What is the purpose of the observation pipes being installed at an elevation to view the horizontal or level infiltrative surface within the dispersal cell?

• A. They are installed at an elevation to view the horizontal or level infiltrative surface within the dispersal cell.
• B. They are installed only for decorative purposes.
• C. They are installed to vent the septic tank.
• D. They are installed on the exterior of the cell.

Answer: (A)

Observation pipes are placed in the dispersal cell at elevations that line up with the infiltrative surface so you can see the level of the horizontal absorption area. The height of the water column in these tubes acts as a direct readout of how far the effluent is elevating the infiltrative surface and how evenly it’s spreading across the bed. By checking that level, you can confirm the infiltrative surface is at the design elevation and that the bed is being wetted uniformly. If the surface sits high in the tube, it can indicate overloading or buildup (like a biomat) restricting infiltration; if it’s too low, the system may be underperforming or not receiving enough effluent. This visual gauge helps ensure proper distribution, prevent surface ponding, and support ongoing system performance. They’re not for decoration, venting, or exterior placement.