Percolation testing & septic system design
Building on a lot without a sewer connection? A perc test shows whether the ground can absorb wastewater — and the design that follows gets your septic system approved.
What it is
Much of the Antelope Valley — large parts of Littlerock, Lake Los Angeles, Quartz Hill, and the outskirts of Lancaster and Palmdale — has no public sewer. Homes there rely on an onsite wastewater treatment system (OWTS): a septic tank plus a leach field or seepage pit that lets treated water soak back into the ground.
A percolation test ("perc test") measures how fast water soaks into the soil on your lot. We dig test holes or drill a deep boring where the system will go, pre-soak the soil, then measure how quickly the water level drops. That rate tells the county whether a septic system will work there, and how large the leach field or seepage pit must be.
From those results we prepare a stamped percolation report and, if you need it, the septic system design — tank size, disposal-field or seepage-pit sizing, and a layout drawing — for submittal to the Los Angeles County Department of Public Health, Environmental Health. For lots in Rosamond and the rest of eastern Kern County, the reviewing agency is Kern County Environmental Health.
Why perc rates vary so much here
Antelope Valley soils range from fast-draining sand and gravel to tight clays and cemented caliche layers that water barely moves through. Two lots on the same street can test very differently, which is why the county requires testing on your specific parcel.
When you need it
You'll need perc testing — and usually a septic design — in any of these situations.
New home on a lot without sewer
The county won't approve the building permit until the septic system design, based on a perc test, is approved.
Adding bedrooms or an ADU
More bedrooms means more wastewater. An existing system often has to be evaluated and expanded, with new testing.
Replacing a failed system
A failing leach field or seepage pit usually needs new testing in a fresh location before a replacement can be designed.
Buying vacant land
Testing before you close tells you whether the lot can support a septic system at all — and roughly what it will cost.
Lot split or subdivision
Each new parcel without sewer must show it can support its own system.
Agency or lender request
If Environmental Health, a lender, or an escrow officer asked for a perc test, send us their request and we'll match the scope to it.
What's included
- Review of the parcel, proposed building layout, and county requirements for the system type
- Utility clearance through DigAlert (811)
- Test holes or a deep boring at the proposed system location
- Pre-soak and timed percolation measurements per the reviewing agency's procedures
- Soil logs and groundwater observations
- Stamped percolation test report
- Septic system design: tank sizing, leach field or seepage pit sizing, and layout plan (when included in scope)
- Submittal support and responses to Environmental Health review comments
Typical timeline
- Day 1
Quote & scope
Send the APN, the planned house size and bedroom count, and any county correspondence.
- Scheduling
Site visit booked
Utilities cleared and testing scheduled. Typical lead time: [NEEDS FROM MOHAMMED: typical perc-test scheduling lead time].
- 1–2 days on site
Testing
Holes are dug or drilled, pre-soaked, and measured — some procedures require an overnight soak.
- Final
Report & design
Stamped perc report (and septic design, if included). Titan's typical turnaround: [NEEDS FROM MOHAMMED: typical perc report / septic design turnaround].
County review time is set by the agency and is not included above. We'll respond to any review comments promptly.
Common questions
What's the difference between a perc test and a soils report?
They answer different questions. A soils report (geotechnical investigation) tells your engineer how strong and stable the ground is — whether it can carry a foundation, whether it will settle, shrink, or swell, and how it must be graded and compacted. A percolation test measures how fast water soaks into the ground, which determines whether a septic system will work on your lot and how large the leach field or seepage pit must be.
If you're building on a lot with no sewer connection, you may need both. See the side-by-side comparison on our homeowners page.
How much does a perc test cost?
Percolation testing costs depend on the type of test the county requires for your lot (shallow pit tests for a leach field, or a deep boring for a seepage pit), how many test locations are needed, and whether a drill rig is required. Across Southern California, a residential perc test and report commonly runs in the low-to-mid thousands of dollars. Titan's pricing: [NEEDS FROM MOHAMMED: Titan's standard residential perc-test fee or range]. We'll give you a fixed written quote once we know the lot and the system type.
Do I need to be home on the day of the site visit?
Usually not. We need clear access to the area where the work will be done, a gate code or unlocked gate if the lot is fenced, and the location of any known underground utilities, septic tanks, or irrigation lines. We call Underground Service Alert (DigAlert, 811) before any drilling. Most homeowners are at work while we're there; we'll call you when we arrive and before we leave.
What areas do you serve?
We're based in Lancaster and work throughout the Antelope Valley: Lancaster, Palmdale, Rosamond, Quartz Hill, Littlerock, Lake Los Angeles, and the surrounding unincorporated areas of northern Los Angeles County. If your project is outside the valley, call us anyway — we'll tell you if we can serve it well or refer you to someone who can.
Building where there's no sewer?
Send us the APN or address and how many bedrooms you're planning. We'll tell you what testing the county will want and give you a fixed price.