When dreaming up your ideal ADU, you likely had a design in mind, along with the aesthetics, amenities, furniture, and even tenants. What you may have omitted, however, are the not-so-appealing questions like how you’ll handle wastewater treatment and sewage.

Unless your home is connected to a municipal sewer system, installing or upgrading a septic system is likely needed to support your ADU. Fortunately, this guide will walk you through everything you need to know about septic systems and ADUs— so you don’t get backed up in the process.

Assessing Your Existing Septic System

Before any design sketch turns into a concrete structure, ADU pros, like us, will ask you one fundamental question: Do you have an existing septic map?

If that draws a blank or you’re frantically searching through old property files, it might be time to consult a septic specialist. This map will provide a clear layout of the tank size, leach lines, and reserve field. Sometimes, this golden ticket of information is tucked away in county portals. If not, the adventure of using a septic locator awaits you. Now, if this is already making your head spin a tad, fear not! Here’s a pro tip: A seasoned septic professional can be your compass, determining whether your existing system can cater to the additional wastewater demands of your ADU.

Every time a client mentions they’re on septic, our antennas go up. We’ll need to know where this tank is located, because we cannot build on top of an existing septic tank, leech line, or reserve field. If this proves not to be an issue, we’ll swiftly navigate the conversation to tank sizes and room numbers. The logic is simple: more rooms generally mean more wastewater. If your septic tank can’t handle that, it’s time for a chat on upgrading or expanding your septic setup. And this isn’t just about avoiding messy situations; it’s also about ensuring your ADU remains compliant with local health regulations.

Not sure where to begin? Our ADU experts at ADU Geeks are available to provide the answers you’re looking for.

 

ADU Waste Management in California

In California, you can expect strict regulations around septic system installations and upgrades. To avoid any unforeseen issues and keep your project moving, we recommend you contact your local health department and obtain all necessary construction permits early in the ADU planning process. 

In the meantime, here are some key statewide septic system requirements to consider:

• Minimum tank sizes based on number of bedrooms
• Legal distances from buildings, wells, property lines, natural water bodies and slopes
• Regular maintenance like septage pumping every 3-5 years
• Restrictions on non-organic items discharged into the system

Here’s a simple table to understand what your minimum tank size will be, depending on how many bedrooms you have in your ADU:

(via San Diego County)

Following all rules and regulations ensures your septic system functions safely and sustainably for the long-term. On the contrary, not complying can lead to environmental and health hazards for your family and your community—and that would downright stink. 

 

What Does a Septic System for an ADU Cost?

While costs can vary depending on location and unique circumstances, installing a septic system for your ADU can cost an additional anywhere from $30k to $70k, if not more. 

Depending on your property and whether or not it can accommodate a septic system, you may need to add a sewage pump which can cost an an estimated $5k or more.

Because so many factors go into the costs associated with a septic system, it is highly recommended to consult with an ADU professional who could assess your property and unique situation and provide a much more accurate estimate.

 

ADU Waste Management in San Diego

While many of the regulations around ADU septic systems in California are the same, there are certain regulations that differ depending on location. 

In San Diego County, septic system permits are issued by the Department of Environmental Health. That’s who you’ll want to connect with at the start of the ADU planning process.

While we love our spectacular beaches, sandy soils mean that septic drainfields may need to be larger than in other regions. 

With San Diego’s mild winters, septic systems don’t get the cold weather “down time”, so proper maintenance and pumping every 3 years is recommended.

San Diego County has specific septic system setback requirements from environmentally sensitive areas, slopes, intermittent waterways, and property lines that must be followed.

Planning for septic systems may not be the most glamorous part of an ADU project, but it’s a critical one. A properly designed and maintained septic setup ensures your ADU’s waste flows smoothly without nasty backups or environmental hazards.

While septic considerations can seem complex, the ADU experts at ADU Geeks are here to help. Our team of knowledgeable ADU pros are happy to discuss septic tanks, leach fields, regulations, costs and creative alternatives, and even put you in touch with other experts in the industry. We’ll assess your property’s unique needs and guide you through the septic planning process, ensuring your ADU has a safe, sustainable wastewater solution. Schedule a consultation today!

 

ADU Geeks is ready and willing to take your ADU project from conception to completion.

Put us on your team and we’ll walk you through the entire process, including site prep, design, permitting, and construction.

Best of all, you have a front-row seat to watch your new ADU come to life.

Book a consultation call with us today. It’s free, it takes only 15 minutes of your day, and, when we’re done, we’ll be able to figure out what ADU option works best for you, your family, and your property.

Do you have questions?

We love questions.

Make sure you bring them up during your 15-minute call so we can address all of your concerns. We’re looking forward to hearing from you and setting you up for the retirement home you deserve.

This material has been prepared for informational purposes only, and is not intended to provide, and should not be relied on for, tax, legal, or accounting advice. You should consult your own tax, legal, and accounting advisors before engaging in any transaction.