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How to size an sewage ejector pit?

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I have two floor drains going to an ejector pit, the drains are in a ballroom area where the drains will hardly be used


asked Mar 4, 2020 by Maurice Walden

1 Answer

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Each floor drain with 2" trap counts 3 FU (fixture units). If the trap size is 3" then it would be 4 FU.

based on the trap size, add FUs for number of traps (you have only 2). Each 2 FU would be 1 gpm.

The total of FU converting to gpm would be the pump flow.

The head of the pump would be the amount of static (vertical run) plus the pressure loss in vertical and horizontal run.

As there is no a sump pump with low flow like 2 gpm, thus need to select the smallest pump and create a space in the pit at the point below the height of the pump to store the water until 2 to 3 times of the pump's nominal flow then discharge the stored water.

For more information check the link below:


answered Mar 6, 2020 by Matt Hall
edited Mar 9, 2020 by Matt Hall

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