Gravity System

As the name implies, gravity drainfields work by letting gravity drain the effluent from the septic tank into a series of underground trenches. This means the drainfield area must be below the elevation of the septic tank. If this is not the case, then a pump is necessary and it is called a pump to standard gravity system.

When you send new liquid waste into the septic tank, an equal amount of liquid (called effluent) comes out the outlet side of the tank. An “outlet filter” is installed in the tank to help prevent solids from escaping the tank.

After passing through the outlet filter, the effluent flows through a distribution box (d-box) which diverts the flows to multiple pipes.

The effluent leaves the d-box under the power of gravity and flows downhill to each of the underground drainage trenches. The trenches are made up of perforated pipe over drainrock  Each type effectively does the same thing…they allow the effluent to “perc” into the ground at the bottom of the trench.



Services We Provide

Service Area

  • Battle Ground, WA
  • Brush Prairie, WA
  • Camas, WA
  • Hazel Dell, WA
  • Hockinson, WA
  • La Center, WA
  • Meadow Glade, WA
  • Mill Plain, WA
  • Ridgefield, WA
  • Vancouver, WA
  • Washougal, WA
  • Woodland, WA
  • Yacolt, WA