Davis Septic Design

Welcome to your complete guide for maintaining a healthy septic system in King County. At Septic System Design, we are committed to providing our community’s homeowners especially our respected veterans and seniors with the knowledge and support needed for proper septic care. This page covers core advice, a seasonal calendar, and details on our special support programs designed to make essential maintenance affordable and straightforward.

Core Maintenance Advice

A little knowledge goes a long way in preventing costly septic system problems. These fundamental tips are the cornerstone of a healthy system.

How often should you pump septic systems?

For the average household, we recommend professional septic pumping every 3 to 5 years. However, factors like the number of people in your home, your tank’s size, and your daily water usage can affect this frequency. Regular pumping is the most critical preventative measure you can take to avoid solid waste buildup, which can lead to drain field failure.

What products are septic safe?

The bacteria inside your septic tank are essential for breaking down waste. Using the wrong products can harm this delicate ecosystem.

• Septic-Safe: Use biodegradable soaps, mild detergents, and toilet paper labeled “septic-safe.”
• What to Avoid: Harsh chemicals, bleach, antibacterial soaps, “flushable” wipes, grease, coffee grounds, and non-biodegradable items will either kill beneficial bacteria or create clogs.

Detecting slow drains and early warnings

Your home’s plumbing will often give you clues before a major septic emergency occurs. Be alert for these early warning signs:

• Gurgling sounds from toilets or drains.
• Water draining slowly from sinks, showers, or tubs.
• Unpleasant odors near the tank or drain field.
• Unusually green or soggy patches of grass over the drain field.

Seasonal Maintenance Calendar

Your septic system’s needs can change with the King County weather. Follow this seasonal guide to stay ahead of potential issues.

Winter prep tips for our local climate

King County winters are more wet than frozen, but preparation is still key. Insulate exposed pipes and tank risers with a layer of mulch or a septic blanket to protect them from occasional frosts. Most importantly, schedule any necessary pumping before the heavy rains begin to prevent overwhelming a system surrounded by saturated ground.

Summer usage care

Summer often brings guests and increased water usage. Be mindful of your system by spreading laundry loads throughout the week instead of doing them all in one day. Ensure lawn sprinklers are not watering the area over your drain field, as excess water can hinder its ability to process waste.

Annual inspection checklist

Once a year, perform a quick visual inspection:

1. Walk around your tank and drain field, looking for wet spots or odors.
2. Check for any visible leaks or cracks in the tank risers.
3. If you have an effluent filter, check if it needs cleaning.
4. Schedule a professional inspection to have an expert assess the tank’s sludge levels and overall system health.

Veteran & Senior Support Programs

We are proud to offer dedicated programs to support the veterans and seniors in our community.

What discounts exist for vets?

As a small thank you for your service to our country, we offer a special discount on our septic maintenance and pumping services. Please mention your veteran status when you call to schedule your appointment so we can apply this to your invoice.

How to qualify for senior pricing

To help make essential home maintenance more affordable, we offer senior pricing for King County homeowners aged 65 and older. This discount is our way of supporting the residents who have built and strengthened our community over the years.

How to schedule service

Booking an appointment is easy. Call us directly at 425-248-1140 or fill out the contact form on our website. Our team will find a time that works for you and make sure to include your veteran or senior discount right from the start.

A failed septic inspection can feel like a sudden and expensive roadblock, especially if you’re in the middle of selling your home. The report arrives with technical jargon and a “not functioning” status, leaving you with a flood of questions about cost, timelines, and what to do next.

While a failed inspection is a serious issue that must be addressed, it is a solvable one. Think of it not as a final verdict, but as a diagnosis with a clear path to treatment. This guide will walk you through the essential steps to recover from a failed septic inspection in Washington State, get your property back into compliance, and keep your home sale on track.

Understanding the Inspection Failure

The first step is to move past the initial shock and become informed. Your inspection report is the key—it’s a diagnostic tool that outlines exactly what went wrong.

Why did the inspection fail?

An inspection doesn’t just result in a “pass” or “fail.” A certified inspector is required to document specific observations. Your report should detail the precise reasons for the failure. Carefully read this section, as it will be the foundation for the repair or redesign plan. It will point to a problem with a specific component (like the tank or drain field) or with the system’s overall compliance.

Common failure reasons in King/Snohomish Counties

In our region, with its unique geology and mix of older and newer homes, we see recurring themes in inspection failures:

• Drain Field Saturation: This is the most common major failure. It means the soil surrounding the drain field is saturated with wastewater and can no longer absorb it. This can be caused by age, dense glacial till soils that have become compacted, or hydraulic overload from increased water usage. You may notice spongy ground or foul odors in the yard.
• Component Failure: The issue may be a single part. Common examples include a cracked septic tank, collapsed or root-infested pipes leading to the drain field, or a malfunctioning pump in an engineered system.
• Code Non-Compliance: The system may be functioning, but it violates current health codes. This is frequent in older properties where a deck, patio, or addition was built over the tank or drain field, or the system is too close to a well or property line.
• Severe Lack of Maintenance: If a tank hasn’t been pumped in over a decade, solid waste can flow into the drain field, permanently clogging the soil and causing irreversible failure.

Repair & Redesign Options

Once you know why the system failed, you can explore solutions. These fall into two broad categories: minor repairs or a full redesign.

Cost estimates: minor repair vs. full redesign

The financial difference between these two paths is significant.

• Minor Repair Cost: ~$1,500 – $5,000 This applies to fixing a single component. Examples include replacing a broken baffle in the tank, installing risers for better access, replacing a failed pump, or hydro-jetting a specific clogged pipe.
• Full Redesign & Replacement Cost: ~$25,000 – $50,000+ This is required for a failed drain field. The cost is high because it’s a major construction project that includes a licensed designer’s fees for soil testing and plans, county permit fees, and the contractor’s costs for excavation, a new tank, a new drain field (which may need to be a more expensive engineered system like a mound or OSCAR), and final grading.

Who handles the repair design process?

The nature of the failure dictates who you need to call.

• For minor repairs like a pump replacement, a qualified septic service technician can often handle the work.
• For any major repair involving the drain field or a full system replacement, a Licensed Septic Designer is required by law. The designer will assess the site, perform soil tests, create the official plans for the new system, and manage the permit application process.

How long until it’s remedied?

• Minor Repair: Typically 1 to 5 days.
• Full Replacement: This is a multi-stage process. A realistic timeline is 1 to 3 months from your first call to a designer to the completion of the installation. This includes time for site evaluation, design, permit review by the county (which can take several weeks), and the actual construction.

Re-inspection and Sale Readiness

If you’re selling your home, the goal is to get a clean bill of health for your septic system as efficiently as possible.

How to pass a re-inspection

Passing the re-inspection is straightforward. After the repair or replacement work is completed under an approved permit, the local health department inspector will visit the site. Their job is to verify that the installation matches the approved design plans exactly. Choosing a reputable designer and a qualified installer is the key to ensuring the work is done right and passes the first time.

Can you sell a home with septic issues?

Yes, but it adds a significant complication to the transaction. You have two main options:

1. Fix It First (Recommended): The cleanest approach is to complete the repairs or replacement before closing. This removes all uncertainty for the buyer and their lender, leading to a smoother transaction.
2. Negotiate the Cost: If time is too short, you can get firm bids from a designer and installer for the full cost of the replacement. This amount can then be credited to the buyer at closing or held in escrow for them to manage the repair after they take possession. Many buyers are wary of this, as they are taking on a major construction project right after moving in.

Often, these negotiations hinge on a clear understanding of the project’s scope. For a closer look at what’s involved, you can review our guide on septic maintenance and common repair solutions.

Timeline & Permit Path

Any major repair requires a new permit from your local health department.

Permit submission process

This is not a simple form. A permit application for a major repair or replacement is a detailed package prepared by your septic designer. It includes:

• The results of new soil logs.
• A professional design showing the layout and specifications of the new system.
• All required county application forms and associated fees.

Coordination with local health departments

An experienced local designer is your greatest asset here. They understand the specific codes and preferences of reviewers at King County Public Health or the Snohomish Health District. Their familiarity with the process and personnel helps ensure a complete and accurate application is submitted, which is the best way to avoid unnecessary delays and requests for more information.

Buyer/Seller FAQ

How much will the repair cost?

Expect to pay between $1,500 and $5,000 for minor, single-component fixes. For a full drain field replacement, budget for $25,000 to $50,000+, depending on the site and the type of system required.

How long until the issue is resolved?

Minor repairs can often be done within a week. A full replacement is a 1 to 3-month process that includes design, permitting, and installation.

What should I expect from a septic designer?

A professional designer will manage the technical aspects of the project. You should expect an initial site consultation, soil testing, a clear explanation of your system options, a detailed design plan for the chosen solution, and full management of the county permit submission process. They are your expert guide from diagnosis to cure.

For homeowners in King and Snohomish counties, the ground beneath their feet tells a story. It’s a story of ancient glaciers, rich deposits, and dense, compacted soils that can make installing a standard septic system a significant challenge. When a septic system fails here, the solution isn’t just about replacing a tank; it’s about understanding the unique soil science of your property and choosing a technology engineered to work with it.

This guide will walk you through the critical link between local soil types and your septic system choices. We’ll then go behind the scenes on a real project, following the installation of a modern OSCAR-II system from the initial soil test to the final performance check, showing you how today’s technology solves yesterday’s problems.

Soil Science & Septic Design

Before any septic design begins, we must first “read the land.” In Washington, the soil itself is legally considered the final component of the treatment process. Its ability to safely filter and disperse wastewater dictates everything that follows.

How does soil type affect septic choice?

Your property’s soil acts like a natural filter and sponge. It needs to absorb treated wastewater (effluent) at a steady rate—not too fast and not too slow.

• If soil is too dense (like clay), effluent can’t soak in. It pools, surfaces in your yard, and causes a system failure.
• If soil is too coarse (like clean gravel), effluent can pass through too quickly without adequate filtration, potentially contaminating groundwater.

This “percolation rate,” along with the usable soil depth, determines whether you can use a simple, conventional gravity system or if you need an advanced engineered system to overcome the site’s limitations.

Reading soil logs—what to look for

A soil log is a professional report created by a licensed designer after digging a test pit. It’s the scientific basis for your septic design. Key things we look for include:

• Restrictive Layer: This is the most critical factor. It’s a layer of dense glacial till, hardpan, or bedrock that water cannot easily pass through. Its depth determines your vertical separation.
• Seasonal High Water Table: We identify this by looking for “mottling”—patches of rust-colored soil. This tells us the highest point groundwater reaches in the wet season. The bottom of your drain field must be a set distance above this mark to ensure it never gets flooded.
• Soil Texture: We document the layers of sand, silt, and clay, which informs the system type and size.

Gravel, clay, sand: pros and cons

The OSCAR-II System Explained

When a site has dense glacial till or a high water table, we need an engineered solution. One of the most effective and versatile options is the OSCAR-II system.

What is an OSCAR-II?

OSCAR stands for On-site Sand Coil Area Recharge. It is a low-profile treatment and dispersal system. An OSCAR-II unit consists of coils of drip tubing laid out on a bed of specialized sand medium. Effluent from the pump tank is slowly dripped onto the sand, which provides a final, high level of treatment before the water is gently absorbed into the native soil below.

Advantages over conventional systems

The OSCAR-II is a problem-solver. Its key advantages include:

• Handles Poor Soils: It’s specifically designed to work on sites with dense clay or shallow restrictive layers.
• Small Footprint: The treatment unit is compact, making it perfect for smaller lots or properties with limited space due to trees, outbuildings, or setbacks.
• Excellent Water Treatment: The sand medium provides robust filtration, making it an environmentally sound choice for protecting groundwater.

Suitability for local soil conditions

The geology of King and Snohomish counties was heavily shaped by the Vashon Glacier, which left behind vast deposits of highly compacted, dense till. This soil is notoriously difficult for conventional septic systems. The OSCAR-II directly addresses this challenge, making it possible to safely develop and repair homes on properties that would otherwise be unsuitable.

Step-by-Step Installation Walkthrough: A Woodinville Case Study

The Scenario: A homeowner on a 0.5-acre wooded lot in Woodinville had a failing septic system from the 1990s. Their yard had soggy patches, and a recent inspection confirmed the drain field was no longer functioning.

Step 1: Soil log testing and feasibility

Our first step was to dig two test pits. The soil log revealed just 18 inches of usable topsoil before hitting a dense, water-restricting layer of glacial till. This immediately ruled out a conventional system. Given the lot’s size and the homeowner’s desire to preserve several mature trees, a large mound system was not ideal. The OSCAR-II was identified as the perfect solution due to its small footprint and suitability for shallow soils.

Step 2: Permitting timeline and submittal

With the feasibility confirmed, we created a complete design package. This included the soil log data, detailed plans for the new tanks, the pump system, and the OSCAR-II unit specifications. The package was submitted to Public Health — Seattle & King County. Because the design was thorough and used a pre-approved, modern technology, the permit was issued in just under four weeks.

Step 3: Installation coordination with the contractor

Once the permit was in hand, we coordinated with the homeowner’s chosen certified installer. We held a pre-construction meeting on-site to walk through the design, stake out the exact locations for all components, and confirm the installation schedule. This ensures that the designer’s plan is executed precisely by the installation team.

Problem-Solving Mid-Project

Even with perfect planning, real-world construction can present challenges.

Typical delays and solutions

The most common installation delays are caused by weather and supply chain issues. Heavy rain can flood excavations, while specific components like pumps or control panels can sometimes have lead times. We mitigate this by ordering critical parts as soon as the permit is approved and by building buffer days into the installation schedule.

How installation challenges were handled

During our Woodinville project, an unexpected summer downpour occurred after the excavation for the new tanks was dug but before they could be installed. The hole partially filled with water.

Our Solution: The installer acted quickly. They used a pump to dewater the excavation, allowed it to dry for 24 hours, and then laid a fresh, stable base of crushed rock. This ensured the tanks were set on a solid, level foundation, preventing a minor weather event from turning into a major project delay.

Post-Install & Performance

The job isn’t done when the last patch of dirt is smoothed over. Proper maintenance is key to a long system life.

Service requirements and maintenance

An OSCAR-II is an advanced system that requires routine professional service. This includes an annual inspection by a certified maintenance provider to check the pump, floats, and electrical components, and to flush the drip lines. This is a simple, proactive step that ensures the system functions at peak performance for For homeowners in King and Snohomish counties, the ground beneath their feet tells a story. It’s a story of ancient glaciers, rich deposits, and dense, compacted soils that can make installing a standard septic system a significant challenge. When a septic system fails here, the solution isn’t just about replacing a tank; it’s about understanding the unique soil science of your property and choosing a technology engineered to work with it.

This guide will walk you through the critical link between local soil types and your septic system choices. We’ll then go behind the scenes on a real project, following the installation of a modern OSCAR-II system from the initial soil test to the final performance check, showing you how today’s technology solves yesterday’s problems.

Soil Science & Septic Design

Before any septic design begins, we must first “read the land.” In Washington, the soil itself is legally considered the final component of the treatment process. Its ability to safely filter and disperse wastewater dictates everything that follows.

How does soil type affect septic choice?

Your property’s soil acts like a natural filter and sponge. It needs to absorb treated wastewater (effluent) at a steady rate—not too fast and not too slow.

• If soil is too dense (like clay), effluent can’t soak in. It pools, surfaces in your yard, and causes a system failure.
• If soil is too coarse (like clean gravel), effluent can pass through too quickly without adequate filtration, potentially contaminating groundwater.

This “percolation rate,” along with the usable soil depth, determines whether you can use a simple, conventional gravity system or if you need an advanced engineered system to overcome the site’s limitations.

Reading soil logs—what to look for

A soil log is a professional report created by a licensed designer after digging a test pit. It’s the scientific basis for your septic design. Key things we look for include:

• Restrictive Layer: This is the most critical factor. It’s a layer of dense glacial till, hardpan, or bedrock that water cannot easily pass through. Its depth determines your vertical separation.
• Seasonal High Water Table: We identify this by looking for “mottling”—patches of rust-colored soil. This tells us the highest point groundwater reaches in the wet season. The bottom of your drain field must be a set distance above this mark to ensure it never gets flooded.
• Soil Texture: We document the layers of sand, silt, and clay, which informs the system type and size.

Gravel, clay, sand: pros and cons

The OSCAR-II System Explained

When a site has dense glacial till or a high water table, we need an engineered solution. One of the most effective and versatile options is the OSCAR-II system.

What is an OSCAR-II?

OSCAR stands for On-site Sand Coil Area Recharge. It is a low-profile treatment and dispersal system. An OSCAR-II unit consists of coils of drip tubing laid out on a bed of specialized sand medium. Effluent from the pump tank is slowly dripped onto the sand, which provides a final, high level of treatment before the water is gently absorbed into the native soil below.

Advantages over conventional systems

The OSCAR-II is a problem-solver. Its key advantages include:

• Handles Poor Soils: It’s specifically designed to work on sites with dense clay or shallow restrictive layers.
• Small Footprint: The treatment unit is compact, making it perfect for smaller lots or properties with limited space due to trees, outbuildings, or setbacks.
• Excellent Water Treatment: The sand medium provides robust filtration, making it an environmentally sound choice for protecting groundwater.

Suitability for local soil conditions

The geology of King and Snohomish counties was heavily shaped by the Vashon Glacier, which left behind vast deposits of highly compacted, dense till. This soil is notoriously difficult for conventional septic systems. The OSCAR-II directly addresses this challenge, making it possible to safely develop and repair homes on properties that would otherwise be unsuitable.

Step-by-Step Installation Walkthrough: A Woodinville Case Study

The Scenario: A homeowner on a 0.5-acre wooded lot in Woodinville had a failing septic system from the 1990s. Their yard had soggy patches, and a recent inspection confirmed the drain field was no longer functioning.

Step 1: Soil log testing and feasibility

Our first step was to dig two test pits. The soil log revealed just 18 inches of usable topsoil before hitting a dense, water-restricting layer of glacial till. This immediately ruled out a conventional system. Given the lot’s size and the homeowner’s desire to preserve several mature trees, a large mound system was not ideal. The OSCAR-II was identified as the perfect solution due to its small footprint and suitability for shallow soils.

Step 2: Permitting timeline and submittal

With the feasibility confirmed, we created a complete design package. This included the soil log data, detailed plans for the new tanks, the pump system, and the OSCAR-II unit specifications. The package was submitted to Public Health — Seattle & King County. Because the design was thorough and used a pre-approved, modern technology, the permit was issued in just under four weeks.

Step 3: Installation coordination with the contractor

Once the permit was in hand, we coordinated with the homeowner’s chosen certified installer. We held a pre-construction meeting on-site to walk through the design, stake out the exact locations for all components, and confirm the installation schedule. This ensures that the designer’s plan is executed precisely by the installation team.

Problem-Solving Mid-Project

Even with perfect planning, real-world construction can present challenges.

Typical delays and solutions

The most common installation delays are caused by weather and supply chain issues. Heavy rain can flood excavations, while specific components like pumps or control panels can sometimes have lead times. We mitigate this by ordering critical parts as soon as the permit is approved and by building buffer days into the installation schedule.

How installation challenges were handled

During our Woodinville project, an unexpected summer downpour occurred after the excavation for the new tanks was dug but before they could be installed. The hole partially filled with water.

Our Solution: The installer acted quickly. They used a pump to dewater the excavation, allowed it to dry for 24 hours, and then laid a fresh, stable base of crushed rock. This ensured the tanks were set on a solid, level foundation, preventing a minor weather event from turning into a major project delay.

Post-Install & Performance

The job isn’t done when the last patch of dirt is smoothed over. Proper maintenance is key to a long system life.

Service requirements and maintenance

An OSCAR-II is an advanced system that requires routine professional service. This includes an annual inspection by a certified maintenance provider to check the pump, floats, and electrical components, and to flush the drip lines. This is a simple, proactive step that ensures the system functions at peak performance for decades. The septic tank will still require pumping every 3-5 years, just like any other system.

This annual checkup is vital for ensuring decades of reliable performance. For more on what you can do as a homeowner between professional visits, read our guide on essential septic maintenance tips to protect your investment.decades. The septic tank will still require pumping every 3-5 years, just like any other system.

This annual checkup is vital for ensuring decades of reliable performance. For more on what you can do as a homeowner between professional visits, read our guide on essential septic maintenance tips to protect your investment.

As we move through 2025, Washington State is implementing one of the most significant updates to its on-site sewage system (OSS) regulations in years. Driven by a renewed commitment to protecting the ecological health of Puget Sound and other sensitive waterways, these new rules directly impact homeowners planning to install or replace a septic system.

While new regulations can seem daunting, they represent a critical step forward in environmental stewardship. For property owners, understanding these changes isn’t just about compliance. its about investing in a modern, efficient system that protects our shared natural resources and ensures a smoother, faster permitting process. This guide breaks down what you need to know about the 2025 WA septic code and how proper design is the key to success.

Key Regulatory Changes for 2025

The Washington State Department of Health, in coordination with county health departments, has rolled out targeted updates aimed at reducing nutrient pollution and better protecting groundwater.

What changed in the septic code for 2025?

The core of the 2025 updates focuses on reducing the impact of septic systems on the marine environment, particularly nitrogen pollution, which contributes to harmful algal blooms in Puget Sound. The key changes include:

• Stricter Setbacks: Increased mandatory distances between septic systems and shorelines.
• Nitrogen-Sensitive Zones: Formal designation of areas requiring advanced wastewater treatment.
• Enhanced Vertical Separation: Greater required depth between the bottom of a drain field and the water table.
• Permit Prioritization: A new streamlined process that favors environmentally superior designs.

New setback and environmental buffer rules near Puget Sound

One of the most impactful changes is the expansion of setbacks for properties near shorelines. For many areas bordering Puget Sound, the minimum setback for conventional drain fields has been increased, often from 100 feet to 150 feet or more from the Ordinary High Water Mark (OHWM).

This change creates a larger protective environmental buffer, allowing for more natural filtration and reducing the risk of contaminants reaching the water. For homeowners with limited space, this new rule makes thoughtful, compact system design more critical than ever.

Permit processing adjustments

To encourage the adoption of new technologies, many county health departments have adjusted their permit review process. Applications featuring compliant, advanced treatment systems that meet the new 2025 standards are often placed on a priority review track. This means that while a standard design might face additional scrutiny and longer wait times, a well-documented, environmentally-focused design can achieve approval significantly faster.

Septic Design and Shoreline Protection

The 2025 regulations place a heavy emphasis on the role of system design in protecting water quality. A simple septic tank and gravity drain field are no longer a one-size-fits-all solution, especially near the coast.

How septic design protects water quality

A conventional septic system is effective at removing pathogens but does little to reduce nitrogen levels. Effluent leaving the tank is high in nitrogen, which acts as a fertilizer for algae in the marine environment.

Advanced systems, however, use technology to significantly cut down on nitrogen. By introducing oxygen into the treatment process, these systems convert harmful nitrogen compounds into harmless nitrogen gas, which is then released into the atmosphere. This technology is at the heart of the new 2025 protection strategy.

Are ATU systems required near sensitive zones?

Yes, for many properties. Under the 2025 rules, if your property falls within a designated “Nitrogen-Sensitive Zone” (which includes large areas of the Puget Sound coastline), an Aerobic Treatment Unit (ATU) or another approved nitrogen-reducing technology is now mandatory for all new installations and most major repairs. A leading example is the NUWater BNR-600 ATU, a system we frequently design and recommend for its proven reliability and high performance in these exact environments.

Case Study & Compliance Examples

Navigating these new rules is best understood through real-world application. A professional designer’s role is to integrate these requirements into a seamless, functional plan.

Sample project near Puget Sound

Consider a recent project on a waterfront lot on Camano Island. The property’s existing 1980s-era system failed, and it was located only 75 feet from the shoreline. Under the old rules, a simple replacement might have been possible, but the 2025 code made that impossible.

The Solution: Our team designed a system using a compact NUWater ATU. The treated, sanitized effluent was then dispersed into a small, shallow pressurized drain field located 155 feet from the shoreline, fully complying with the new setback and water quality rules. The homeowner received a superior, long-lasting system, and the permit was approved on the priority track in under four weeks.

Regional workflow for designers and installers

The new workflow for a successful project in a sensitive area now looks like this:

1. Expert Site Evaluation: A designer conducts a thorough site and soil analysis with the 2025 rules in mind.
2. Compliant Design: The system is designed from the ground up to meet all setback, vertical separation, and nitrogen-reduction standards.
3. Priority Permit Submittal: The complete, compliant design package is submitted to the county health department for priority review.
4. Certified Installation: Once the permit is approved, the plans are handed off to a qualified installer who understands the specifics of advanced system installation.

Homeowner FAQs (AI Overview Style)

Here are quick answers to the most common questions we hear about the new regulations.

Do I need a special system near Puget Sound?

It is now very likely that you do. If your property is within several hundred feet of the shoreline or a connecting stream, the 2025 regulations will almost certainly require you to install an ATU or similar nitrogen-reducing system for any new construction or system replacement. A site evaluation by a licensed designer is the only way to know for sure.

How fast are permits processed?

Permit speed now heavily depends on your design. A design that just meets the bare minimum standards may face a standard review time of 8-12 weeks or longer. A design that proactively uses approved advanced treatment technology and is clearly documented can often be approved on the priority track in as little as 3-5 weeks. Because of this, we encourage homeowners to learn the early warning signs of septic failure and understand your repair options long before a small issue becomes a major emergency.

Expert Tips & Resources

Your best strategy is to be proactive and informed.

Tips to ensure permit approval

1. Hire a Local Expert: Work with a licensed designer who has proven experience navigating the 2025 code updates in your specific county.
2. Start Early: The days of fast, simple permits for shoreline properties are over. Begin the design and permitting process months before you plan to start construction.
3. Design for Compliance, Not the Minimum: Opting for a superior, compliant system from the start is the fastest and most reliable path to getting your permit approved.

Essential Resources

For the official text and guidelines, we always recommend consulting the source directly:

• The Washington State Department of Ecology provides overarching guidance on water quality protection.
• Your local County Health Department’s website will have the specific forms, fee schedules, and regulations for your area.

Receiving a notice that your septic system has failed its inspection is stressful. For homeowners in Snohomish County, with its unique soil compositions and strict environmental regulations, this news often brings a wave of questions about cost, complexity, and the best path forward.

But a failed system isn’t a dead end—it’s an opportunity to upgrade to a modern, reliable solution that protects your property value and the local environment. The two primary options you’ll face are a traditional conventional septic system and an advanced engineered system like OSCAR.

This guide provides a deep comparison to help you understand which system is the right choice for your failing septic system, your property, and your peace of mind.

OSCAR System Overview

When a conventional system isn’t an option, the OSCAR system often emerges as the leading solution. It is a highly effective, engineered system specifically designed for challenging properties.

What is an OSCAR system?

OSCAR stands for On-Site Sand Coil Area Recharge. It is a specialized, low-profile septic system that uses a drip dispersal method. Instead of relying on a large gravel-filled trench, an OSCAR system utilizes coiled drip tubing laid over a carefully prepared sand bed. This design allows for the slow, even, and highly treated distribution of effluent into the soil.

It was developed specifically for properties that cannot support a conventional gravity system due to common Snohomish County challenges like:

• Shallow restrictive layers of soil (hardpan or glacial till).
• Limited physical space for a large drain field.
• High seasonal water tables.

The OSCAR system is a fully recognized and approved technology in Snohomish and King counties and is frequently the go-to solution for difficult sites from Monroe to the foothills.

How long does an OSCAR last?

With a professional design from a team like Davis Septic Design, proper installation, and consistent maintenance, an OSCAR system can last 20 to 30 years or more. Its longevity is directly tied to diligent care, including routine inspections and pump-outs, using only septic-safe household products, and avoiding soil compaction over the drain field area.

Cost comparison: OSCAR vs. conventional

There’s no hiding it: OSCAR systems generally have a 15% to 30% higher upfront cost than conventional systems. This is due to the advanced design requirements, the complexity of the installation (which involves pumps, drip lines, and sand beds), and the use of specialized components.

However, the true value emerges over time. For a property with poor soil, a cheaper conventional system is at high risk of premature failure, leading to more costs down the road. An OSCAR system, while a larger initial investment, provides a reliable, long-term solution that equalizes in value by preventing future failures.

Conventional Septic System Basics

The traditional gravity-fed system is the most common type of septic system, and for the right property, it remains an excellent choice.

Traditional gravity systems – pros and cons

Pros:

• Lower Upfront Cost: It is the most affordable system to design and install.
• Simpler Design: With fewer moving parts, maintenance is straightforward.
• Widely Understood: Most septic professionals are familiar with its operation and repair.

Cons:

• Requires Good Soil: It is completely dependent on deep, permeable soil to function correctly.
• Site Limitations: Not suitable for properties with steep slopes, heavy clay soil, or high groundwater.
• Large Footprint: Requires significant space, making it difficult for smaller lots with tight setbacks.

When to repair vs. replace

After a failed inspection, the big question is whether you can repair your existing system or if a full replacement is necessary.

Repair might be an option if:

• The issue is a minor clog in the drain field or a problem with the tank itself.
• The surrounding soil still percolates well and the absorption area is structurally intact.

Replacement is likely required if:

• The drain field is fully saturated and no longer absorbs effluent.
• The septic tank is cracked, leaking, or structurally compromised.
• A Snohomish County health inspector has reviewed the site and mandates a full system redesign to meet current codes.

Pro Tip: If your property’s as-built drawing (CAD) is over 20 years old, the county may require a completely new design to comply with modern standards, even if the failure seems minor.

Soil & Site Compatibility

The single most important factor determining your septic system choice is your soil. A professional soil log is the only way to know for sure what your property can support.

What soil suits an OSCAR system?

An OSCAR system is the engineered solution for properties where conventional systems are not viable. It is ideal for sites with:

• Shallow or restrictive soils (less than 12 inches of usable soil depth).
• Dense layers of glacial till or hardpan close to the surface.
• Sloped lots where gravity flow is impractical.
• Environmentally sensitive areas requiring uniform, highly treated dispersal.

How soil type affects septic choice

The results of your soil log will point you directly to the right system type.

• Clay Soil: Has slow percolation rates. It almost always requires an engineered system like a mound, an Aerobic Treatment Unit (ATU), or an OSCAR.
• Sandy Loam: Considered perfect for a conventional gravity system.
• Gravelly Soils: Can percolate too quickly, risking groundwater contamination. These sites often need an engineered system to ensure proper treatment before dispersal.

In Snohomish County, discovering inadequate soil conditions during an inspection is a common trigger for a mandated upgrade to an engineered system.

Real-World Repair Scenarios

Understanding when a replacement becomes necessary can be clarified with real-world examples.

When repairing isn’t feasible—case examples

A simple repair is often off the table for properties with significant issues, such as:

• Drain fields that are completely saturated and consistently fail percolation tests.
• Pipes that have been crushed or broken by encroaching tree roots.
• Evidence of illegal or unpermitted modifications made by previous owners.

Case Example: A homeowner on a 0.4-acre lot in Snohomish failed their routine inspection. Their conventional gravity system was too close to a property line, and the soil was a dense glacial till. Repair was impossible. Davis Septic Design was brought in to design an OSCAR system that could fit within the tight setbacks and function properly in the challenging soil.

Who qualifies for an OSCAR upgrade?

To upgrade to an OSCAR system, you must meet certain criteria:

• A recent soil log and site evaluation must be completed by a licensed designer.
• Your existing system must be officially designated as failing or inadequate.
• Your property likely has constraints like a small lot size or a high water table.
• The design must be approved by the Snohomish Health District.

Davis Septic Design provides comprehensive feasibility studies to evaluate your property and determine if an OSCAR system is the best and most compliant solution for you.

How long does installation take?

A typical project timeline for a replacement system is:

• Soil Log & Design: 1–2 weeks
• Permit Approval: 2–4 weeks (can vary based on the health department’s workload)
• Installation: Approximately 1 week

Complex sites with steep slopes or difficult access may take longer. We recommend starting the soil testing process in the spring or summer to ensure faster processing and better weather for installation.

Maintenance and Longevity

The long-term health of your system depends on understanding its unique maintenance needs.

Routine upkeep differences

OSCAR System:

• Requires periodic maintenance of the pump station and controls.
• May need occasional flushing of the drip lines to ensure they are clear.
• Regular monitoring of the sand media integrity is part of the inspection.

Conventional System:

• Simpler upkeep, primarily involving tank pumping and occasional line checks.
• No pumps or complex moving parts to service.

For Both Systems: Plan to pump your septic tank every 3-5 years and never overload the system with grease, “flushable” wipes, or harsh chemicals.

When to call for service

Be proactive and call for a professional consultation if you notice any warning signs:

• Pooling water or foul odors near the tank or drain field.
• Alarms sounding from the control panel (specific to OSCAR and other engineered systems).
• Sewage backups in your home’s drains.

The team at Davis Septic Design offers consultations to help you diagnose issues early, potentially saving you from a more costly emergency repair.

Final Advice

Making the right decision requires a clear assessment of your situation.

Decision checklist for homeowners

Ask yourself these questions to determine the best path forward:

• ✅ Do I have limited space or challenging soil conditions?
• ✅ Has my system officially failed an inspection?
• ✅ Is my priority a long-lasting system that meets all current codes?
• ✅ Is my property near wetlands or other environmentally sensitive areas?
• ✅ Am I prepared to invest in a reliable, engineered solution for long-term peace of mind?

If you answered “yes” to several of these, an OSCAR system is likely the right choice for your property.