Site Drainage & Sump Pump Questions

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    • #279150
      Avatar photoBruce A Somers

        I’m a landscape contractor. A client I have just moved into a building they bought. In the parking lot there is a drain at the bottom of a recessed loading dock. This drain has a 4.5″ pipe leading to a catch basin that is roughly 425 cubic feet. The catch basin has a 12 HP sump pump at the bottom that pumps into a 2″ pipe that leads out to another smaller storm water catch basin, and hopefully from there it runs to the street storm water basin. The sump pump wasn’t working, so the catch basin didn’t empty so the loading dock didn’t empty for a couple of days after a 1″ rain. I have some questions that maybe some of you can help me with.
        1. We believe that sump pump is not big enough to move that much water in a timely matter? What would you suggest?
        2. Is the 2″ pipe the correct size to handle that much water? That may be predicated by the pump requirements? It seems that all of the pipes leading to the drain are 4″ and 4.5″ but there is only a 2″ pipe to remove it.
        3. The drain at the bottom of the loading dock is 2′ by 2′ by 2′ deep with a 4.5″ pipe at the TOP of the basin. So there is about a foot or so of standing water at the bottom of the basin that doesn’t go away until it eveporates apparently. In the mean time, it seems like a perfect mosquito breeding ground & the water sitting in there sure doesn’t smell good. Shouldn’t this be set up with the pipe set low in the drain basin to avoid the standing water issue?
        4. The basin with the sump pump is extremely moist which seems to corrode the electrical out let & the pumps plugs. Is it OK to hard wire the sump pump so that it can be completely sealed from moisture?

        Thanks for any help.


      • #300136
        Avatar photoRetired plbg1

          If the pump has a 2″ openning in it then thats all the water you will get out. The pipe in the sump is up high so the dirt dont run down the drin. Why do you have pump in there, it is suppse to hold the water till it reachs the pipe.The sump has to be cleaned out, because the dirt will clog up pump and burn it out.I guse you can hard wire it as long as you have it on a breaker, check with pump co.

        • #300137
          Avatar photoBRL

            Thank you. The pump is in a separate basin from the drain that I wrote about in question #3. Basically the water first goes through that drain, then through the 4.5″ pipe over to the large basin that the pump is in. Then the pump is used to empty that basin into the drain system that we believe ties into the storm water system in the street. It seems that the recessed loading dock is probably lower than the drain system, so it would never be able to drain to it. So this system was set up to drain the loading dock area out to the storm drain system.

            So back to question #3. If I am maintaining this property & I keep dirt from building up in the loading dock area, which would then keep it out of that drain; I should be OK installing a shallower drain that would allow for any little bit of dirt that may get washed in to be trapped, but yet give that basin a chance to evaporate so that it is not filled with stagnant water all of the time. Does this sound correct?

          • #300138
            Avatar photoKen Zoeller

              ?#1. use the biggest pump you can fit in the 2’x2’x2′ pit. Use a pump with 2″ sphere size through it. a 2″ ejector.
              ?#2. 2″ pipe out is OK because the 4″ in is by gravity and out will be under pressure by the pump.
              ?3#. The pump “OFF” pouint should dictate the leave in the pit.
              ?#4. The pump should be hard wire in a water tight junction box. This will require a “disconnecting means” with in sight of the pump. This is just like your AC unit outside. It has a “disconnecting means” so it can be worked on safely.
              Go to and look at sewage pumps model M282(100 GPM@10′) and M292(125GPM @10′). These are the biggest 115V unit we make. If you have 230v available M284(135GPM @10’or M294(180 GPM@10′) we make a M295 (195@10′). I would use M294 if 230V are available. The reason to use a solids handling unit is to handle the leaves and stuff that will come to the pump.

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