Most homes outside city sewer in Blackfoot, Shelley, and the rest of Bingham County treat wastewater on the lot. Understanding the tank and field is how you know when to call for pumping versus an inspection — and when a soft spot means a bigger job.
Septic system components
Most residential systems have three main parts: the tank, the soil absorption system (drainfield), and the plumbing that connects them. The tank collects wastewater and separates solids from liquids; the drainfield disperses treated liquid into the ground so soil can finish the job.
How wastewater moves and is treated
Wastewater from the house flows into the tank where heavy solids settle and lighter materials (scum) float. Naturally occurring bacteria break down some solids. Clarified liquid exits past the outlet baffle to the drainfield, where the soil filters and treats it before it reaches groundwater. Idaho’s Technical Guidance Manual and Southeastern Idaho Public Health (SIPH) rules set the minimums for tank size, setbacks, and vertical separation from groundwater — not a national “rule of thumb.”
What Idaho requires on a house system
A dwelling tank starts at 1,000 gallons, with another 250 gallons for each bedroom over four. The outlet baffle has to keep solids in the tank. If it is missing or backwards, sludge rides into the drainfield and a routine pump-out becomes a replacement.
The lot also has to keep a full replacement drainfield. That empty area is how you still have a legal repair when the first field clogs. Around Blackfoot, irrigation-season groundwater, canals, and shallow basalt are often what pushes a lot from a standard trench to an alternative system. See local conditions and our design and installation page. Pump timing for the tank you already have is on the pump calculator.
Why regular pumping matters
Over time solids accumulate. If the tank isn’t pumped, solids can exit to the drainfield, clog the soil, and cause costly failure. Regular measurement and scheduled pump-outs — typically every 3–5 years for Blackfoot households — keep the system functioning for decades.
Common parts we check during service
- Baffles and tees — keep solids in the tank and protect the outlet
- Tank integrity — cracks or corrosion allow leaks and root intrusion
- Scum and sludge depths — guides pumping frequency
- Distribution box and field — check for even distribution and signs of surfacing
Homeowner tips
- Avoid flushing grease, wipes, and non-biodegradable items.
- Don’t drive or park heavy equipment over the drainfield.
- Know where your tank lids are and keep them accessible.
- Schedule regular inspections and pump-outs (typically every 3–5 years).
Related guides
Read signs your septic is failing and what to do during a septic backup. Ready for the truck? Call (208) 980-7333.