobacillus, which eats hydrogen sulphide gas and produces sulfuric acid as a by-product. Sulfuric acid is highly corrosive to concrete.

Acidic Soil

Another cause of corrosion in concrete septic tanks is installing the tank in acidic soil. The acidity of the soil can cause the concrete to break down over time, leading to cracks and leaks in the tank. It is important to consider the pH of the soil when installing a concrete septic tank to avoid corrosion and prolong the life of the system.

Related Post  How To Repair A Cracked Concrete Septic Tank

Concrete Septic Tank Corrosion: Water Softeners

Water softeners can also contribute to corrosion in concrete septic systems. The salt used in water softeners can also cause the concrete to deteriorate, leading to structural damage and leaks in the tank.

What Are The Effects?

Concrete septic corrosion can have several effects on a septic system, including:

  • Damage to the concrete tank: The concrete tank of a septic system can become weakened or cracked due to corrosion, which can lead to leaks and damage to other parts of the system.
  • Blockages in the drain field: Corrosion can also cause blockages in the drain field, preventing proper drainage and potentially leading to backups in the system.
  • Reduced efficiency: As the system becomes corroded, it may not function as efficiently as it should, leading to increased maintenance and repair costs.
  • Environmental hazards: Leaks or backups in the system can lead to environmental hazards, such as contamination of groundwater or surface water.

In severe cases, concrete septic corrosion may require the entire system to be replaced. Regular maintenance and inspection can help to prevent or minimize the effects of corrosion.

Concrete Septic Tank Corrosion: Prevention

While concrete septic tanks are durable and long-lasting, they are not immune to corrosion. However, by understanding the causes of corrosion and taking steps to prevent it, homeowners can help to ensure that their septic tanks remain in good condition for many years.

Fight Corrosion By:

  1. Installing septic air tank vents or ensuring that existing vents are not blocked is crucial in preventing the accumulation of hydrogen sulphide gas in the septic system. Septic air vents allow for the free movement of gases out of the system, reducing the risk of buildup and promoting proper functioning of the septic system. It’s important to make sure that the air vents are not blocked by debris, foliage or other materials to ensure proper ventilation.
  2. Regularly pumping the septic tank.
  3. Conducting a soil analysis before installing a septic system.
  4. Using Potassium Chloride as the regeneration salt for water softeners is an effective way to prevent corrosion in the septic system. Potassium Chloride is a non-corrosive alternative to traditional sodium chloride (salt) used in water softeners, and it does not contribute to the buildup of salt in the septic system. Additionally, avoiding the use of water softeners for outdoor use such as gardening can also help to reduce the load on the septic system, and minimize the risk of corrosion. It’s also important to regularly maintain the water softener, as a malfunctioning unit can lead to overuse of salt, which can damage the septic system and promote corrosion.
  5. Use concrete that is resistant to corrosion. You can obtain this by using specialized concrete mixes that are designed to resist corrosion, or by adding a chemical admixture to the concrete during the curing process. Chemical admixtures are added to the concrete mix to enhance its properties, such as workability, durability, and corrosion resistance.
  6. Regularly inspect and maintain any metal components in the septic system, such as pipes and tanks, to ensure they are not corroding.
  7. Use non-corrosive cleaning products in the household to avoid damage to the septic system.
Related Post  Why Do Concrete Septic Tanks Fail?

Final Thoughts

In summary, concrete septic tanks are a durable and reliable component of many septic systems. However, they are not immune to corrosion, which can be caused by factors such as microbial induced corrosion, acidic soil, and water softeners. The effects of corrosion can range from minor to severe, and in some cases, the entire septic system may need to be replaced. Regular maintenance and monitoring of the septic system is also important to ensure that corrosion is identified and addressed in a timely manner.