Do ADU’s Need a Separate Septic System?

Accessory Dwelling Units (ADU), commonly called granny flats or in-law apartments, are a great alternative for affordable housing, especially in areas with an inflated real estate market (and limited housing supply). These units serve as a secondary residence on the same property as the primary dwelling, which can be used for elderly relatives, adult children, and low-income families. Since the State of California revised its zoning regulations to simplify and enable ADU construction, it has become a popular solution for residents and raised several inquiries about the construction process. For instance, what about the sewage system and other considerations for building an ADU?

We are going to break down the details that you need to know about septic systems for ADU’s before you decide to construct a secondary unit on your property.

Septic Systems And ADU’s

Properties that are not connected to a public sewer system require an Onsite Wastewater Treatment System(OWTS), otherwise known as a septic system. Because septic systems are typically based on total household size, ADU’s will need a separate system as the primary dwelling’s system would not have the capacity to support additional occupants residing in the ADU. Before homeowners can begin designing an ADU to build on their property, there are some preliminary tasks to carry out prior to applying for any building permits to ensure that your site can meet the standard building guidelines and local plumbing code.

First and foremost, you will need to set up a site evaluation to determine whether or not a septic system is feasible for the ADU development site. The septic experts at Acuantia can guide you through this process which entails:

  • Soil evaluation for home septic systems
  • Measuring soil depth
  • Percolation test (soil absorption rate)
  • Review of limiting conditions (impermeable soil, high groundwater, etc.)
  • Verifying availability of disposal area for system installation or replacement
  • Maintaining setback clearance requirements
  • Reviewing physical site features of the lot and area next to the disposal system

Following a successful evaluation, homeowners can select the appropriate septic system to install for the ADU site design. Depending on the development site and space availability, the septic contractor will present your options which may include a leach field or seepage pit septic system.

Make sure that you check with the applicable local state department authorities – such as, Environmental, Housing, and Public Health – about all policy regulations for standard building guidelines (for example, maximum building square footage, height, setback distances, and fire safety stipulations) and the necessary permit documents that you’ll need to begin the ADU construction and installation of your septic system. It’s important to remember that the entire process of applying for and receiving approval permits takes time, so you’ll need to account for this in your budget and project timeline.

Why Choose Acuantia?

We solve homeowners’ onsite wastewater needs by:

  • Providing a one-stop-shop experience
  • Partnering with trusted, high-quality service providers
  • Affordably managing your project end-to-end
  • Simplifying the complicated onsite wastewater experience
  • Managing and completing your job to the highest standard
  • Maintaining your septic system to keep it running into the future

Here at Acuantia, we pride ourselves in being your one-stop shop solution for all of your septic needs, from site evaluation and design through installation and routine maintenance. Our professional team coordinates with you and all kinds of developers to save you time and money on your septic system. For additional information about our services, contact us today!

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