What Is a Percolation Test and Why Do I Need One?
Percolation tests, often referred to as “perk tests” by the experts, can be a confusing term for those that are not familiar with the world of septic systems (i.e. most people). As a property owner the process of finding and purchasing a piece of land is already overwhelming, and the next step of designing and installing a septic system brings a host of high-cost variables and technical jargon that can cause considerable stress on a homeowner.
At Standard Septic, we seek to create confident customers by answering the most common questions posed by those we serve. In this article we are going to explain in laymen's terms what a percolation test is, why you need one, what you can expect to pay, and who is licensed to perform the test.
What Is A Percolation Test?
In the most basic terms: a percolation test is a measure of how quickly water drains through soil. Specifically, a perk test is performed to assess the absorption rate of soil in an area where a septic system installation has been proposed. Before any septic system can be installed in the ground, the soil's properties need to be evaluated to ensure proper waste management.
Properties like soil composition, drainage rate and presence of bedrock or groundwater all need to be taken into consideration when designing a septic system. A percolation test is the industry standard for collecting this information.
How is a Percolation Test Performed?
BC Engineering Group in Sonoma County, California has assembled an easy to understand description of how a percolation test is performed:
Locate soils that are suitable for septic development. This process includes reviewing soil test pits to evaluate the subsurface soils and conditions. The presence of groundwater or plastic soils, like clay, are typically considered limiting conditions.
Percolation test holes are installed at various depths depending on soil conditions observed.
Perforated pipes are installed into each percolation test hole and surrounded at the bottom of the pipe with 12” of pea gravel.
The percolation test holes are pre-soaked with water the day prior to the percolation test. This is to provide the soils with a typical level of saturation.
The day of the percolation test, which follows the day of pre-soaking per step #4, each pipe is filled with water to the pea gravel and the time of filling is recorded for each hole.
After one hour has passed, the water level is measured from the top of the pipe and recorded. This process is repeated for six hours; refilling the pipe to the pea gravel whenever the water level drops to within two inches from the bottom of the test hole. If a test hole runs dry after the first hour, refill to the pea gravel and take readings every ten minutes for two hours, also refilling the pipe to the pea gravel whenever the water level drops to within two inches from the bottom of the test hole.
Calculations for the percolation rate take place after the test is run. Divide the time intervals by the corresponding drop in water level to calculate the percolation rate in units of minutes per inch for each hole.
Although there are some differences in the soil composition and regulatory agencies of septic systems in Santa Barbara and San Luis Obispo counties, the general principal is dedicated by the California Onsite Wastewater Treatment System (OWTS) Policy produced by the California Water Boards
Why Do I Need A Percolation Test?
A percolation test is a crucial component in the process of septic system design. You will not be able to install a septic system on your property without proof of successfully completing a percolation test. Santa Barbara and San Luis Obispo counties both have dedicated agencies that are heavily involved in oversight of waste management, and will not issue a permit without passing a percolation test.
Although this might seem like unnecessary red tape that is holding up your project development, it's important to understand why you need this test. If the soil drains too quickly, the wastewater will not have time to break down properly before it escapes. And if this soil drains too slowly, it can cause your septic system to back up or wastewater to come up out of the ground. Both of these scenarios are disgusting and expensive.
Percolation tests are just as much about keeping the individuals on your property from becoming seriously ill as they are about being environmentally friendly.
Who Can Perform A Percolation Test?
The California On-Site Wastewater Treatment Systems policy states:
“Qualified professional” means an individual licensed or certified by a State of California agency to design OWTS and practice as professionals for other associated reports, as allowed under their license or registration. Depending on the work to be performed and various licensing and registration requirements, this may include an individual who possesses a registered environmental health specialist certificate or is currently licensed as a professional engineer or professional geologist. For the purposes of performing site evaluations, Soil Scientists certified by the Soil Science Society of America are considered qualified professionals. A local agency may modify this definition as part of its Local Agency Management Program.
If you aren't one for deciphering legal code (who is?) here's a translation in standard English:
California OWTS policy authorizes the following professionals to perform perc tests:
Licensed Engineer
Licensed Geologist
Certified Soil Scientists
Registered Environmental Health Specialists (REHS)
It is important to note that variances in the OWTS can occur among municipalities. Standard Septic Design operates exclusively in northern Santa Barbara and San Luis Obispo counties. The only difference in adherence to state policy between these counties regarding percolation tests is that an REHS is only authorized to perform these tests in SLO, and not in Santa Barbara.
Although Standard Septic Design (operating with an REHS) cannot perform a perc test in the county of Santa Barbara, we partner with many local, reputable engineers and soil scientists to perform that service for you.
How Much Does A Percolation Test Cost?
When you're calling around and collecting quotes for perc tests there can be a wide range that is frustrating, not to mention confusing. This variance is due to the fact that septic system design and installation hinges on several dynamic factors.
Factors that can affect cost
Type of wastewater: Whether your property will be producing domestic, commercial, or industrial waste will affect the price of your test.
Number of holes required: Santa Barbara county requires a minimum of 3 holes, while San Luis Obispo requires a minimum of 4 holes.
Number of tests required: If your initial percolation tests fail, the customer will need to have the test performed again at a new site. Because these tests require 24 hours before results can be determined, failed tests will also incur the cost of equipment being brought back on another day.
Soil type: Lighter, sandier soils provide for easier excavation and therefore reduce time spent on the job.
Site Access: If there are no roads, or other factors limiting equipment access to the site, then there is an additional cost to create access.
Standard Septic's Pricing
Our price at Standard Septic for percolation tests starts at $2,000. This price includes:
Approximately half a day of heavy equipment use, which includes the operator's time
Two days of the testing technician's time
A preliminary site walk with the owner of Standard Septic, Joel Schwartz to assess the location, meet the property owner, and answer questions.
Our Commitment to You
We are a family owned business that strives to be transparent in our pricing because we know how valuable a family's time and money is. Even if you decided to have your perk test and septic design performed by another company, this article can help to arm you with the information needed to make the choice that is right for you.
Our site walk and assessment is always done free of charge, and is a great opportunity to talk one on one with the company's owner and get the opinion of an experienced Registered Environmental Health Specialist on how to proceed with your project.
We look forward to hearing from you. Reach out to us today for a free consultation!
