Brett Stomps | Windermere

The Dirty Details of Septic Inspections

Table of Contents
Table of Contents

Dirty Details

Recently, it’s becoming obvious that the forms (mainly in Washington) regarding septic inspections are “gray”. If your agent doesn’t know how a septic system works, by the time you’re under contract, it may be too late. Let me expand:

Like all of the content that I produce, I aim to bring transparency to buyers and sellers in the Columbia Gorge. Frankly, most of the agents who conduct business out here are not as professional as you think they are. I write about this topic because it’s their lack of knowledge (or general practice) that are hurting the very consumer they profit from – you.

If you are buying or selling a property in Washington with a septic system, then this article is important to you.

What is an OSS?

Let’s start off with the basics, keeping in mind that this is not an article on septic engineering.

The term, “OSS” is referred to on the Washington forms and it stands for, “Onsite Septic System”. A standard gravity fed septic system includes a:

  • Septic Tank (size is based on the number of bedrooms or frequency of use)
  • Diversion Box (also called distribution box or d-box)
  • Drain field lines (also known as soil absorption system or leech lines).

Advanced septic systems (such as nitrate reducing systems) have a lot more going on, and we are not getting into that here.

Here’s an image of a standard gravity fed septic system:

If you were buying a house on a septic system, what would you expect to be inspected by a professional?

The Septic Addendum is Not Clear Enough

This is where everything turns to you-know-what (💩).

You see, “Seller shall have the OSS inspected and, if inspector determines necessary, pumped by an OSS service company at seller’s expense”. This is the exact language from the Washington septic addendum (Rev. 3/21). This is the seller’s default obligation.

If seller has pumped and inspected the tank in the last 12 months, then (usually) the seller does not have to have the system inspected again.

No problem right? Wrong.

What about the lines from the house to the septic tank? From the tank to the d-box? Or from the d-box to each individual drain field line?

The Inspection is Only As Thorough as Who The Seller Hires

If an agent does not know how a septic system is built, and they do not specifically ask the seller for more than this in an offer, then you (as a buyer) only get what the septic company (that seller hired) determines as an inspection. You may not get an inspection of the sewer line from the house to the tank, the tank to the d-box, and from the d-box to the drain field lines.

So how will you ever know if the drain lines are crushed or filled with roots? In this instance you won’t.

You and your agent have to specifically request what inspections you want because if seller hires Bishop Sanitation for example, Bishop’s base inspection only includes a septic tank pump and a visual inspection of the system. It does not include scoping.

If your agent forgets this in your offer and later you realize you aren’t getting this inspected, will need to convince the seller during your transaction to allow you to do invasive inspections after your offer has already been accepted. That’s a bad time to ask for a favor.

Most septic inspectors in the Columbia Gorge conduct a standard septic inspection like Bishops, which is not all inclusive and is not always accurate.

Standard Septic Inspections Are Not Enough

In Oregon, the septic addendum outlines the different parts of septic inspections that the buyer can ask for in their offer, which sets the expectation for buyer and seller for inspections. Whereas in Washington, the seller’s obligation is to hire a professional to inspect the system, but it does not define how.

The argument is, with companies like Bishop’s Sanitation, their base service to test the drain field by flowing water into the tank. If water does not percolate, the drain field has failed, or, if water percolates out, the drain field is operating. They may also walk around on top of the drain field and see if the ground is mushy, or smells funny.

To companies like Bishop Sanitation, this test is enough for them to determine if the drain field is operation.

To be accurate, your agent must expressly state on your septic addendum what you want to be inspected, and how.

To me, I highly recommend having cameras stuck down the septic lines. From the house to the tank, from the tank to the d-box, and from the d-box to each drain field line.

Listen to this Success Story

I was working a transaction with some buyers up in Snowden. Knowing my 💩, I requested that the entire septic system be scoped head to toe, in addition to the default pumping and inspection of the septic tank.

The seller hired Bishop Sanitation, a company well regarded for being quick and therefore popular with real estate agents. Bishops came a day early, unannounced to buyer or seller (whom buyer had the contractual right and desire to attend the inspection).

I happened to be there for a well inspection with M&K Pump & Drill (who has very in-depth inspections by the way). I greeted Bishops and they began their inspections.

Bishops offers the basic level of septic inspections that can be offered. They begin flowing water into the septic tank and they tell me that the drain field was accepting the water, and therefor in great condition. What I knew that they didn’t, was that the tank was 41 years old, and that 2 of the 4 drain field lines had been replaced 20 years ago. The other 2 were 41 years old.

It was obvious to see by the designs submitted to the health department (that I pulled for the transaction) that the drain field was going right through a stand of trees. This usually means trouble. So, Bishops marks on their report that the drain field was operational based on their version of a flow test. There were also some notes that the tank was cracked. The tank was marked as “fair condition”, and the drain field was marked as “good condition”.

Bishops left, and the next day, Roto Rooter came out on time to inspect the lines (per the language in the septic addendum that I added). It was revealed that all 4 septic drain field lines were crushed, broken, and full of roots.

For my clients, I challenged the report Bishop’s gave with the photo evidence of the lines and we had an entire new septic system replaced by seller prior to closing. Why Bishops trusts this style of flow test is beyond me. I saved my clients $15,000 and a lot of headache.

Get Your 💩 Together

So, in closing yet another real estate article for here in the Columbia Gorge, the status quo remains the same for buyers and sellers. Interview your real estate agent. For agents, keep practicing, keep training, and keep applying pressure to our local third party professionals to do better.

Bishop’s is just an example, but I have to ask the question, why are they just now offering scoping services when so many companies out there already were? Maybe I stirred the pot just enough.

The Columbia Gorge is an expensive place to live, and professional services reflect that, and when we’re spending top dollar, it’s wise you know what you’re getting for your money.

Thanks for tuning in.


The information provided on is intended to be educational and accurate. However, information on does not substitute as buyer and seller due diligence when transacting real estate. Buyers and sellers are advised to work directly with a licensed real estate professional, seek additional professional services when applicable, and to inquire at the state, county, and city offices for their due diligence.