I need both groundwater drainage as well as laundry room sewage pump in basement.

Should they be separate pumps (asump pit with pump and 40 liter sewage ejector reservoir with pump) or could ground water drainage be connected directly to ejector pump reservoir?

If so, any precautions need to be made to avoid sewage water going under the floor in drainage pipes? Or does that add too many risks and best to go with two separate systems?

  • 3
    In many areas, attaching sump pumps to the sanitary sewer is illegal, since it adds groundwater/stormwater to the sewage treatment plant load and contributes to causing untreated releases during storm events when the plant capacity is exceeded. In areas where the storm and sanitary sewers are the same single sewer it may be legal.
    – Ecnerwal
    Commented Jun 24, 2020 at 11:56
  • 1
    @Ecnerwal Sounds like an answer... Commented Jun 24, 2020 at 12:33
  • 1
    Even if you have a septic system rather than town sewer, overloading it with "clean" water is a bad idea. I don't know of any USA locale where it's legal to empty a sump pump into municipal storm drains, either. Typically they have to empty into local drywell or just onto the ground. Commented Jun 24, 2020 at 16:33
  • Is this only gray water not sewage (gray water is washer and sink drains no toilet). If it is just gray water I would go with the cheaper sump pump to drain the pit , next where is the system draining now?
    – Ed Beal
    Commented Jun 24, 2020 at 19:17
  • Sewage is draining to private/local treatment setup. I don't expect much groundwater though, as ground is mostly clay
    – lietus
    Commented Jun 25, 2020 at 13:43

1 Answer 1


At the end I will go with 2 pumps and 2 reservoirs. Sump pit and small pump will be deeper, but only for emergencies as I don't expect much water there. For ejector pump I'll go with all-in-one pump that will be placed in sealed reservoir under floor. Better redundancy and avoiding accidental mix of sewage and drainage this way.

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