Septic Systems

An on-site wastewater treatment and disposal system – known commonly as a septic system – is a wastewater treatment facility located within your property boundaries that collects, treats and disposes of wastewater from your 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. Learn More.

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.

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.

Managing Your Septic System

Saving water can save you problems, and money. The smaller the amount of wastewater you put through your system, the longer the system will last. Take shorter showers and use a low-flow shower head. Use faucet aerators in the kitchen and bathroom sinks. Use your dishwasher and washing machine sparingly. Install low-flush toilets in your bathroom.

Use biodegradable toilet paper. Many products are labeled “approved for septic tank use.” Never dispose of coffee grounds, sanitary napkins, tampons, condoms, cigarette butts, or disposable diapers in the toilet or sink. Never pour grease, paints, caustic or oily liquids, fuels, cooking fats or motor oils into sinks or toilets.

Keep your system’s drain field clear and intact. Don’t build anything on it. Don’t drive anything on it. Don’t plant any deep-rooted trees or shrubs within 10 feet of your disposal system.

Have your septic tank pumped by a licensed Class F liquid waste hauler at least every 3 years. Never climb into a septic tank yourself. Methane and hydrogen sulfide gases, which are present from the decomposition processes, may cause illness or death.

Record-Keeping is Important

Knowing the location of your septic system is important for managing maintenance, repairs, and protecting the system. Keep all the information about your system in the same place. Your records should include:

  • Copies of all permits and correspondence about the system
  • A map or drawing of the system
  • Detailed records of all maintenance, inspections or repairs
  • Receipts and records of all pumping of your system

Watching for Problems

A malfunctioning or failed septic system is a nuisance for you. It is also a public health hazard. Repairing or replacing a problem system will protect your family, friends and drinking water.

Here are some warning signs to watch for:

In the House

Slowly draining sinks and toilets
Plumbing backups
Gurgling in the plumbing

In the Yard

Damp soil or ponding over the system
Grass growing faster and greener
Sewage odor near the system

If you you have a problem with your disposal system or suspect it may be failing, contact a licensed Class E system contractor or a licensed Class H system inspector for help.

If you have any questions, contact the Groundwater Discharges Section at 302-739-9947 (in Dover) or 302-856-4561 (in Georgetown).

State Financial Assistance

The Septic Rehabilitation Loan Program provides low-interest financing 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 new septic construction and costs associated with connecting to central sewer systems.