Fall Septic Prep: What Thurston County Homeowners Should Do Before the Rainy Season Returns
September in Western Washington is a transition month. The dry, busy days of summer are winding down, and the long, wet winter is just around the corner. For homeowners with septic systems in Thurston, Pierce, and Mason Counties, this brief window of mild weather is the most important time of the year for property maintenance.
When the heavy rains return in late fall, the soil on your property will become saturated. A septic system relies on relatively dry soil to filter and treat wastewater. If your system is already struggling, or if your property does not drain properly, the winter rains can trigger a messy and expensive failure.
Taking a few proactive steps in September can protect your system, save you money, and give you peace of mind all winter long. Here is your fall septic preparation checklist.
1. Schedule an inspection and pumping
The most important step you can take in the fall is to have your system evaluated. The average household septic system should be inspected at least every three years by a septic service professional.1 If you cannot remember the last time your tank was checked, do not wait until December.
Household septic tanks are typically pumped every three to five years.1 Your tank should be pumped if the bottom of the scum layer is within six inches of the bottom of the outlet, or if the top of the sludge layer is within 12 inches of the outlet.1
Pumping the tank in the fall provides maximum capacity for the winter. If a system is full of sludge when the heavy rains hit, the excess water can stir up the solids and push them into the drain field. Once solids clog the drain field pipes, the system will fail, and a new drain field will have to be installed at a different location.2
2. Check your property drainage
Water runoff from roofs and drainage ditches can saturate the soil.2 Drain fields are most efficient when the soil beneath them is not saturated.2
In September, take a walk around your property and look at how water will flow when the rains return. Are your gutters clean? Do your roof downspouts discharge water away from the drain field?
Keep roof drains, sump pumps, and other rainwater drainage systems away from your drain field area.1 Excess water slows down or stops the wastewater treatment process.1 If you notice that your yard naturally slopes toward the drain field, you may need a professional excavation contractor to grade the area or install a French drain to divert the surface water safely away from the septic components.
3. Protect the drain field from winter traffic
Most drain fields are constructed in open lawn areas and are not designed to handle vehicles or heavy equipment driving on them.1 The weight of vehicles and heavy equipment compacts the soil, which can damage pipes.1
During the summer, you might have parked an RV, a boat, or a utility trailer on the grass. As fall approaches, make sure none of these are parked over the drain field or the designated replacement (reserve) area.2
Furthermore, if you are planning to have winter firewood delivered, ensure the delivery truck does not drive across the drain field to dump the load. Create a physical barrier if the area is accessible to cars, livestock, or heavy equipment.2
4. Locate and clear your system components
When a septic emergency happens in the middle of a January rainstorm, the last thing you want to do is dig through the mud trying to find your septic tank lid.
Use the dry days of September to locate your system. Know where your drain field and replacement area are located.2 If you do not know where they are, you can contact the Thurston County Building Development Center to request a copy of the record drawing (as-built) for your system.2
If your tank does not have risers (extensions that bring the tank access lids up to ground level), consider having them installed this fall. Risers make future inspections and pumping much easier, with little to no digging required.3 Thurston County even offers a small rebate program for the installation of septic tank risers on existing systems.3
| Fall Prep Step | Why It Matters Before Winter |
|---|---|
| Pump the tank | Removes sludge to prevent solids from washing into the drain field during heavy rain.1 |
| Divert roof drains | Prevents roof runoff from saturating the drain field soil.1 |
| Move heavy vehicles | Prevents soil compaction and crushed pipes in the drain field area.1 |
| Locate the tank | Ensures quick access for emergency pumping during winter storms.2 |
| Install risers | Eliminates the need to dig through frozen or muddy ground for maintenance.3 |
5. Address slow drains now
If you have noticed that your sinks are draining a little slower than usual, or if your toilets occasionally gurgle, do not ignore these warning signs. A sluggish system in September will likely become a backed-up system in November.
A failing system can cost a lot of money in repairs and hurt the health of your family, pets, and neighbors.2 If your system stops working and sewage backs up into the home, it can cause additional property damage.2 Having a professional diagnose the issue while the ground is still dry makes repairs faster, easier, and less destructive to your landscaping.
Trust the local experts
Preparing your septic system for winter is not just about pumping the tank; it is about ensuring your entire property is ready to handle the rain. Because South Bay Septic and Excavation LLC handles both septic services and site grading, we can address the whole picture—from pumping your tank to grading your yard to keep stormwater away from your drain field.
If you live in Thurston, Mason, Pierce, or Lewis County, do not wait for the winter storms to test your septic system. Contact South Bay Septic and Excavation LLC at 360-233-2783 today to schedule your fall inspection, pumping, or drainage consultation.
