The Septic Rule Starts November 1. If You Are Selling This Autumn, It Already Applies to You.

If your place is on a septic system and you are thinking about selling, this one is worth ten minutes of your time.

The Snohomish County Board of Health has adopted an ordinance requiring every septic system to be inspected before a property is sold. It takes effect November 1, 2026. The Health Department announced it back in April and said it would spend the summer and fall doing outreach to realtors, contractors and homeowners. That outreach has not reached my office yet, which is most of the reason I am writing this now.

Why this matters in September

November 1 sounds far away. It is not, because the date that counts is the day you close, not the day you list.

Take a listing in the first week of October and you are almost certainly closing in November. Nobody sells a house in three weeks by accident. So a seller who lists this month or next is already inside the new rule without having done anything wrong.

The good news is that the timing works in your favour if you move early. An inspection can be done up to a year before closing. Get it now and it covers you straight through next summer.

What the rule actually requires

Straight from the Health Department's announcement:

• A certified septic professional has to inspect the system
• The tank must be pumped if the inspection calls for it
• The inspection can be completed up to one year before closing
• It applies to every property sale in the county that has a septic system

This is not Snohomish County inventing something. The ordinance brings the county into line with a new state law making these inspections mandatory everywhere in Washington. King, Skagit and Island counties have required them for a while already. We are catching up, not leading.

How many of us this hits

The Health Department counts roughly 84,000 private septic systems in Snohomish County, and about 2,800 septic properties changing hands every year.

If you picture that as a rural problem, look again. Plenty of those systems sit in unincorporated ground north and east of Arlington, which is where I spend most of my time, but the department specifically calls out Lynnwood and Mukilteo as well. A 1970s neighbourhood inside city limits can be on septic and most of the people living there never think about it.

If you are selling

Do this in whatever order suits you, but do the first one this month.

Book the inspection now, not at listing

A failed inspection found in September is a repair you schedule. The same failure found in escrow is a renegotiation, and you will be having it from the weaker position with a buyer who has already started packing.

Find out what you actually have

The Health Department keeps an online database of septic records by property. It will tell you what type of system is on your ground and what the file says about it. Ten minutes, no cost.

Look at the rebates before you spend

The county's Savvy Septic program offers rebates, grants and guidance to homeowners keeping their systems working. If your system needs help, check that first rather than after you have paid for it.

If you are buying

You are the one this was written to protect. The Board of Health's stated reason was to keep buyers from inheriting an expensive problem they could not see, and that is a fair description of a septic system: buried, out of sight, and capable of costing more than a kitchen.

What changes for you is that the information now arrives as a matter of course rather than because you thought to ask for it. Read the report properly. A system can pass an inspection and still be near the end of its service life, and those are two different sentences.

What I am not going to tell you

What it costs. I have seen numbers quoted for septic work in this county that range from a few thousand for a tank swap to well past thirty for a full replacement on difficult ground, and the honest answer is that it depends entirely on your soil, your site and what is already in it. Anyone who gives you a figure over the phone without seeing the property is guessing.

Get a certified inspector out and get a real number. That is the only version worth acting on.

The part I would actually worry about

Not the rule. The queue.

There are 2,800 septic sales a year in this county and a finite number of certified inspectors in it. Everyone who lists between now and spring needs one. I do not know what the wait will look like in late October and neither does anyone else, but I know which direction it goes when a deadline lands on a fixed supply of people with the right certification.

Booking in September costs the same as booking in October. It just happens sooner.

The bottom line

From November 1 a septic inspection is part of selling a home in Snohomish County. The Health Department's own line on it is that if you plan ahead, the requirement will not slow your sale down. I think that is true, and I think the planning ahead is the whole of it.

If you are on a septic and you are thinking about selling in the next year, book the inspection now. It is good for a year, it costs you nothing extra to do it early, and it turns a possible surprise into a piece of paper you already have.

Sourced from the Snohomish County Health Department's media release of April 17, 2026. For questions about your own system or the requirement, the department's septic pages are here. This is general information about a rule change, not legal advice.