How Much Does It Cost to Install a Septic System Filter?

By Michael Franco

March 12, 2025

Septic tank filters play a crucial role in keeping your septic system functioning efficiently. If you own a property with a septic system or are planning to install one, understanding how these filters work and their importance is essential.

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What Is a Septic Tank Filter and How Does It Work?

A septic tank filter is a specialized device installed in the outlet baffle of a septic tank. Its primary function is to prevent solid waste from leaving the tank and entering the drain field, where it could cause blockages or system failure. The filter typically consists of a cylindrical plastic cartridge with small slots or mesh that trap solids while allowing treated wastewater to flow through.

As wastewater flows through the septic tank, heavier solids settle at the bottom, forming sludge, while lighter materials, such as grease, float to the top. The filtered water that exits the septic tank should be relatively free of solids, which helps maintain the longevity and efficiency of the drain field.

Do You Need a Septic System Filter?

Whether septic tank filters are necessary depends on your perspective and local regulations. From a maintenance standpoint, filters are highly beneficial because they significantly reduce the risk of clogs in the drain field, which is one of the most expensive parts of a septic system to repair or replace.

Is a Septic System Effluent Filter Required by Law?

In terms of legal requirements, many local and state building codes now mandate the installation of septic tank filters in new systems to improve overall performance and environmental safety. Even if not legally required in your area, installing a filter is a wise investment to extend the life of your system and minimize costly repairs.

How Do I Know If My Septic Tank Has a Filter?

To determine whether your septic tank has a filter, you’ll need to locate and inspect the outlet baffle. If you don't feel comfortable inspecting the tank yourself, you can hire a professional septic service provider to check for you.

Here’s how to check yourself:

Step 1: Find the Septic Tank Lid

The lid is usually buried just below the ground surface. Use a shovel to carefully uncover it.

Step 2: Open the Lid

Use a pry bar to lift the lid off and move it to one side. Once you have access to the tank, look for the outlet baffle, which is located where the effluent exits the tank.

Step 3: Check for a Filter

If there is a filter present, you should see a cylindrical cartridge inserted into the outlet baffle.

Septic System Filter Installation Costs

Septic tank filters can be installed on existing systems. Retrofitting a filter involves adding one inside the outlet baffle of your septic tank. This process requires opening the septic tank lid to access the baffle where the filter will be inserted.

While the initial installation cost of adding an effluent filter to your septic system might seem like a significant upfront expense, the long-term benefits of protecting your drain field and avoiding costly repairs make it a worthwhile investment.

The cost of professional installation of a septic tank filter on an existing system can vary depending on several factors, including:

Labor Costs

Professional septic filter installation typically ranges from $275 to $850, depending on local rates and the complexity of the job.

If the outlet baffle needs modifications or repairs, additional costs may be incurred.

Filter Cleaning Price

Cleaning an already installed septic tank filter usually costs about $150.

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Installing a Septic Tank Filter on an Existing Septic System

This job is best handled by a professional to ensure proper installation and compliance with local regulations. Here’s a general overview of how a filter can be added to your existing system:

Step 1: Locate the Septic Tank Lid

Find the septic tank lid, which is typically buried a few inches below the surface.

Step 2: Open the Septic Tank Lid

Using a long-handled screwdriver or pry bar, carefully open the lid, taking precautions to avoid harmful gases.

Step 3: Find the Outlet Baffle

Inside the tank, locate the outlet baffle where wastewater exits.

Step 4: Insert the Filter

Carefully insert the filter cartridge into the outlet baffle according to the manufacturer’s instructions, ensuring it is seated securely.

Step 5: Close the Septic Tank Lid

Once the filter is properly installed, close the septic tank lid and ensure it is securely in place.

Final Thoughts

While not always legally required, septic tank filters offer clear advantages in terms of extending system life and preventing drain field issues. If you’re unsure whether your system has a filter or you want to install one, consulting a professional is always a good idea. With proper maintenance and the right upgrades, your septic system can serve your household reliably for many years.

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