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Question of the Week: Can a pump be installed in a two compartment IM-Series septic tank when a sealed pump chamber is not required?

Posted on by Ashley Donnelly

Each week our technical services team fields hundreds of calls into our tech line. We’ve been getting this question quite often: Can a pump be installed in a two compartment IM-Series septic tank when a sealed pump chamber is not required?

First, you must confirm with the local regulatory code to make sure this tank configuration is allowed by code. If so, this guidance is intended for a single tank application in which a pump or pump vault is installed within a two compartment Infiltrator IM-Series Septic Tank (septic tank and pump tank within the same tank). The baffle wall is not sealed and cannot be sealed. As is the case with any single tank system that incorporates a pump it is good practice to have smaller pump doses. A smaller pump dose volume will minimize the pulling of solids through to the second compartment.

For example:  A 1 to 2” drawdown in liquid level is recommended. Set Aquaworx Control Panel or float system accordingly.

  • IM-1060 a 1” drawdown equals a 25-gallon pump dose. A 2” drawdown equals a 50-gallon pump dose.
  • IM-1530 a 1” drawdown equals a 35-gallon pump dose. A 2” drawdown equals a 71-gallon pump dose.

Please check the local regulatory code as it may require a minimum dose volume. Filling the pipe volume itself can be significant depending on the length of the main and number of laterals. If the pressure dosing design for the drainfield requires a larger volume dose, then it may be better to incorporate a separate pump chamber such as the IM-540 tank. The IM-540 tank has a working capacity of 475 gallons is optimal for in-series applications, retrofit applications to increase the volume of an existing septic tank and is Ideally sized for use as a trash-tank or pump tank. 

View IM-540 Cut Sheet

Please see Table 2 of the IM-Series Septic Tank Installation Instructions for IM-Tank Nominal Volume chart.  

Example Drawings:



For more information on installing a pump in an Infiltrator IM-Series septic tank please contact our Technical Services Team.

About the Author: 
Ashley Donnelly
Inside Sales and Technical Services

Ashley Donnelly is the Infiltrator Water Technologies Inside Sales representative for the Western United States and Canada. Ashley entered the onsite wastewater industry over 18 years ago and is committed to the industry and public health. She has a passion for preserving the environment through sound wastewater treatment solutions. In her position at Infiltrator Ashley is responsible for assisting engineers, contractors and regulators with technical and design information, training, installation, and operation & maintenance of their onsite wastewater needs. Ashley is a member of the Arizona Onsite Wastewater Recycling Association (AzOWRA) and National Onsite Wastewater Recycling Association (NOWRA). She attended Central Connecticut State University majoring in Communications. Ashley resides in Connecticut with her husband and their three children. In her free time, she enjoys spending time with family, the outdoors, and volunteering.