Do I Need Septic to Build on Vacant Land in the High Desert?

If you're looking at vacant land in Joshua Tree, Twentynine Palms, Yucca Valley or another part of the California High Desert, you may be thinking about water, electricity, road access and building costs.

But there is another important question:

Where is everything going to go after you flush the toilet?

It's not the most glamorous part of buying desert land, but wastewater disposal can be an important part of determining whether a parcel works for the home you want to build.

In many parts of the High Desert, public sewer service isn't available. If sewer is not available to the property, residential construction will generally require an approved onsite wastewater treatment system (OWTS), commonly called a septic system.

Before buying land you plan to develop, it's important to understand that owning several acres does not automatically mean you can simply put a septic system wherever you want.

Do You Need a Septic System to Build a House in the High Desert?

If public sewer is available and the property can connect to it, sewer may be the required wastewater solution.

When sewer service isn't available, San Bernardino County requires a home builder to construct an approved onsite wastewater treatment system.

This is common with vacant land throughout the desert.

That's why a parcel advertised as:

“5 acres ready to build!”

still leaves quite a few unanswered questions.

One of them is wastewater.

What Is a Septic System?

A septic system is a privately owned wastewater treatment and disposal system.

Instead of wastewater leaving the property through a municipal sewer line, it is treated and dispersed onsite. San Bernardino County describes these systems as having two basic components: a septic tank and a disposal field.

For a land buyer, the important takeaway is simple:

The property itself has to accommodate the wastewater system required for the proposed development.

That means septic should be part of your land research—not something you first think about after you've purchased the property.

What Is a Perc Test?

This is one of those terms vacant-land buyers hear constantly:

“Has the property been perc tested?”

A percolation—or perc—test helps determine how water is absorbed by the soil and provides information used in designing an appropriate onsite wastewater system.

San Bernardino County Environmental Health Services requires qualified professionals to conduct percolation testing and reviews submitted reports to evaluate the testing, calculations and proposed design rate.

A perc evaluation isn't simply somebody digging a hole, pouring water into it and saying:

“Yep. Looks good.”

The County's standards consider parcel-specific soil conditions along with topographical, geological and hydrological factors.

In other words:

Your shoe is not a geotechnical instrument.

Even if the dirt looks perfectly normal while you're standing on it.

Does Every Vacant Lot Need a Perc Test Before I Buy It?

Not necessarily before you purchase it—but if you intend to build and the property will require an onsite wastewater system, wastewater feasibility belongs on your due-diligence list.

There may also be historical information available for some parcels. San Bernardino County Environmental Health Services maintains archival information that may help establish percolation rates previously assigned to properties.

Whether existing information can be used for your particular project is something to verify with the County and the appropriate professionals.

The important thing is not to assume.

Ask questions such as:

• Is public sewer available to this parcel?
• Has the property previously been perc tested?
• Is there an existing approved perc report?
• Will new testing be required for my proposed project?
• What type of onsite wastewater system may be appropriate?
• Are there site conditions that could affect placement or design?

Those answers can matter before you decide what a parcel is worth to you.

Why Doesn't Having Five Acres Automatically Solve the Septic Question?

This is a common High Desert misconception.

A buyer sees five acres of open desert and thinks:

“There's plenty of room for everything.”

Maybe.

But acreage alone doesn't determine septic feasibility.

The County evaluates site-specific conditions, including soil characteristics, geology, groundwater considerations and the proposed wastewater dispersal system. The LAMP also establishes setback and siting requirements that can affect system design.

Your future house isn't the only thing competing for space on the property, either.

Depending upon the project, you may eventually be planning locations for:

• The home
• Septic tank and disposal area
• Water lines
• A private well, if applicable
• Driveway and access
• Garage or workshop
• ADU or other future improvements
• Utility infrastructure
• Required setbacks

Suddenly five acres isn't just five acres of empty dirt.

It's a site plan.

Can I Just Install the Septic System Wherever I Want?

No.

The septic system has to be appropriately designed and permitted.

San Bernardino County requires a building permit before installation of a new or replacement onsite wastewater treatment system. The County also identifies qualifications for professionals involved in OWTS design and installation.

Environmental Health Services reviews septic-related information, including percolation reports, while Building and Safety handles the construction permitting process. Depending on the property and system, additional review can sometimes be required.

This is another reason I tell buyers:

Don't design the dream house before you understand the dirt.

The characteristics of the parcel can influence what makes sense to build and where.

Does the Size of the House Affect the Septic System?

It can.

For residential systems, San Bernardino County explains that septic sizing considers the number of bedrooms rather than simply counting bathrooms.

That's worth remembering if you're buying land with plans for future expansion.

Perhaps you're thinking:

"I'll build something small now and make it bigger later."

Great.

But future plans are worth discussing during the original feasibility and design process rather than assuming the wastewater system you install today will automatically accommodate whatever you decide to build ten years from now.

What If There's an Old Cabin—or Evidence One Used to Be There?

Be careful with this one in the High Desert.

There are parcels throughout the Morongo Basin with old cabins, cabin remnants, concrete pads or evidence that a structure once existed.

That does not automatically tell you that an approved septic system exists.

Many of the old desert recreational cabins were extremely basic structures. The fact that someone built or used something on the land decades ago does not establish that today's residential development requirements have been satisfied.

If a listing says:

“Old cabin site”

or

“Existing building pad,”

consider that interesting property history—not proof that the parcel is ready for a modern residence.

Verify what actually exists.

What If a Land Listing Says “Septic Area”?

You'll occasionally see vacant land described with phrases such as:

• Septic area
• Septic required
• Buyer to install septic
• No sewer
• Perc test completed
• Septic approved

These statements don't all mean the same thing.

“Septic area” does not mean there is already a septic system.

“Septic required” does not mean the property has already been approved for your proposed system.

And even if a previous perc test or septic approval exists, determine whether it is applicable to what you intend to build.

This is why I encourage buyers to look beyond the marketing remarks.

The listing description is where your investigation begins—not where it ends.

How Much Does a Septic System Cost in the High Desert?

There isn't one reliable number I would tell every buyer to use.

Costs can depend on the site, system design, soil conditions, excavation, engineering or professional services, permits, system size and the type of wastewater solution required.

That's why I prefer to tell buyers to:

Price the project, not just the dirt.

A $15,000 parcel that requires substantially more site work may ultimately be more expensive to develop than a $30,000 parcel with characteristics that better fit the project.

Purchase price is only one part of the land-buying equation.

Should I Investigate Septic Before Making an Offer?

If your intended use requires a residence, wastewater should absolutely be part of the questions you investigate.

How far you go before making an offer versus during an appropriate due-diligence period will depend on the property and transaction.

At minimum, you should understand whether sewer is available and whether septic is likely to be required.

For a property you're seriously considering, you may want additional investigation by San Bernardino County and qualified septic, engineering, geology or environmental-health professionals as appropriate.

Water + Power + Access + Septic

When buyers call me about High Desert land, they're often initially focused on acreage and price.

Those are important.

But if you're planning to build, I want you thinking about the bigger picture:

Can I legally access it?

Where will my water come from?

How will I get power—or will I build off-grid?

How will wastewater be handled?

Can the property accommodate what I actually want to build?

That's how you begin evaluating land as a future homesite rather than simply evaluating dirt by the acre.

Buying Land in Joshua Tree, Twentynine Palms or Yucca Valley?

You don't have to find the property through Sell29 for me to help you buy it.

You may find a parcel on Zillow, Realtor.com, Land.com, through another real estate agent's listing, or while driving around the desert.

If you find land you're interested in, send me the APN or listing.

Tell me what you're hoping to do with the property, and I can help you identify some of the questions you'll want to investigate before deciding whether that parcel makes sense for your plans.

A national real estate website can show you what's listed.

I can help you understand the landscape.

Looking for High Desert Land?

Tell me what you're looking for—including your budget, preferred acreage, intended use and whether water, power or easy road access are important to you.

Dawn Anderson is a California real estate broker serving buyers and sellers in the High Desert. Information provided here is general educational information and is not engineering, geological, septic, legal or permitting advice. Requirements vary by parcel and proposed use. Buyers should verify wastewater feasibility, permits, zoning, utilities and development requirements directly with San Bernardino County and appropriate qualified professionals before purchasing or developing property.