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Sump Pump Size - too big?

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  • #16
    the purpose of a larger pit is to allow for a longer cycle time. since floats work on height of water, a pit that is larger in width is better than a deeper pit. the pump should be lower than the inlet of the pipe when the pump turns on. this way the inlet will not be constantly full of water sitting in the pipe.
    the pedistall pump has a float rod that allows for a larger cycle curve. you can adjust the limit stops to allow for on at top of pit and off above pump impellers. a typical sump pump with a built in float doesn't have an adjustable range. it typically turns on between 9-11'' and off at approx. 4''. this is why the width of the pit is more important than the height. you need a larger volume of water to allow for a longer cycle time. the pedistall will compensate for a deeper pit.

    you mentioned that the pit is 20'' x 20''. that should be large enough. water volume is 7.48 gallons per cubic foot. as plumber mentioned you want to make sure that the check valve is working properly and that water doesn't return into the pit when the pump shuts off. a 10' head is very small. a smaller h.p. pump can handle the head with no problem. you need to determine how much water per hour needs to be pumped when a heavy rain occurs. a second pump is very nice, especially if damage would occure if the pump fails. a water powered pump might not be a good idea in a basement. if your discharge line plugs, the pump will actually flood the basement. the pump will continue to run, using fresh water to move out the pit water. the fresh water will be approx. 6gpm. these pumps are better suited for outdoor areas and areas where power is a problem.


    rick.

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    • #17
      Increasing the size of your sump and installing a pedestal pump is more about preventing your pump from cycling then anything else. With a pedestal pump your pump sits above the sump and your float has the entire height of the riser to use for float adjustments. With your current pump the float adjustment is very limited.

      As stated earlier you first need to determine what your source of water is. If you have water year round it is likely ground water. Now you need to figure out how much water you are trying to pump. Again using a bucket to see how quickly you evacuate the sump with your pump is the easiest way to do that. Again sizing your pump is only important to assure you have a pump which is up to the job but will not cycle.

      I’m unclear what you meant by leaving water in the pipe but make sure you have a check valve installed in your riser so the water in the riser does not re-enter the sump on pump shut down. If your demand is really low you may also want to consider putting your pump on a timer.

      As for finding out whether your line is leaking that is a little harder. For the most part you would have to dig it up unless you have a way to fill the line with water to test it. You may also want to watch the water level as your pumping and if the water seems to fill the sump faster during pumping that could be an indication of a leaking discharge line. If your discharge line is not too deep you could also try to use a tile probe in the area of the discharge line to see if the ground is wet around the discharge line.

      Mark
      "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

      I never lost a cent on the jobs I didn't get!

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      • #18
        Rick,

        Sorry I guess we were typing at the same time.

        Mark
        "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

        I never lost a cent on the jobs I didn't get!

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        • #19
          I'm with Rick. I think you need a larger pit. It seems obvious that your pump is oversized for the volume contained in the pit, if it is in fact evacuating it that fast. If the pump is shutting off before the float has dropped, your switch, or float is bad.

          The problem with replacing your pump with a smaller one is that you may find it is undersized during rain conditions.

          the dog
          the dog

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          • #20
            SO if I stay with a 1/2 HP pump (move to a zoeller) and it cycles often after a rainstorm... that's ok? Also... when I said "pipe" I was refering to the drainage pipe that sits under the concrete floor and drains water into my pit. I'm curious where the "on" point for the pump should be. I can adjust this higher by placing bricks under the pump if need be, but I want to know if water in those pipes is ok or not.

            I notice that when there is no rain... water is coming into the pit from around the sides of the lower portion of the pit (if you can imaging... the pit looks like it is made up of two parts... the wall and the "bucket" that sits within it. ) the water seems to "stop" coming in when it reaches a certain level (I'm assuming this is because the force coming in and the "weight" equalizes") This means that there is always water in the pit... and the level it equalizes varies but is usually 1/2" below to 1 1/2" above the bottom of the black pipes coming into the pit)

            I have no hole drilled into the 1 1/2" discharge line, but so far as I know the check valve is fine.

            I do notice that the sump pump itself seems to shoot water out of the side of it (I see this when the water level gets below that point when pumping, but it could be doing that the whole time)... is this normal?

            How are the switches with the zoeller pumps? I want to be sure that with frequent cycling after a rain event that the switch will ladt me for a while.

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            • #21
              Peccotrice,

              1) It is not alright for the pump to be continously cycling on and off at any time. The important point is that you do not want to size the pump based on your regular dewater needs, only to find that is is undersized during the rainy season. You need to size the pump based on your heaviest water demands. At that point the size of the pit should be sized so that the water volume does not exceed the pump discharge, and allows for enough containment volume to allow the pump to run relativly steady.

              Does the pump cycle on and off even during heavy rains? If so, the pump is probably over-sized. If not, then you need a larger pit.

              2) I'm not necessarily in agreement with Plumber on using a pedestal pump. I'm not dead against it either, I don't see alot of advantage to it. I do agree that you need an adjustable float switch. I can't speak for a Craftsman, but many submersible pumps are available or can be converted of an adjustable system.

              3) So in summery:

              You need to determine how your pump functions during rain. If it cotiniously evacuates the pit, replace it with a smaller one. If it runs fine, you need a bigger pit, and an adjustable float switch. This will allow more water to be contained before the pump begins to discharge. The pump will then (if sized correctly) discharge enough water to keep the pit from over flowing, yet run continiosly.


              the dog

              [ 10-11-2005, 03:00 PM: Message edited by: plumbdog10 ]
              the dog

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              • #22
                Re: Sump Pump Size - too big?

                Originally posted by plumbdog10 View Post
                Peccotrice,
                3) So in summery:

                You need to determine how your pump functions during rain. If it continuously evacuates the pit, replace it with a smaller one. If it runs fine, you need a bigger pit, and an adjustable float switch. This will allow more water to be contained before the pump begins to discharge. The pump will then (if sized correctly) discharge enough water to keep the pit from over flowing, yet run continuously.


                the dog

                [ 10-11-2005, 03:00 PM: Message edited by: plumbdog10 ]
                Confused here: "If sized correctly, it will run continuously." OR "If it continuously evacuates the pit, replace it with a smaller one." It seems like you are saying two different things. Does "running continuously" mean something different than "continuously evacuates the pit"? If not, which statement is wrong?

                I too live on a river. My record of my pump not running is 3 days. After the Noreaster, my pump cycles on and off every minute. Been thinking of a pedestal pump to raise my float trigger as the water level seems to slow down a lot just as it approaches the foundation pipe.
                Last edited by davidscubadiver; 04-17-2007, 09:22 AM.

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