Skip to main content

Septic & Onsite Wastewater Systems

A septic system, also called an onsite wastewater system, is a way to treat and dispose of wastewater at a location where sewer service is not available. It typically consists of a septic tank and drainfield. 

Salt Lake County Health Department is responsible for reviewing and permitting new onsite wastewater system construction in Salt Lake County. We also inspect new systems to ensure they are installed to meet standards and will function properly to protect public and environmental health.

Onsite Wastewater Permitting Guidelines

We permit onsite wastewater systems for projects that have a daily flow of 5000 gallons or less of domestic wastewater (the wastewater from toilets, showers, bathtubs, laundry, and kitchens in homes, small businesses, and offices).

The Utah Department of Environmental Quality permits projects with a daily flow greater than 5000 gallons per day, or that include nondomestic wastewater flows such as agricultural or industrial processing or manufacturing.

Permitting Process

These steps will help you navigate the permitting process and determine if an onsite system is appropriate for your project:

Contact your city or municipality’s planning or zoning department to determine if there are land-use restrictions or other requirements associated with onsite wastewater systems.

Note that systems in certain areas must go through additional review, such as:

  • FCOZ for projects in the foothill canyon overlay zone.
  • Projects in the Salt Lake County watershed need a watershed construction letter from Salt Lake City Public Utilities, and onsite wastewater systems in watersheds have additional design requirements.
  • Projects in Drinking Water Source Protection zones need written approval from the drinking water system and are subject to additional design requirements according to the local drinking water source protection plan.

Contact the sewer district that serves your area and obtain a letter stating your project does not have sewer available or does not need to be connected to the public sewer.

Sewer connection is required if sewer is available within 300 feet of the property. 

Contact the public water system that will provide culinary water and obtain a water availability letter.

If water an individual water system with supply water, you will need to provide documentation of a water right, as well as show that the water systems meets the quality, quantity, and pressure standards in Salt Lake County Health Regulation #11: Individual Water Systems.

Site Feasibility

Not all sites are suitable for onsite wastewater systems.

Plans can be designed for a onsite wastewater system only once the following things are completed or determined:

  • soil exploration
  • hydraulic loading rate
  • slope
  • setbacks

Soil exploration is one of the first steps in determining if an onsite wastewater system can be installed on a property and is also important in sizing the system. An onsite wastewater professional certified by the Utah Division of Water Quality must conduct the soil exploration and design the system.

When contacting a certified onsite professional from the list above, please focus on contractors, consultants, and engineers. Government staff are also on the list but they are not able to do soil exploration or system design for projects within their jurisdiction due to conflicts of interest. Certified onsite professionals who are not government are not limited to the county under which they are listed.

Salt Lake County requires notification when soil exploration is conducted within its boundaries, and health department staff prefer to be present. Soil exploration should be done close to the proposed drainfield.

Soil exploration starts with digging a pit at least 10’ deep. If bedrock, unsuitable soil, or groundwater are encountered before 10 feet, the exploration stops. Soil exploration pits may be deeper depending on the proposed system design. Soil exploration is required to go at least 4’ below the proposed drainfield. For example, if a soil exploration pit is only 10’ deep, the max depth of the drainfield trench is 6’.

Soil layers in the exploration pit are then classified. Depending on the soil type, a classification can be used to determine the hydraulic loading rate (HLR) of the soil. Some soil types require further percolation testing to determine the HLR. Percolation testing takes longer and is more labor-intensive but gives a better determination of the HLR. The HLR is necessary in a formula with the estimated daily wastewater flow to determine the size of the drainfield.

Other factors, in addition to soil exploration, that must be considered during site feasibility includes slope and setbacks.

Slope is a limiting factor. Drainfields are not allowed on slopes above 35%. Slopes that are 25-35% need a slope stability study to ensure the slope will not fail when water is added.

Setbacks from property lines, utility lines, foundations, driveways, water courses, wells, springs, and other items of concern must be met. Reductions in setbacks may be granted with the use of an alternative system.

Plan Design

 An onsite wastewater professional certified by the Utah Division of Water Quality must conduct the soil exploration and design the system.

A level 2 onsite professional can design conventional systems.

If the project requires an alternative system, the onsite professional must be level 3.

Plans should include the design criteria outlined in R317-4-5

Application Submission

Once plans are ready, submit them to, along with the following items:

  1. Completed onsite wastewater construction permit application
  2. Soil exploration/percolation test results
  3. System design plans
  4. House/Building plans
  5. Water availability letter
  6. Sewer service letter (if within the jurisdiction of a sewer utility) 
  7. Watershed construction letter from Salt Lake City Public Utilities (if within the watershed) 

Once all necessary items are submitted and fees are paid, the application review will begin. Please allow 10 business days for review.

If the design does not meet code requirements or items are missing, we will provide comments and the applicant can respond and update the plans to meet code requirements or address deficiencies.

Approved applications will receive a permit, stamped copy of the approved plans, and  an approval letter.

Permits expire one year from the date of issuance, but extensions may be granted upon request.

Systems should be installed according to the approved plans. Any changes must be reviewed and approved by Salt Lake County Health Department. Systems must be inspected by the department prior to backfilling.

Alternative systems, pressure distribution, and holding tanks require operating permits to ensure they are properly maintained. These permits must be renewed yearly. Receiving an operating permit requires owners to show they are maintaining their systems appropriately.

Records of maintenance and servicing should be submitted to


Questions? Contact the Water Quality Bureau at or 385-468-3862.

Salt Lake County Health Department maintains a database of as-built diagrams of septic system installations. Request a copy of your as-built  diagram via our records request portal.

Here’s our plan review workbook for onsite wastewater.