Can You Have Two Septic Systems on One Property

By Stephen methew

Can You Have Two Septic Systems on One Property? Having two septic systems on one property is a possibility under certain circumstances. While most properties only require a single septic system, there are situations where installing a second system becomes necessary or advantageous.

In this comprehensive guide, we will explore when and how dual septic systems can be utilized, the requirements and considerations involved, and the pros and cons of this approach. Whether you are a homeowner with multiple structures on your property or a potential buyer weighing your options, understanding the intricacies of dual septic systems will help you make informed decisions.

Can You Have Two Septic Systems on One Property

When Are Two Septic Systems Needed?

The primary reason for considering two septic systems on one property is when there are two separate structures requiring wastewater treatment. This commonly applies to properties with a main house and an additional dwelling, such as a guest house, pool house, or detached garage with plumbing and bathroom facilities.

Other scenarios include farms with a main farmhouse and a secondary barn or outbuilding needing wastewater management, home businesses with an office building or warehouse with restrooms, and multi-family properties with multiple separate residential structures. In these situations, installing two distinct septic systems, one for each building, is often mandated by local plumbing and septic codes, as a single septic system may not be sufficient to support multiple occupied dwellings.

Septic System Requirements and Capacity

When installing any septic system, it is crucial to ensure that it is appropriately sized and designed to handle the generated wastewater volumes adequately. Several factors influence the type and size of the system required:

  1. Number of bedrooms and bathrooms: The more bedrooms and bathrooms a structure has, the higher the wastewater volume it will produce.
  2. Daily water usage: The amount of water used by the occupants affects the total wastewater output.
  3. Soil conditions: The type of soil on the property plays a role in the drainage capacity and treatment efficiency of the septic system.
  4. Lot size and layout: The available space on the property determines whether there is enough room for two full drain fields and tanks.

To ensure both systems work effectively, each must be adequately sized and located based on the projected daily wastewater volumes of the specific structure it serves. Attempting to connect two dwellings to an undersized single system or forcing one structure to rely on the other could lead to premature system failure.

Is Dual System Installation Allowed?

The permitting requirements for septic systems are typically managed at the county or local level. Most areas require separate permits and inspections for each septic tank and drain field installed on a property. Before proceeding with a dual septic installation, it is essential to check with the local health department or permitting office to understand the specific rules and obtain approval.

Generally, getting permits approved for two septic systems is straightforward, provided there is adequate space on the lot for two code-compliant systems, and they are situated at proper distances from structures, wells, and property lines.

How Much Does a Dual Septic System Cost?

Installing two septic systems instead of one will increase the total project budget. The exact cost increase depends on several factors, including:

  1. Type of systems being installed: Different types of septic systems, such as standard gravity-fed drain fields or advanced treatment systems, come with varying price tags.
  2. Size and capacity: Larger tanks and drain fields are required for systems designed to handle more wastewater.
  3. Layout: If the property has challenging terrain, drainage issues, or limited space, additional expenses may be incurred during installation.
  4. Degree of site work: Complex topography or the need for retaining walls and fill to create a usable area can drive up costs.
  5. Local labor and material rates: Costs are typically higher in areas with high real estate values and demand.

As a rough estimate, expect to pay anywhere from 50% to 100% more for a dual septic installation compared to a single system. It is also essential to consider the ongoing maintenance costs, which will be multiplied with two systems.

Pros and Cons of Two Septic Systems

Like any decision, opting for two septic systems on one property comes with its own set of advantages and disadvantages. Let’s take a closer look at these:


  1. Fully Separate Wastewater Treatment: Each structure has its independent wastewater treatment, ensuring compliance with codes and regulations.
  2. Prevents Overloading: By having two systems, the risk of overloading a single undersized system is eliminated, reducing the likelihood of system failure.
  3. Independent Functionality: Dual septic systems allow both structures to operate independently, providing flexibility for the occupants.
  4. Spreads Environmental Impact: The environmental impact of wastewater treatment is distributed over two drain fields, potentially minimizing its effects on the property.


  1. Higher Upfront Installation Costs: Installing two systems incurs higher initial costs compared to a single system.
  2. Increased Maintenance Costs: Owning and maintaining two systems can be more expensive over time.
  3. Need for Adequate Space: Two drain fields require sufficient healthy soil and space on the property.
  4. Complex Installation: Dual septic installation demands extensive planning and coordination.

How to Determine if You Need Two Systems

If you are considering adding a second occupied structure to your property, the first step is to consult your local health department to understand the system requirements. An on-site inspection and soil analysis will help determine whether your lot can feasibly support two septic systems.

The inspector will evaluate key factors such as:

  1. Lot Size: Small lots may not have enough room for two drain fields.
  2. Soil Suitability: Perc tests will be conducted to determine if the soils can adequately absorb wastewater.
  3. Topography: Steep slopes or irregular shapes may limit installation options.
  4. Setbacks: Adequate distances must separate the systems from buildings and property lines.

Based on the property conditions and projected sewage volumes, the inspector can then advise you on the most practical wastewater treatment approach.

Frequently Asked Questions about Can You Have Two Septic Systems on One Property

Can I have two septic tanks with one drain field?

No, separate drainage systems are required for each septic tank. A single drain field would become overloaded and lead to system failure.

What distance should two septic systems be separated?

There should be at least 10 feet of separation between the closest edges of the two drain field areas. More separation distance is even better for efficient wastewater treatment.

Can I just pump one septic tank to the other’s drain field?

No, each drain field is specifically designed and sized for the projected sewage volume from the structure it serves. Sending excess waste to the wrong drain field will cause the system to fail.

What about using a septic holding tank instead of a drain field?

While permitted in some areas, holding tanks are designed for temporary wastewater storage and are not suitable for long-term treatment of actively used structures.

Can I have two homes share an advanced treatment system?

Potentially, if the advanced treatment system is adequately sized and approved by the local health department. However, two standard gravity flow drain fields would still be required to ensure proper wastewater treatment.

How close can two septic tanks be?

The distance between two septic tanks can vary depending on local regulations, soil conditions, and the specific requirements of the septic system design. Generally, septic tanks should be placed at a sufficient distance to ensure proper functioning and avoid interference between the tanks.

What will be septic tank size for 2 houses?

The size of a septic tank for two houses will depend on several factors, including the number of bedrooms in each house, local regulations, soil conditions, and the expected daily wastewater flow. Generally, when serving multiple households with a single septic tank, the tank’s size and design must accommodate the combined wastewater flow from both houses.

Why do I have 2 septic tanks?

Having two septic tanks can be due to several reasons, and each situation is unique based on factors such as property size, multiple dwellings, backup or redundancy, local regulations, household needs, separation of waste, environmental protection, future expansion , and soil conditions.

How many septic tanks can be built per acre?

The number of septic tanks per acre can vary widely depending on factors such as local regulations, soil conditions, water table levels, property size, and the intended use of the land. Generally, the number of septic tanks per acre is determined by considering aspects like soil percolation rate, regulations, wastewater generation, topography and advanced treatment systems.

Can I have Multiple septic tanks?

A house/property can have multiple septic tank. There are several reasons why a property might have multiple septic tanks including Increased Wastewater Load, Separation of Graywater and Blackwater, Guest Houses or Outbuildings, Zoning and Regulations, Limited Space or Soil Conditions, Backup System, Seasonal Use.


Having two septic systems on one property is a viable solution in situations where multiple structures require independent wastewater management. Thorough research, consultation with local authorities, and expertise from experienced septic contractors are essential for the successful installation and long-term functionality of dual septic systems.

While the upfront costs and maintenance may be higher compared to a single system, the benefits of fully separate wastewater treatment and reduced risk of overloading can outweigh the drawbacks for certain property owners. If you are considering dual septic systems, it is crucial to make informed decisions and prioritize both the well-being of the environment and the long-term functionality of your property’s wastewater treatment.


  1. United States Environmental Protection Agency (EPA) – Septic Systems:
  2. National Environmental Services Center (NESC) – Homeowner’s Guide to Septic Systems:
  3. University of Minnesota Extension – Septic Systems:
  4. Ontario Ministry of Agriculture, Food and Rural Affairs – Septic System Maintenance:
  5. Penn State Extension – Septic Systems: What You Need to Know:

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