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  • Sump pump model and switch adjustment

    Background:

    I recently bought a house with a 1600 sqft basement (floor is 7 feet below the ground level). Two weeks ago there was a lot of rain and the basement had 4" of standing water within a few hours. It turned out that the old sump pump (a Simer 1/2 HP, 1900 gph @10 ft) stopped working. The water receded within 24 hours, but the sump pit was still almost full.

    Today I installed a Zoeller M98 pump in the pit. This pump is sitting on a layer of bricks at the bottom of the pit. It rained yesterday, so the pit was almost overflowing today before I installed the pump.

    When I turned the pump on the first time, it took 45s for the pump to lower the water level in the pit and then turn off. After that, there was an alternate cycle of the pump turning on, and off (water was rushing into the pit from the drain pipes while the pump was off). At first, the pump on time was about 10s and the off time was 12s. About an hour later this went down to an on time of 8s and an off time of 20s.

    The diagram below shows the water level in the pit when the pump turns on. It also shows the pit dimensions (18" diameter and 22" deep), the drain pipe heights from the bottom of the pit (9" and 10"), and the water levels at which the pump turns on and off (11" and 6"). I believe the drain pipe on the right (9" above the pit base) has a much longer run than the other drain pipe.


    As you can see in the diagram, the pump does not turn on until there is about 11" of water in the pit. Since the drain pipes are 9" and 10" above the pit base, the pump does not turn on until there is some standing water in the drain pipes.

    Questions:

    1. Do I need to adjust the pump float switch so that the pump turns on before the water level in the pit reaches the drain pipes? This way, the drain pipes won't have 1-2" of standing water in them before the pump turns on. In a slow season, it may take a few days for this much water to seep in the drain pipes. This means that the drain tiles below the basement floor could be quite wet before the sump pump even turns on. If I should reduce the turn on height, how would I do this? Options I can think of are to put a spacer at the top of the float slide bar, and also to replace the bricks at the bottom with something of a lower height.

    2. Would the Zoeller M53 be a better fit than the M98? I am concerned that the M98 pump may be too powerful and so cycling too much. The water discharge is about 10 feet above the pump outlet. Since the M53 would take longer to empty out the pit, the incoming water from the drains may just keep that pump from turning off at all. The M98 is 1/2hp and pumps 3600 gph at 10 feet. The M53 is 1/3 hp and can pump 1900 gph at 10 feet. I do plan to finish the basement soon, and so don't want to have a situation where there is heavy rainfall, and the sump pump is not powerful enough to keep up with the heavy rain. Of course I don't want to see the pump cycling too much and burning up either.
    Last edited by pitter; 12-13-2010, 12:13 PM. Reason: updated image

  • #2
    Re: Sump pump model and switch adjustment

    I don't know what kind of switch you have, but a corded float switch would be the best. Then you can tether it to the vertical pipe with more cord than normally comes with the pump. This will stretch out the on and off times which will make the motor last longer. Just make sure the float can't come to rest on top of the pump or anything else which would keep it running indefinitely.

    Another thing I would consider is a battery backup system in the event of a power outage once the basement is finished.
    Frequently asked questions about pumps and tanks.

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    • #3
      Re: Sump pump model and switch adjustment

      Originally posted by speedbump View Post
      I don't know what kind of switch you have, but a corded float switch would be the best. Then you can tether it to the vertical pipe with more cord than normally comes with the pump. This will stretch out the on and off times which will make the motor last longer. Just make sure the float can't come to rest on top of the pump or anything else which would keep it running indefinitely.

      Another thing I would consider is a battery backup system in the event of a power outage once the basement is finished.
      I have the version of the sump pump that comes with a vertical float switch.

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      • #4
        Re: Sump pump model and switch adjustment

        In my experience, those switches can't be adjusted very much if any. Some pumps give you the option of using different switches. In your case, you would have to disable your vertical switch by either getting inside the pump and doing some wiring changes or locking it on the on position then using a piggy back float switch to operate the pump.
        Frequently asked questions about pumps and tanks.

        Comment


        • #5
          Re: Sump pump model and switch adjustment

          Originally posted by speedbump View Post
          In my experience, those switches can't be adjusted very much if any. Some pumps give you the option of using different switches. In your case, you would have to disable your vertical switch by either getting inside the pump and doing some wiring changes or locking it on the on position then using a piggy back float switch to operate the pump.
          I believe this picture shows the M53 and M98 in comparison. The M53 appears to turn on at a lower level of water. I was thinking of putting in a 1" tall pvc pipe ring around the float shaft at the top of the float of the M98. This would give the float less travel distance on the float shaft and so turn on the pump at a lower water level.



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          • #6
            Re: Sump pump model and switch adjustment

            Actually they are identical. The float arm is the same length, so the travel up and down is going to be the same. This is the kind of switch that you can adjust.
            Attached Files
            Frequently asked questions about pumps and tanks.

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            • #7
              Re: Sump pump model and switch adjustment

              I found one method of turning on the float switch sooner. I wrapped a little duct-tape around the float rod, just above the float. The tape keeps the float from moving up the float rod as the water level gets higher and therefore the switch lever begins moving up sooner and therefore turns on the switch sooner.
              Normally, as the water level gets higher, the float travels up the rod but doesn’t cause the switch lever, attached to the rod, to move up and turn on the switch UNTIL the float touches the switch lever.

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              • #8
                Re: Sump pump model and switch adjustment

                Wonder what your insurance will say about that

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