Septic Systems 101: Everything You Need to Know Before You Build in Arizona
Building on property without access to a public sewer? You may need an onsite wastewater system, commonly called a septic system. Before construction begins, the property must be evaluated to determine whether it can support the proposed development and what type of system may be required. This guide explains how Arizona septic systems work, what the permitting process involves, and what to consider before you buy, design, or build.
Septic planning isn’t something to leave until the building plans are finished. Whether a property can support an onsite wastewater system may affect where you can build, what you can build, and how the entire site must be arranged.
Soil conditions, slope, available space, expected water use, required setbacks, and other site constraints can all influence the type, size, and location of the system. Even a large parcel may not have enough suitable space once buildings, wells, property lines, easements, washes, and reserve-area requirements are considered.
Arizona regulates septic systems to protect public health and groundwater. The Arizona Department of Environmental Quality, commonly called ADEQ, establishes statewide requirements, while most applications are submitted to the county where the property is located.
The exact requirements can vary based on the property, county, proposed development, expected wastewater flow, and type of system needed. Understanding the process early can help you avoid buying an unsuitable property, redesigning a site plan, or delaying construction.
What Is a Septic System?
A septic system is an onsite wastewater treatment system that collects, treats, and disperses wastewater on the property rather than sending it to a municipal sewer.
Wastewater travels from the building through underground plumbing and into a septic tank. Inside the tank, solids settle to the bottom while oils and other lighter materials rise to the top. The liquid wastewater then moves through distribution components into a disposal or dispersal area.
The septic tank is only one part of the treatment process. The disposal area and the soil beneath it provide additional treatment as wastewater moves through the ground. A properly planned site must also include a reserve area that can support a replacement disposal area if the original one can no longer be used.
The basic parts of a septic system include:
Plumbing from the building
Septic tank
Distribution components
Disposal or dispersal area
Reserve area
Soil beneath the system
Each component has a specific job. A septic system can’t function properly through the tank alone. The soil, disposal area, and available reserve space are all essential to how the system is designed and approved.
How Does a Septic System Work?
A septic system treats wastewater in several stages:
Wastewater leaves the building.
Water from toilets, sinks, showers, and other plumbing fixtures flows through a pipe into the septic tank.Materials separate inside the tank.
Heavy solids settle to the bottom, while oils, grease, and other lighter materials rise to the top.Partially treated wastewater exits the tank.
The liquid between these layers, called effluent, flows out through the system’s outlet.Effluent enters the disposal area.
Distribution components spread the effluent through the approved disposal or dispersal area.The soil provides additional treatment.
As the effluent moves through the soil, natural physical and biological processes remove additional contaminants before the water reaches the surrounding environment.
The tank handles only the first stage of treatment. The disposal area and the soil beneath it are essential parts of the system.
Wastewater leaves the building.
Solids settle while liquids continue through the system.
Effluent is distributed across the disposal area.
The soil provides additional treatment.
The septic tank is only the first stage of treatment. The disposal area and the soil beneath it are essential parts of the system.
Who Regulates Septic Systems in Arizona?
The Arizona Department of Environmental Quality (ADEQ) establishes the statewide rules for onsite wastewater systems. In most cases, septic applications are submitted to the county where the property is located.
Counties administer their onsite wastewater programs through delegation agreements with ADEQ. However, larger, more complex, or specialized projects may require direct ADEQ review. Property owners may also need to meet separate planning, zoning, floodplain, well, and building requirements.
There isn’t one identical septic application process for every Arizona property. The responsible agency and required documents depend on the property’s location, proposed use, wastewater flow, and system type. Confirm the current requirements with the applicable county or regulatory agency before beginning the design or application process.
For statewide information, visit ADEQ’s Onsite Wastewater Treatment Facilities page.
Do You Need a Septic System?
A property generally needs a septic system when it can’t connect to a public sewer. This is common for rural properties, undeveloped parcels, and land located outside a city or utility provider’s sewer service area.
A septic system may be needed when:
No public sewer is available
The property is outside a municipal service area
A sewer connection isn’t physically or financially feasible
A rural or undeveloped parcel is being prepared for construction
Don’t assume that a lack of nearby sewer service automatically means septic will be approved. First, confirm sewer availability with the applicable municipality or utility provider. If sewer connection is required or reasonably available, the property may not qualify for a septic system.
If sewer isn’t available, the property must still be evaluated to determine whether it has suitable soil, adequate space, and an acceptable location for an onsite wastewater system.
What Should You Know Before Buying Land?
Before buying land in Arizona, find out whether the property can support the home or development you’re planning. Septic feasibility can affect the building location, site layout, project cost, and even whether the proposed use is practical.
Start by checking:
Whether public sewer service is available or required
Whether the parcel has a previous septic approval
Whether an existing septic system was properly permitted
Soil and site conditions
Lot size and usable area
Slope, drainage, washes, and floodplain constraints
Existing or proposed wells and water infrastructure
Easements and confirmed property lines
The proposed home size and expected wastewater flow
Space for both the primary and reserve disposal areas
Plans for future additions, guest houses, workshops, or commercial uses
Previous septic approval can provide useful information, but it may not cover your proposed project. An existing system may also need to be evaluated to confirm its permitted capacity, condition, and compatibility with the planned use.
Future plans matter too. Adding bedrooms, constructing a guest house, or converting part of the property to commercial use can increase wastewater flow and change the system requirements. It’s best to account for these plans before deciding where to place the home, driveway, well, and other improvements.
A large parcel doesn’t automatically mean there’s enough suitable space for a septic system. Steep terrain, poor soil, setbacks, easements, washes, and other constraints can reduce the area available for both the primary system and required reserve area.
What Is a Soil and Site Investigation?
A soil and site investigation evaluates whether a property can support an onsite wastewater system and provides the information needed to select and design an appropriate system.
During the investigation, a qualified professional evaluates the soil and the physical features of the property. This may include:
Soil texture and structure
Restrictive soil conditions
Findings from test pits or other excavations
Depth to groundwater, bedrock, or other limiting conditions
Slope and topography
Available installation area
Required setbacks
Proposed development and expected wastewater flow
Potential locations for the system and reserve area
The findings help determine whether a conventional septic system may be suitable or whether the property requires an alternative or engineered design. They also help identify where the system can be installed without conflicting with buildings, wells, property lines, washes, easements, and other site features.
Learn more about Ponderosa Environmental’s soil site investigation services.
Can Every Arizona Property Support a Conventional Septic System?
No. Some properties can support a conventional septic system, while others require an alternative or engineered design. In some cases, site constraints may make the proposed development impractical without significant changes.
A conventional system may not be suitable when a property has:
Unsuitable or shallow soils
Bedrock near the surface
Steep slopes
High groundwater
Limited usable area
Conflicts with required setbacks
Floodplain or wash hazards
High expected wastewater flows
Nonresidential or high-strength wastewater
These factors don’t always mean the property can’t be developed. An alternative system, a different building location, a smaller project, or changes to the site plan may provide a workable solution.
The appropriate system can only be determined after reviewing the soil, site conditions, proposed use, and expected wastewater flow. A neighboring property’s approval doesn’t guarantee that the same type of system will work on your parcel.
Conventional vs. Alternative Septic Systems
Septic systems generally fall into two categories: conventional and alternative. The right option depends on the property, the proposed use, and the applicable regulations.
Conventional Septic Systems
A conventional septic system typically uses a septic tank and a gravity-based disposal area. Wastewater flows into the tank, where solids separate from the liquid. The effluent then moves by gravity into the disposal area, where the soil provides additional treatment.
Conventional systems may be appropriate when the soil, slope, available space, setbacks, and other site conditions meet the applicable requirements.
Alternative Septic Systems
An alternative septic system provides additional treatment or uses a different method to distribute wastewater when a conventional system isn’t appropriate. Depending on the site and reviewing agency, possible technologies may include:
Pressure distribution
Aerobic treatment
Textile or media filtration
Mound systems
Drip dispersal
Other engineered treatment technologies
Not every option is permitted or appropriate for every property. Some alternative systems also require electrical components, ongoing maintenance, monitoring, or service agreements.
The system should be selected based on the site evaluation, wastewater characteristics, design flow, and applicable regulations. It shouldn’t be chosen from a list based only on price or preference.
What Is the Arizona Septic Permitting Process?
The exact septic permitting process varies by county, system type, and project. However, most Arizona projects follow these general steps:
Confirm the permitting authority.
Determine whether the application will be reviewed by the county or directly by ADEQ.Complete a soil and site investigation.
Evaluate the soil, slope, available area, setbacks, and other conditions that may affect the system.Determine the appropriate system type.
Use the investigation findings and proposed wastewater flow to determine whether the property needs a conventional or alternative system.Prepare the design and supporting documents.
Develop the septic design, site plan, calculations, reports, and other materials required by the reviewing agency.Submit the application.
Submit the permit application, Notice of Intent to Discharge, design, and supporting documents.Complete agency review.
The reviewing agency checks the application for compliance. The designer may need to answer questions, revise documents, or submit additional information.Receive Construction Authorization.
Construction Authorization allows the approved system to be installed. Installation shouldn’t begin before this authorization is issued.Install the approved system.
A qualified contractor installs the system according to the approved design and permit conditions.Complete inspections and documentation.
The system must pass the required inspections. Final plans, installation records, certifications, or other documents may also be required.Receive Discharge Authorization.
Discharge Authorization must be issued before wastewater is discharged into the system.
County forms, fees, review procedures, and inspection requirements aren’t identical across Arizona. Confirm the current process with the applicable permitting authority before beginning the investigation, design, or installation.
What Determines the Size of a Septic System?
Septic system size isn’t based only on how many people currently live or work at the property. It’s based on the amount and type of wastewater the proposed building is expected to generate.
For residential projects, the number of bedrooms is often used to establish the design flow. This accounts for the home’s potential occupancy rather than the number of current residents. Plumbing fixtures and facilities, such as large bathtubs or multiple laundry areas, may also affect the design.
Commercial and other nonresidential properties are evaluated differently. The expected flow may depend on the building’s use, operating capacity, plumbing fixtures, and the number of employees, customers, students, seats, or other users. Wastewater strength also matters. Restaurants, food-production facilities, and some commercial operations can produce wastewater that requires additional treatment.
The final system design may be influenced by:
Number of bedrooms
Building use and expected occupancy
Expected design flow
Plumbing fixtures and facilities
Residential or commercial use
Wastewater strength
Soil and site conditions
Disposal or treatment technology
Applicable agency requirements
These factors affect the capacity of the septic tank, treatment components, and disposal area. Soil conditions are especially important because they influence how much disposal area is needed to treat and disperse the wastewater safely.
Future plans should be considered during the original design. Adding bedrooms, converting a building to a different use, or expanding a commercial operation may increase the approved design flow. The existing system may need to be evaluated, altered, or replaced before the change can be permitted.
How Much Space Does a Septic System Need?
There’s no universal square-foot requirement for a septic system. The amount of land needed depends on the expected wastewater flow, soil and site conditions, system type, required setbacks, and the layout of the property.
The site may need enough usable space for:
The septic tank and any treatment components
The primary disposal area
A reserve disposal area
Required setbacks
Installation and maintenance access
Separation from buildings, wells, property lines, washes, easements, and other site features
The reserve area is especially important. It must remain available for a replacement disposal area if the original one can no longer be used. A driveway, building, pool, or other permanent improvement generally shouldn’t be placed where it would interfere with the approved primary or reserve area.
This is why total lot size can be misleading. A large parcel may still have limited usable space because of steep slopes, shallow soil, bedrock, washes, easements, or setback conflicts. Septic planning should be coordinated with the overall site plan before the locations of the home, driveway, well, and other improvements are finalized.
How Much Does a Septic System Cost in Arizona?
There isn’t one reliable statewide price for a septic system in Arizona. Costs vary considerably from one property to another based on the site conditions, system requirements, and permitting authority.
The total project cost may include:
Soil and site investigation
Surveying or site mapping
Septic system design
Permit and review fees
Tank and system materials
Excavation and site preparation
Installation
Electrical or mechanical components
Required inspections and final documentation
Ongoing maintenance
The type of system is one of the biggest cost factors. A straightforward conventional system will generally cost less than an engineered alternative system. Alternative systems may require specialized treatment components, pumps, controls, electrical service, monitoring, or regular professional maintenance.
Installation conditions also matter. Rocky soil, shallow bedrock, steep terrain, limited equipment access, or a difficult tank location can increase excavation and labor costs. Permit fees and review requirements may also differ by county and system type.
The property’s conditions should determine the design. Choosing land based on an assumed septic budget before evaluating the site can create expensive surprises. A soil and site investigation provides a much better starting point for understanding what the property may require.
How Long Does Septic Approval Take?
There’s no standard approval timeline for every septic project in Arizona. The process may take longer or shorter depending on the property, proposed system, and reviewing agency.
Timing can be affected by:
The county’s current workload
Whether the application is complete
Site and soil complexity
Conventional versus engineered system design
Agency questions or review comments
Required revisions and resubmittals
Related zoning, floodplain, building, or development approvals
Contractor scheduling
Inspection availability
A complete application for a straightforward conventional system may move more quickly than an engineered design for a complex site. Missing documents, conflicting site plans, or unresolved property constraints can add time to the review.
Begin the septic evaluation before finalizing the building location or construction schedule. Early planning gives the designer time to identify site constraints and coordinate the septic system with the home, driveway, well, utilities, and other improvements.
Common Septic Mistakes to Avoid Before Building
Many septic problems begin before installation. Decisions about the land, building location, and site layout can limit the available system options or lead to costly revisions later.
Common mistakes include:
Buying land without evaluating septic feasibility. A parcel may not have suitable soil or enough usable space for the proposed development.
Finalizing the building location first. The home, driveway, well, utilities, and septic system need to be planned together.
Assuming a neighboring property proves your parcel will work. Soil, slope, setbacks, and other conditions can change considerably between nearby properties.
Treating the septic tank as the entire system. The disposal area, reserve area, and underlying soil are also essential parts of wastewater treatment.
Forgetting the reserve area. This space must remain available for a future replacement disposal area and shouldn’t be developed or disturbed.
Ignoring future plans. Additional bedrooms, guest houses, workshops, or changes in use may increase wastewater flow and require a larger or different system.
Building over or disturbing the septic area. Buildings, pools, driveways, grading, and heavy equipment can damage system components or make approved areas unusable.
Installing the system before receiving authorization. Construction shouldn’t begin until the applicable agency has issued Construction Authorization.
Choosing a system based only on its initial price. Installation, maintenance, electrical use, service requirements, and expected system life should also be considered.
Assuming every Arizona county follows the same process. Forms, fees, submission procedures, review requirements, and inspections can differ by county.
The best time to identify septic constraints is before buying the property or finalizing the site plan. Early evaluation leaves more options for adjusting the project before those changes become expensive.
How to Protect Your Septic System After Construction
Once your septic system is installed, regular care can help prevent damage, backups, and premature system failure.
Pump the tank based on the system’s actual needs. Pumping frequency depends on tank size, wastewater use, occupancy, and the amount of solids that collect. Have the tank evaluated by a qualified professional instead of relying on a universal schedule.
Keep maintenance records. Save permits, approved plans, inspection reports, pumping receipts, service records, and information about repairs or replacement parts.
Don’t drive or build over the system. Vehicles, heavy equipment, buildings, pools, patios, and other improvements can damage components or compact the soil.
Protect the disposal and reserve areas. Avoid grading, excavating, paving, or planting deep-rooted trees where they could interfere with the system.
Be careful about what goes down the drain. Don’t flush wipes, grease, chemicals, medications, hygiene products, or other materials that can clog the system or disrupt treatment.
Conserve water and repair leaks. Excess water can overload the system. Fix leaking fixtures and spread high-water-use activities throughout the week when possible.
Follow the manufacturer’s requirements. Alternative systems may require regular servicing, inspections, replacement parts, monitoring, or an active maintenance agreement.
Complete required inspections. Follow all operation and maintenance requirements established by the permit, manufacturer, and applicable regulatory agency.
Contact a qualified professional if you notice slow drains, sewage odors, unusually wet soil, standing water near the disposal area, alarms, or wastewater backing up inside the building. Addressing warning signs early may prevent more serious damage.
What Happens When You Sell a Property With Septic?
When ownership of an Arizona property with a septic system transfers, the system generally must be inspected by a qualified inspector. This requirement applies to both conventional septic systems and alternative onsite wastewater systems.
The transfer process typically works as follows:
The seller arranges for the inspection within six months before the property transfer.
The inspector completes a Report of Inspection and provides it to the seller.
Before closing, the seller gives the report and any available permitting, operation, and maintenance records to the buyer.
The buyer submits a Notice of Transfer and the applicable fee to the proper agency within 15 calendar days after the transfer.
An inspection exemption may apply if the system has never been used, but the buyer must still file the Notice of Transfer. Sellers and buyers should confirm the current requirements and filing agency for the property before closing.
Visit ADEQ’s Notice of Transfer and Inspection page for current forms and instructions.
How Ponderosa Environmental Can Help
Ponderosa Environmental helps property owners, builders, and developers understand what a site can support before construction begins. Our experienced team provides:
Property and project reviews
Soil site investigations
Conventional septic system design
Alternative and engineered septic system design
Residential and commercial project support
Community and subdivision wastewater planning
Permit-ready reports and supporting documentation
Coordination through agency review comments and revisions
We evaluate the property, identify potential constraints, and prepare the documents required by the applicable reviewing agency. Starting this work early can help keep the septic design, site plan, and proposed development aligned.
Planning a project in Arizona? Evaluate the property before you build.
Key Takeaways
Begin septic planning before finalizing the building location and site plan.
Arizona regulates septic systems to protect public health and groundwater.
Most septic applications are submitted through the county where the property is located.
Soil and site conditions determine whether the property can support a conventional system or requires an alternative design.
The site must have enough usable space for the system, required setbacks, and reserve disposal area.
Construction Authorization is required before installation, and Discharge Authorization is required before the system can be used.
Evaluating the property early can help prevent redesigns, project delays, and unexpected costs.
Frequently Asked Questions
-
A septic system is an onsite wastewater treatment system.
It collects wastewater from a building, separates solids in a septic tank, and sends the remaining effluent to a disposal area where the soil provides additional treatment. -
Most new septic projects require a soil and site investigation before the system can be designed and approved.
The investigation evaluates the soil, slope, available space, setbacks, and other conditions that affect the system. -
No. Properties with unsuitable soil, shallow bedrock, steep slopes, limited usable space, high groundwater, or setback conflicts may require an alternative or engineered system.
Some sites may require changes to the proposed development. -
There’s no single minimum lot size that works for every property.
The site must have enough suitable space for the tank, treatment components, primary disposal area, reserve area, required setbacks, and maintenance access. -
Approval times depend on the county, system type, site conditions, application completeness, and any required revisions.
Engineered systems and complex properties may take longer to review than straightforward conventional systems. -
Don’t assume construction can begin before septic approval.
Septic feasibility can affect the building location and overall site plan, and the applicable building or development permits may depend on receiving septic approval.
Confirm the required order of approvals with the county before starting construction. -
ADEQ establishes Arizona’s statewide onsite wastewater requirements.
Most septic applications and permits are handled by the county where the property is located through delegated authority, although some projects may require direct ADEQ involvement.