What is Septic Design?
- kiarastamand21
- May 8
- 6 min read
A Complete Guide for Builders, Agents, and Homeowners.
When constructing or purchasing a home not on a municipal sewer system, there's one critical element that tends to get forgotten until it's a bit late in the building game: the septic system. And at the center of a working, code-compliant septic system( whether it is Glendale Arizona, Paradise Valley, or any of the surrounding areas) is one essential element if you'd like to be able to use the restroom in your house. That would be the septic design.
Whether you're a builder preparing to turn dirt on a new construction, a real estate professional helping a client close on a house, or a homeowner preparing to construct your dream home, septic design is something you should know to avoid costly delays, failed inspections, and even legal issues. Here, we'll do our best to explain what septic design is, why it matters, and what you should know in order to do it right.
What is Septic Design?
Septic design is the process of designing, sizing, and siting an on-site wastewater treatment system (also referred to as a septic system) to discharge sewage from a building or a home where there is no available public sewer line.
An effective septic design ensures that:
Wastewater is properly treated and distributed safely,
The system is state and local building codes compliant,
It provides for the number of bedrooms (and planned water use),
It's suitable to the topography and soil of the property.
Septic design is not a matter of selecting a tank and a drainfield. It's a technical, regulatory, and environmental process that involves:
Soil testing (also known as perc tests or soil evaluation),
Determining system type (conventional or alternative),
Mapping system components on the site plan,
Sizing the system based on estimated use,
Submitting in plans for permitting.
Why Septic Design is a Big Deal
Septic design isn't just about efficiency—it's about protecting an investment in real estate.
1. It Prevents System Collapse
A faulty septic system can cause sewage to back up, clog the system, or taint the environment. That means tens of thousands of dollars in repair, property loss, and even potential legal culpability.
2. It's Required
Counties and municipalities require an approved septic plan before construction or system installation. Without approved plans, you cannot receive a building permit, let alone a certificate of occupancy.
3. It Impacts Home Value
When a home has septic issues—or no permitted system—real estate deals fall through. A good septic plan gives peace of mind, and in most cases, gives resale value.
The Septic Design Process (Step-by-Step)
Here's a general overview of what's typically involved in the septic design process:
Step 1: Site Evaluation
The site visit initiates the process of assessing the land. A septic designer will go over:
Lot size and shape
Land slope
Where wells, structures, and property lines are located
Drainage- This enables the system to be installed in an area with adequate setbacks and no environmental issues.
Step 2: Soil Testing
This is the most critical phase of the design process. The designer performs:
Standard Site and Soils Testing, there is no limiting layers which means you will be able to quickly see how the liquid will percolate through the soil
Site Specific Soils Testing- this is when the designer hits a limiting layer therefore you must run a site specific percolation test in three areas on the property to actually see how quickly the affluent will behave in the soil if its too rocky or sandy
Seepage Pit Performance Testing- if the leach field is to be seepage pit, a seepage pit performance test is required by Maricopa County and Pinal County in Arizona to see how the seepage pit will behave as a drain field.
Different soils such as clay, loam, sand, allow for different drainage. The test results determine if a standard system will suffice or an alternative system is needed.
Step 3: System Sizing
The system is sized based on the home's expected water usage, typically based on the number of bedrooms. More bedrooms = more wastewater = larger system.
Designers use county or ADEQ (Arizona Department of Environmental Quality) standards to decide:
Septic tank size
Size and arrangement of the leach field (or other system)
Step 4: Creating the Layout
Once sizing is finished, the designer creates a detailed site plan showing:
Location of septic tank
Location of drain field or disposal area
Setbacks to wells, property lines, and structures
Elevation data and slopes
If required, it will also include a reserve area, a second site on the property that can be used in the future if the primary drainfield is a failure.
Step 5: Permit Submission
The whole design, soil survey, and site plan are submitted to the local health agency or environmental department for approval and permitting. In Arizona, for example, septic permits are controlled by local counties and coordinated with ADEQ.
Step 6: Installation
Once the permit has been approved, a licensed contractor (like BEST Septic Solutions) installs the system exactly as specified in the approved design.
After installation, the system is inspected and must be given final approval before it can be utilized.
Design Types of Septic Systems
There is no single "one-size-fits-all" septic design. Depending on soil, slope, and space constraint, a designer may choose one of several different types of systems.
1. Conventional Gravity System
Most appropriate for ground with good drainage and properties that have enough drop in elevation. Wastewater flows from the home to the septic tank and on to a drain field.
2. Pressure Distribution System
Used where soil is poor or the layout demands more even spreading. Effluent is distributed under pressure by a pump to avoid overloading one section of the field.
3. Aerobic Treatment Unit (ATU)
The systems bring oxygen into wastewater to enable it to break down faster. Common in areas with poor soils or no space.
4. Drip Distribution or Low-Pressure Pipe (LPP)
Used on sloping or problematic ground. Effluent is distributed slowly over time, reducing environmental impact.
Common Septic Design Mistakes (and How to Steer Clear of Them)
Being a septic company that's come in to fix more tardy permits or failed systems than we can count, we've witnessed it all. Here are some common mistakes we help our clients avoid:
Starting Any Building Without A Site and Soils Test - County will require this to be done.
Starting Any Building Without the Permit Process Being Started- Maricopa and Pinal County will require this prior to issuing a building permit in
Designing Without a Soil Test - Assuming system type without conducting a soil test is a guaranteed recipe for disaster. We always need good testing before design.
Under-Sizing the System -Trying to cut costs by designing a smaller, or cheaper, system means overloads and failures. Or a complete replacement in the near future It's not worth it.
Insufficient Drain field Placement -Installing a drain field in a low area or slow-draining location can lead to backups and ponding. We plan according to site conditions working closely with the G & D engineer.
Leaving Out the Reserve Area- For the event that the primary drain field fails, a reserve area saves the property from needing to be completely redesigned or having expensive repairs.
Who Needs Septic Design
If you find yourself in any of the following situations, septic design must be at the forefront of your mind:
Building a new home on land with no sewer hook-up
Buying vacant land to build on in the future
Rebuilding a failed system
Adding bedrooms or a guest house and expanding
Dividing land into several lots in Arizona
At BEST Septic Solutions, we work with homeowners, real estate agents, builders, architects, and land developers every day to make septic design not a speed bump in your project.
How BEST Septic Solutions Can Assist in Arizona
Septic design can be a headache, but it does not have to be. When you work with BEST Septic Solutions, you get:
Professional soil testing and design assistance
Rapid permitting of plans
Customized systems by your project and property needs
Seamless coordination from design to installation
Prompt response to appropriate parties including builders, engineers, and county officials
We know what is required to have your design permitted and installed punctually and stress-free.
Final Thoughts
Septic design is the foundation of a safe, functional, and legally compliant septic system. Whether you’re building your first custom home, managing a real estate transaction, or developing rural land, don’t leave this step to chance.
Want to get septic design done right from the start? Call BEST Septic Solutions. In Arizona, we handle the soil testing, design, permitting, and installation so that you can focus on construction and selling with ease.
