Septic System Anatomy
Inlet/Outlet Tee
An inlet tee and an outlet tee are T-shaped pipe fittings installed at the points where wastewater enters and exits the septic tank. The inlet tee directs incoming sewage flow downward into the tank body, preventing turbulence that would disturb the settled sludge layer and prematurely mix the tank contents. The outlet tee (sometimes called the outlet baffle or sanitary tee) extends downward below the floating scum layer to draw only the clear middle layer of effluent toward the drainfield — preventing grease and floating solids from escaping the tank.
Older systems used concrete baffles that performed the same function as tees; these often deteriorate over time. Modern systems use plastic tees that are more durable. Missing or broken outlet tees are a common cause of premature drainfield failure, as solids bypass the normal separation process and flow directly into the drainfield soil.
What This Means for You
Ask your service technician to check both the inlet and outlet tees during every pumping visit. Replacement is inexpensive and straightforward when caught early. A missing outlet tee that goes unnoticed for years can cause drainfield failure that costs tens of thousands of dollars to fix.
Related Terms
Septic Tank · Baffle · Effluent · Scum Layer