We provide you with the best possible septic options and designs. Call us for perc testing and a soil evaluation before you purchase property to see what a new septic system will cost.

Qualified Team

We only hire the best in the business, so you can be sure you’re working with the best designers, builders and inspectors. It is not just the quality of the design, but the quality of the entire experience.

Forward Design

We create unique designs specifically for you. We promise to look at the details of how your system will be used and offer our best and most cost-effective recommendations to you.

Superior Support

We’re here for you – before, during and after. We are not set in our ways and we are happy to adapt to the needs of our clients under the county and state regulations.


For over 50 years the McNair family has been designing septic systems in Washington State. In 1972, Scott McNair began working for the Clark County Health Department. He left that position a few years later to begin his own on-site septic design company. Scott continued designing systems for the next 30 years.

In 2005, Scott’s son, Cory began working with him. Cory graduated from Northern Arizona University. After several years managing a restaurant, then a bank he was ready for a change. Working with family was a great privilege and one that was not taken for granted. They were able to enjoy several great years working together before Scott lost his battle with cancer.

In 2015, Andrew Winslow joined the team. Andrew graduated from Whitworth University. In 2019, he was licensed by the state of Washington as an OSS Designer. He is continuing to learn about this evolving industry and develop the knowledge to effectively analyze every aspect of the septic design, installation, and maintenance processes.

In February of 2021, our team grew with the addition of Alan Salazar. Alan graduated from California Polytechnic University Pomona with a BS in Civil Engineering and in 2014 completed his EIT certification. Amid the unique challenges of 2020, Alan, and his wife (2019 newlyweds) made the decision to transition north to be closer to family in the greater Vancouver area. Alan brings 5+ years of construction management, civil engineering, and plumbing design experience to the team and looks forward to growing his skill set and experience in the septic design industry.

Having two licensed designers on staff to review each project has further allowed McNair Septic Design to uniquely design creative and cost-effective designs throughout Southwest Washington. We believe that they are the only company in Southwest Washington with two licensed designers on staff. So no matter which one of them you speak with, you will be working with a professional.

Septic Design Experts Since 1975
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I just love my new septic system! I really couldn’t have picked a better company to work with. McNair Septic truly is the best!

We hired them to redesign the septic system for our office building. We’re so happy with the results they’re doing our other 5 locations as well!

We just broke ground on my new custom home and hired McNair to install our septic system.  The team has kept me very involved in the process – I can’t wait to see the finished project!