How to connect pipes to a septic tank

Once you've placed and levelled the septic tank, it's time to install septic tank pipes. Septic tank manufacturers cast inlet and outlet holes into the tank. Many manufacturers make a watertight connection by sealing a rubber boot to the concrete. High water infiltration rates cause septic systems to eventually fail. Installing watertight pipe connections increases a septic system's longevity.

Locate the 10 cm (4 inch) sewer stub installed at the home.

Clean the 10 cm (4 inch) sewer stub and clean-out assembly hub with polyvinyl chloride, or PVC, primer. Clean-outs are required and enable future line maintenance.

Coat both the sewer stub and clean-out assembly hub with PVC cement and press together. Twist the clean-out assembly a quarter turn until it is level, and then hold it for 30 seconds.

Insert the clean-out assembly onto the stub until you've fully inserted the hub. Twist the pipe a quarter turn to evenly spread the adhesive.

Dig a trench with the excavator's bucket from the tank's inlet elevation to the house's plumbing stub. Maintain a 2-percent slope from the house to the tank.

Lay the 10 cm (4 inch) schedule 40 pipe into the trench with the pipe markings pointing up until you've filled the entire length of the trench.

Clean both ends of each pipe with PVC primer.

Coat the pipe end and pipe hub with PVC cement and press them together. Twist their connections a quarter turn and hold them together for 30 seconds. Repeat this process for all of the pipe connections in the trench.

Insert the pipe into the inlet opening of the tank until the pipe sticks in about 5 cm (2 inches). Locate the pipe far enough into the tank that incoming waste water does not follow the tank wall down but free-falls out of the pipe. The pipe must be at least 15 cm (6 inches) from the baffle to prevent clogs from forming.

Heat the tar sealant in direct sunlight for 15 minutes.

Clean the void between the newly installed pipe and the septic tank concrete with a wire brush to remove any debris.

Fill the void between the pipe and the concrete with the tar sealant. Press the sealant into the void with a trowel. If the septic tank has a rubber gasket moulded into the tank for the pipe, tighten down on the securing clamp.

Back-fill the newly installed pipes with a hand shovel taking care not to disturb them.


When applying tar sealant, be sure to allow the concrete to fully dry before applying for better adhesion. When backfilling around the septic tank pipes, take care not to disturb the new pipe-to-tank seal.

Things You'll Need

  • Excavator
  • Level
  • Shovel
  • Tar sealant
  • Trowel
  • Clean-out assembly
  • 10 cm (4 inch) Schedule 40 PVC pipe
  • PVC primer
  • PVC cement
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About the Author

Stephen Hasty started writing in 2009. Covering technical articles and newsletters, his work has appeared in "The Kennebec Valley Plumbing Newsletter" and "Maine Leasing." Hasty holds a bachelor's degree from Saint Cloud State University, a real estate sales agent license and a master plumber license from the state of Maine.