Septic Systems (OWTS) (Health)

Septic Documents - Now Available Online

We have recently added the ability to locate and view septic documents on Larimer County's property records page. These documents can be viewed by searching for and selecting a property, and pulling up the 'Building Info' tab. If Larimer County has the septic documents on file, they will be linked there and can be viewed online.

Transfer of Title

2025 OWTS Application (169.74 KB)

2025 OWTS Application - Apply online.
This link will take you to our application portal for OWTS permits. Please note: first-time users will be asked to create an account.

A septic system, also called an on-site wastewater treatment system, is a self-contained system used to treat wastewater, usually in rural areas.

It typically includes a septic tank, which holds wastewater from drains and allows solids to settle at the bottom, and a network of pipes that spread the liquid waste underground in a leach field. The system filters the wastewater through the soil to clean it before it can reach drinking water wells or surface water.

State and county laws require you to get a permit from the Department before building or fixing a septic system.

Septic Fees

Permit Fees Effective January 1, 2025

Please see 2025 Environmental Health Fees (OWTS fees)

Septic Permit Instructions

Download the OWTS Permit Application Instructions as a PDF

Permit Types

New System: Needed for new construction or new systems serving extra buildings like guest houses, garages, or barns, if a sewer connection isn't available within 400 feet.
Major Repair: Needed for repairs that involve replacing, expanding, or changing the soil treatment area.
Minor Repair: Needed if you're replacing a septic tank.
Sealed Vault: Needed for installing or fixing sealed vaults, composting toilets, vaulted privies, or similar systems. Check the "Limited Use Wastewater Systems" guidelines for details.
Remodel or Upgrade: Needed when upgrading the soil treatment area for home additions or finishing basements that add bedrooms.
Site Evaluation: Needed only if test pits must be checked before applying for a permit.

Application Process

You need a soil test on your property before applying for an OWTS permit. The soil test will include one of the following:
1. Percolation testing for leakages and two soil test pits, or
2. Two soil test pits must be dug in the area of the proposed soil treatment area.
  -The test pits must stay open so Larimer County can inspect them during the application process. To keep the area safe, cover the pit openings with fencing, stakes, or other safety measures. If the pits need to be covered before you apply for a permit, you can request a site evaluation, but there will be an extra fee for this.
Fill out an OWTS Permit Application. You must include a copy of the following:
1. Soils test report
2. Design document
3. Plot plan
4. Engineer's design (if necessary).
You can submit your application and documents online or drop them off at the Department offices in Fort Collins or Estes Park. The addresses are listed at the bottom of this page.
Permit fees for each type are shown at the top of the application form. You’ll need to pay the fee when you submit your application.
The permit fees are listed at the top of the application form. You need to pay the fee when you apply.
For a New System permit, you need to include a soil report and a sketch plan with your application. The sketch plan shows basic calculations for the system and how it will be installed. This can be part of the soil report or submitted separately for simple, non-engineered systems.

A professional engineer must design the system if any of the following apply:

The soil percolation rate is outside the range of 5 to 60 minutes per inch.
The soil type is 0, 3A, 4, 4A, or 5.
The depth to bedrock or high groundwater is 4 feet or less below the surface.
The system uses pressure distribution.
The soil treatment area is on a slope of 30% or more.

You need to include a plot plan with your application for all permit types (see the example on the next page). The plot plan can be hand-drawn but must show the property lines, existing buildings, the area where the system will go, and the approximate location of soil tests (like percolation tests or soil test pits).
After you apply for the permit, Department staff will visit your property to inspect the site, check the test pits, and review the soil report. Make sure the site is marked with the address and that the test pits stay open for inspection. Use fencing, stakes, or other safety measures to keep the test pits secure and prevent accidents. During winter, inspections might be delayed because of the weather.
If your application follows Larimer County OWTS rules and the site inspection is approved, you’ll get your permit about 5 days after submitting your application. During the busy building season, it might take longer.

Notes

The permit will show the minimum required size for the tank and soil treatment area. Be sure to read the permit before starting construction to check for any specific details or extra inspections needed for your project.
You might not need a soil report for a Major Repair permit if there’s already soil testing information for the property and a site inspection shows that groundwater or bedrock is more than 4 feet below the surface.
The size of the septic system depends on how many bedrooms are in the home and the results of the soil test. Clay-like soils usually need a larger treatment area than sandy soils. If you plan to finish a basement or add rooms that could increase the number of bedrooms later, it’s a good idea to size the system for the future total number of bedrooms. Adding extra capacity during the original construction is much cheaper than upgrading the system later.

Sample Plot Plan

Provide a plot plan on a separate 8-1/2" x 11" sheet showing the following, the plot plan does not need to be to scale:

Location of the proposed OWTS;
Existing or proposed structures, wells (including neighbors), driveways, etc.;
Slope of property;
Location of soils test pits.

Site Evaluations for New Onsite Wastewater Treatment Systems

Site Evaluation Application This link will take you to our MyHD portal. Please note: first-time users will be prompted to create and account.

Since June 4, 2018, all applications for a new on-site wastewater treatment system must include an inspection of two test pits as part of the site and soil evaluation. You can also submit results from percolation tests, but these must be done along with the test pit evaluation. The test pits must stay open for Larimer County to inspect and can be inspected before applying for a permit using a specific form.

You’ll only need to pay an extra fee for a site evaluation if the test pits are dug before applying for a permit and need to be filled in immediately. Otherwise, you can secure the test pits with fencing, stakes, or similar methods, and they will be inspected during the permit application process without extra fees.

If you request a site evaluation, you’ll need to schedule a test pit inspection, which takes at least 5 business days to arrange.

Soil test pits must be constructed per the following Site & Soil guidelines;

You need at least two test pits in the area where the soil treatment system is planned. The pits should generally be 40–50 feet apart.
Each pit must be dug 8 feet deep, or until you hit groundwater or bedrock if they’re closer to the surface. The pit should have a flat area (bench) at 4 feet deep and slope back to the surface at a 45-degree angle to allow entry to the bench.
The test pits must stay open for inspection by Larimer County and the soils engineer or system designer.

Find a Licensed Professional

Search for Licensed Septic Installers and Cleaners

Septic System Permit Records

Septic System Permit Record Request

Use this form to request records for an On-Site Wastewater Treatment System (septic system) permit. The results will be emailed to you. For the best search results, include the property’s physical address and parcel number. If you only have one, a search can still be done. Adding extra details, like the lot and filing, subdivision, or current/previous owner, can help improve the results.

Keep in mind that not all properties have a permit. Homes built before 1973 often don’t have permit records unless the system was repaired or upgraded after 1973. If you find a record on a “Non-Permitted Septic System” card, it’s based on information from the owner, cleaner, or installer and doesn’t mean a permit was issued by the Department.

Requests submitted through this form are reviewed during regular business hours, Monday to Friday, 8 a.m. to 4:30 p.m. (except holidays). It may take up to 3 business days to process your request.

General Construction Guidelines for New and Repair Installations

Guidelines for OWTS Installations

Here’s a summary of common questions about construction requirements and code changes that came with Larimer County’s adoption of Colorado’s Regulation 43 in June 2018.

Tank Lids and Access Risers
Access risers must be installed up to ground level on all tank lids, distribution boxes, and other parts that need to be inspected or maintained. Lids must be watertight and securely fastened with screws, bolts, chains, or be heavy enough (over 59 pounds) to stay in place.

System Dimensions

Standard gravity-style systems can be up to 12 feet wide and 100 feet long. If more space is needed, multiple beds can be installed with at least six feet of undisturbed soil between them.
The system should be no deeper than 48 inches below the ground (to the bottom of the gravel or chambers). The permit will specify if the system needs to be shallower to maintain enough distance from bedrock or groundwater.

Distribution Boxes
If a distribution box (d-box) is used, flow equalizers must be installed on the outlet lines to adjust flow, and the d-box must have a watertight riser to grade for access.

Piping type, Bedding, and Clean-outs

Piping must be at least 4 inches wide, made of SDR 35 material, and buried 12 inches below the ground. It should have a slope of at least 1/8 inch per foot (1%) from the building to the septic tank. A slope of 1/4 inch per foot (2%) is recommended. Pressure-rated SCH 40 pipe is required for pressure distribution systems and when the pipe runs under driveways.
When installing gasketed pipes, make sure the bell ends are on the uphill side. To connect the building sewer to the foundation, use glued fittings or flexible couplers with shear rings or guards.

Piping bends should be limited to 45 degrees or smooth 90-degree turns. It's better to use two 45-degree fittings to turn 90 degrees in the building sewer (from the house to the tank).
You must have a cleanout within 5 feet of the building, for every 100 feet of the sewer line, and at every bend greater than 45 degrees, unless there’s already a cleanout within 40 feet upstream.
Before backfilling, the pipe must be placed in material free of rocks or large clods. Using sand or squeegee material is recommended. The tank inlet and outlet should be backfilled and compacted to support the pipe before installation.

Trench Style Systems

When chambers are installed in trenches, they must be in a single row. For gravity systems, the row can't be longer than 100 feet, and for pressure-dosed systems, it can't be longer than 150 feet. There should be at least 48 inches of undisturbed soil between rows, and each row must have an observation port at the end. Trench-style systems require fewer chambers than bed systems.

Construction Guidelines for Limited Use Wastewater

Limited use Wastewater

Download the Limited Use Wastewater Information as a PDF

Vault: This is a large tank that holds at least 1,250 gallons of wastewater. It needs to be sealed tightly to prevent leaks and should have a warning system to let you know when it's getting full so that it can be emptied.

Vaulted Privy: This is a smaller tank, at least 400 gallons, made of concrete, plastic, or fiberglass. It has an outhouse built on top for use as a bathroom.

Composting Toilet: This is a toilet that doesn't use water. It breaks down waste using natural processes to reduce it.

Portable Chemical Toilet: This is a temporary toilet that you usually see at construction sites or events. It's a self-contained unit that can be moved around easily.

Graywater - Wastewater generated from lavatory sinks, showers, and laundry. Excludes wastewater from kitchen sinks and toilets.

What is a limited use wastewater system?
Limited use wastewater systems include vaults, vaulted privies, composting or incinerating toilets, and portable chemical toilets. These systems are designed for properties that produce very little wastewater or for properties that can’t fit a full on-site wastewater treatment system (OWTS) with a soil treatment area.

Dwellings built as cabins without plumbing and hauling or hand carrying their primary source of water, RVs used on properties seasonally, and semi-permanent campsites are the primary users of limited use wastewater systems.

When can a limited use wastewater system be used?
These systems are only allowed for seasonal or short-term use homes, properties that can’t have a full onsite wastewater treatment system, areas where a full system can’t be installed, or when water is hauled or carried by hand.

Maintaining these systems can be expensive because vaults or holding tanks need to be pumped out often. Limited use wastewater systems are not allowed on properties that are or could be used for full-time living, especially if the water comes from a well or public supply, unless a full onsite wastewater system isn’t possible or is prohibited.

Can a vault be installed for a cabin or seasonal dwelling?
A vault, vaulted privy, or composting toilet can be used if the building is considered a cabin under the Larimer County Land Use Code and Building Department rules, and it has no plumbing or the water is hauled or carried to the site. However, these systems are costly to maintain long-term, so a full wastewater system is recommended.

For homes, cabins with water from a well or public system, or cabins converted to homes, a full onsite wastewater system must be installed unless the property can’t support a full onsite system with a soil treatment area. Simply using the property seasonally or part-time is not enough to justify using a limited wastewater system.

Can graywater be disposed of on the ground?

No, graywater from showers, laundry, or sinks must be treated and disposed of as wastewater. Larimer County OWTS Regulations prohibit running pipes from RVs or homes directly to the ground.

Graywater contains bacteria, viruses, soaps and detergents, as well as other contaminants that can impact groundwater and surface water, potentially causing contamination to drinking water wells, lakes, and streams.

When is a permit required?
You need a permit before installing a limited use wastewater system. For new construction, you must plan how wastewater will be managed before getting a building permit. If the land is vacant, you must apply for a permit before installing a vault or vaulted privy.

Limited use wastewater systems during construction
Portable chemical toilets are only allowed on properties during the construction of a home or in emergency situations. Alternatively, you can install a vault, septic tank used as a vault, or a full septic system to serve temporary living quarters until construction is finished.

Construction Guidelines for Pumps, Floats, and Controls

Download the Pumps, Floats, and Controls File as a PDF

Pressure Distribution to a Soil Treatment Area:

Designs for pressure distribution systems must include:

Pipe diameter for transport lines and laterals.
Orifice size and spacing.
A minimum 30 inch residual head for holes larger than 1/8” and 60 inch residual head for 1/8” holes.
Dose size and frequency.
Pump information, minimum gallons per minute and total dynamic head.

Piping for pressure distribution may be hung in the top of chambers or placed on the floor. Orifices must be directed upward if using chambers with drainage holes at either end of the lateral line or alternative spacing to allow piping to drain between doses.

If used with rock and pipe, the lateral piping must have at least 6" of gravel placed beneath the pipe and 2" above the pipe.

Cleanouts are required at the end of each line in a system that uses pressure distribution. You can use valves, like the one shown below, or threaded caps for this purpose.

Systems utilizing a pump to lift wastewater to a soil treatment area at a higher elevation or to provide pressure distribution must meet Section 43.9.I of the Larimer County On-Site Wastewater Treatment System Regulations. The following is a summary of the requirements:

The high-level alarm and pump control floats should be attached to a separate stem from the pump outlet piping. This way, the pump can be removed and serviced without changing the float settings.
The discharge line must be protected from freezing by adding a weep hole in the outlet piping, which directs water into the tank or back through the pump. The piping should slope back toward the tank or soil treatment area to allow drainage.
A quick disconnect or union must be installed on the pump discharge line within 18 inches of the tank's access lid. This lets you remove the pump without cutting the outlet line or reaching inside the tank to make repairs.
All electrical connections should be made outside of the tank and riser. Run the electrical connections for the pump and floats outside the riser to prevent corrosion, and leave extra wire so components can be removed easily.
For pressure distribution, the control panel must track pump run times and the number of pump cycles. It should also have a switch that allows you to manually operate the pump. The control panel must include both an audible and visual alarm and have a disconnect switch within sight of the pump chamber.

Additionally,

Control panels must be UL listed and have separate breakers for the pump and high water alarm.
The pump must be placed in a screened vault, or an effluent screen must be installed in the chamber before the pump.

Construction Guidelines: Site and Soil Evaluation Requirements

The site and soil evaluation is an important step in the permitting process for on-site wastewater treatment systems (OWTS). It helps determine if the site and soil are suitable for installing an OWTS, how large the soil treatment area should be, and if there are any nearby features like lakes, creeks, irrigation ditches, or wells that might need to be considered to prevent contamination.

Starting June 4, 2018, all applications for a new on-site wastewater treatment system must include an inspection of two test pits as part of the site and soil evaluation. These evaluations must be done by a professional engineer or under their supervision.

Soil test pits must be constructed per the following guidelines;

The test pits must be dug in the area where the soil treatment system will go. They should be 8 feet deep unless groundwater or bedrock is found earlier. The hole should be benched at 4 feet below ground and sloped at a 45-degree angle to allow safe entry.
The test pit must stay open for inspection by Larimer County and the engineer or system designer. It should be secured with fencing, stakes, or other safety measures.
If the test pits need to be filled in before applying for a permit, you can request a Site Evaluation, but this requires a separate inspection fee. If percolation testing is done, two test pits must also be evaluated.
The results of the test pit evaluation and any percolation tests must be included with the OWTS application.

A soils report is required for all systems. It must include calculations for each component, a proposed layout of the soil treatment area, the tank depth, and the dimensions of trenches or beds. It should also detail the placement of distribution boxes, manifolds, or other parts of the system. For standard systems, this information can be part of the soils report or submitted separately.

If any of the following conditions apply, the system must be designed by a professional engineer:

The soil percolation rate is not between 5 and 60 minutes per inch, or the soil is classified as types R, 3A, 4, 4A, or 5.
Bedrock or seasonally high groundwater is 4 feet or less below the ground surface.
The system uses pressure distribution.
The soil treatment area is on a slope of 30% or more.

Percolation tests are not needed if the engineer or system designer evaluates two soil test pits. However, if percolation tests are done, they must follow the rules in the regulations. Two test pits must still be dug, even if percolation testing is not performed.

Here’s how to conduct a percolation test for a soil treatment area:

Dig Test Holes:
- Dig at least three holes, 8–12 inches wide, in the area where the soil treatment system will go.
- Make the holes 6–18 inches below the proposed infiltration surface. If the depth is unknown, dig holes at different depths (up to 5.5 feet deep).
Prepare the Holes:
- Add 2 inches of sand or gravel to the bottom of each hole.
- Presoak the holes with water for 24 hours before starting the test.
Conduct the Test:
- Fill the hole with water to 6 inches above the sand or gravel.
- Measure how far the water drops over 30-minute intervals for 4 hours, refilling as needed to keep the water level at 6 inches.
- Use the water level drop from the last 30-minute interval (not the average of all drops) to calculate the percolation rate.
Special Cases:
- If the water drop rate stabilizes after 2 hours with three consistent measurements, you can stop the test early.
- In sandy soils where all water drains out within 30 minutes (after presoaking), take readings every 10 minutes for 1 hour.

A one foot width by three foot length trench in the ground.

On-Site Wastewater Treatment System Regulations

2024 Larimer County Onsite Wastewater Treatment Systems Regulations

Septic Systems

Questions? Call OWTS at (970)498-6775

Search for Septic Documents by property address
On the property details page, under the Building Info tab and Property Attributes & Descriptions heading (Attribute: Sewer)

Septic Systems (OWTS)