I had a Flood in my basement and used a portable sump pump and hose to pump out the water for several days. The basin is about 2 feet deep with some gravel at the bottom.

Once i finally got the water out to the level of the gravel, I shut off the portable sump pump and installed a new sump pump with check valve.

After a few days, the basing keeps slowly filling up to about 6-8 inches. The float trigger for the new sump pump is about 10 inches from the bottom.

With so many dry days, why does the basin keep filling up with water? Do Sump Pump basins always have a certain level of water in them? Is this normal?


1 Answer 1


The level of water in a sump pump basin is dependent on the water table of the surrounding terrain. That level will vary with rainfall, conditions of drought, localized flooding, melting snow, etc.

One must adjust the float to keep the water intake submerged, which prevents the pump from running dry when the conditions allow for an empty basin. That is to say, if the intake opening is two inches deep, your float should not trigger the pump until the water level is higher by a reasonable margin.

For your two foot deep basin, ten inches is a safe margin. It prevents the pump from operating so frequently as to cause premature failure, but also provides for basin depth for days in which the water ingress is heavy.

  • That makes sense. But for almost 2 years, with all the raining, i never seen the water level above the gravel before, until the original sump pump died. Is it common to go a few years with the basin always water free and then in a low rain year, the basin is about 6-8 inches full of water?
    – isaacco
    Feb 12 at 3:13
  • The answer to that question may have to come from a hydrologist, as it will be based on ground conditions and local weather/precipitation. Stretching this answer a bit, it could also be based on nearby construction, but that falls into the ground conditions aspect. Vibration from equipment can affect adjacent properties, but that's a long reach.
    – fred_dot_u
    Feb 12 at 9:36
  • This also depends on the design of the pump, of course. Many will leave a small amount of water when they stop.
    – keshlam
    Feb 12 at 15:24

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