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The majority of your septic system is buried underground. Since it is out of sight, many homeowners don’t pay attention to their waste removal. But whether you are planning a septic installation for new construction or you suspect an issue with your property’s drainage, you should familiarize yourself with your system’s features.


What Is a Septic Distribution Box?

A septic tank’s distribution box (or D-box) is a container (typically concrete) that receives the septic tank effluent and re-distributes it into the network of attached drain fields and pipes. To put it simply, its job is to evenly distribute the wastewater into the leach field.


How Does it Work?

The distribution box of the septic tank system is used to evenly distribute the wastewater from the septic system to the dispersal field. As a junction of various pipes, the D-Box connects to the septic tank as well as absorption elements, such as the drain field leach lines.

Like most of your septic system, the distribution box uses gravity. Liquid waste known flows into the box through one pipe and is divided evenly to exit through the drain system. Since the leach field and box are located below the septic tank, the wastewater moves downhill as it enters the container. Additionally, the box has several holes with rotating devices. The devices control the wastewater flowing outward, ensuring an even amount enters each area of the leach field.

A working, reliable septic system relies on this function. If your distribution box is unable to evenly re-distribute wastewater, the liquid will accumulate in one section of your leach field. This can overwhelm the area, compromising the overall efficiency of the field. Over time, the distribution box can erode and will need to be replaced.


How Do I Find My Septic Tank Distribution Box?

  • The location of the distribution box depends mostly on space and layout of the septic’s drain field.
  • If your layout consists of a rectangular and level drain site, your distribution box is likely to be located near the edge of the drain field, closest to the septic tank.
  • You can also look for a depression in the ground between the septic tank and drain field a couple of feet in diameter.

While a D-box does not need to be pumped regularly like your septic tank, it should be inspected to make sure it is in proper working condition. Inspections help to ensure that your system is working properly before major issues occur or warning signs are presented. By being proactive, you can make minor adjustments or repairs as needed to hopefully prevent unnecessary large issues, failures, or backups.

A concrete D-box can typically last up to 20 years. However, in the event of sludge buildup, tree root invasions, improper maintenance, heavy machinery on top of the box or other issues that can cause unrepairable damage to your distribution box, you may need to replace it.

Some important inspection points of your distribution box are:

  1. Outlets & Openings – Most well-designed systems will allow for the outlet openings to be adjusted to regulate the flow if necessary.
  2. Uneven Distribution – If a D-box has tilted or tipped, this could result in distribution to only one section of leach fields, which could result in overflow of effluent to the surface, or a system backup or clog.
  3. Interior – The interior of your distribution box can indicate some issues with your system (past or present), like flood lines.



If you notice flooding in one part of your drainfield, take note. Your distribution box is likely broken or blocked—and needs to be repaired or replaced.

This can happen due to several reasons, including:

  • Natural wear and tear
  • Sludge accumulation
  • Improper septic system care
  • Invading tree roots
  • Driving heavy machinery over the box
  • Flooding and other inclement weather conditions

The pipes leading to or from the box can also become clogged or damaged. Similarly, the rotating devices connected to the openings may fail, resulting in uneven liquid distribution.


How Can You Keep Your Distribution Box Functioning?

Proper installation is an important aspect of a properly functioning distribution box. It should be completely level and placed no more than a foot below the ground. The system should also be installed based on the manufacturing specifications of the septic tank, whether that calls for a fiberglass, plastic, or concrete junction box.

Routine septic pumping and inspections can help your distribution box function properly. Professionals can inspect the box to make sure wastewater is flowing through the drain field evenly.

If any signs of damage occur, such as crumbling walls, flooding, or leaks, do not wait to have a replacement installed. Addressing distribution box issues promptly could safeguard your property and septic system against damage such as flooding.


Call West Coast Sanitation Today!

At West Coast Sanitation, we know that you do not have time to deal with septic problems. One of the ways you can maintain this balance and keep your septic system working like it should is to have your tank pumped regularly. Please give us a call at (951) 780-5922 right away. We have professionals ready to answer your questions and get your system working properly again.