Septic Systems

An on-site wastewater treatment and disposal system – known commonly as a septic system – is a wastewater treatment facility located within an individual property boundary that collects, treats and disposes of wastewater from a home or business. This is different from a central or municipal wastewater treatment facility which receives wastewater from other locations for treatment.

A septic system can consist of several components: a septic tank, a distribution box, a dosing chamber and a drainfield. Proper maintenance will ensure that a system functions the way it was designed to work and will prolong the lifecycle of the system.

The septic tank collects and partially treats household wastewater. It separates liquids and solids and begins the bacterial breakdown of waste into liquids and gas. The gas is vented away. The liquids pass into the drainfield where they are slowly absorbed into the ground, where more bacterial breakdown takes place, clay particles trap nutrients, and other pollutants are filtered away.

On-site wastewater treatment and disposal systems are governed by Delaware’s Regulations Governing the Design, Installation and Operation of On-Site Wastewater Treatment and Disposal Systems (7 DE Admin. Code 7101). The regulations are also available as a PDF Version with Exhibits and Attachments.

Septic System Approval

Getting a septic system approved in Delaware is a three-step process. Each step will involve a licensed professional who will work with the applicant and the Department and submit application materials and fees as needed.

Site Evaluation

Have a site evaluation performed by a licensed Class D soil scientist to determine what type of disposal system, under current regulations, can be sited on the parcel. The soil scientist performs field work, prepares a site evaluation report and submits it to the Department for approval.

System Design

Hire a licensed system designer to design the septic system and obtain a permit. For gravity-based systems, use a Class B designer. For engineered or pressure-dosed systems, use a Class C designer.


Septic systems are installed by licensed Class E system contractors.

Types of Systems

The Groundwater Discharges Section maintains a list of approved septic system products and lists approved innovative and alternative systems that might be used where site constraints limit the ability to install conventional wastewater treatment systems.

State Financial Assistance

The Septic Rehabilitation Grant Program provides funding to replace failing septic systems and cesspools with on-site wastewater disposal systems that will function in an environmentally sound and cost-effective manner. The program also provides funding for costs associated with connecting to central sewer systems.

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