Septic Tank
The septic tank is the primary underground holding vessel for all wastewater leaving a home or building. It separates solid waste from liquid effluent through settling and natural bacterial action, holding solids while allowing clarified liquid to flow toward the drain field. It is the first and most fundamental component of any on-site sewage system.
What It Does
1Separation of solids, grease, and liquid
When wastewater enters the tank, three layers form naturally. Heavy solids (sludge) settle to the bottom, where bacteria slowly digest them. Fats, oils, and grease rise to form a floating scum layer at the top. The middle layer - clarified liquid effluent - is what flows forward to the drain field. The baffles at the inlet and outlet direct flow through the middle layer, keeping solids and scum contained.
2Bacterial digestion of organic solids
Anaerobic bacteria in the tank break down organic material in the sludge layer over time. This process reduces - but does not eliminate - the accumulation of solids. The remaining sludge and scum that bacteria cannot fully process must be removed by pumping. Without regular pump-outs, solids build up until they overflow toward the drain field.
3Holding capacity and pump-out interval
Tank size is measured in gallons. How quickly a tank fills depends on household size, water use, garbage disposal use, records, and what enters the system. Ask General Septic and applicable health authority how those factors should inform a pumping request.
Observable Signs That May Involve This Component
These signs may help describe a service need - they do not constitute a remote diagnosis. General Septic can assess the system on site as part of the requested service.
All fixtures draining slowly at the same time
When every drain in the house runs slowly - not just one fixture - the issue may be in the tank or further downstream, not in an individual drain line. A full tank, clogged effluent filter, or blocked outlet baffle are possible causes.
Sewage odor inside the home
A functioning septic tank vents gases through the home's plumbing vent stack. If odors enter the living space, it can indicate a full tank, a dried-out P-trap, a damaged inlet baffle, or a vent obstruction. Persistent indoor sewage odor can be described to a plumber or General Septic.
Wet or unusually green grass near the tank location
If the area directly over the buried tank appears wetter than surrounding ground, or if grass is noticeably greener in a defined area, the tank may be leaking or surfacing. This should be evaluated before it worsens.
Gurgling sounds from plumbing fixtures
Gurgling in drains or toilets - especially after flushing - can indicate that the tank is approaching capacity or that the outlet is partially restricted. It often appears before a full backup develops.
What Information Helps When Requesting Service
Having this information ready gives General Septic useful context when planning the requested service:
- When the tank was last pumped (year is sufficient if you are unsure of the month)
- Number of people currently using the system
- Whether any fixtures are currently backing up or draining slowly
- Whether a garbage disposal is used regularly
- Any recent large water uses - events, guests, laundry catch-up
When to Describe a Request
Describe a request if you have not had the tank pumped in several years, if multiple drains are running slowly, if you detect sewage odors indoors, or if the area over the tank appears wet or saturated. Before a real estate transaction, confirm the applicable inspection and filing requirements with the county. Do not continue normal water use during a backup; share the symptoms with General Septic.
Related Services
Describe a request in the greater Seattle area
General Septic directly provides septic services across King, Pierce, and Snohomish counties with its staff and equipment. Describe what you are observing so the team can plan the work.