We moved in to our new home 20 months ago. We have a sump pump in our basement in an 18” x 24” polyethylene pit.  The water level rises about 8” and the pump runs for 6-8 seconds just about every hour. My calculations indicate the water is flowing in at about 8 gallons an hour. This seems excessive to me.
I also noticed that no water ever comes in through the 4” inch inlet pipe.
In an attempt to find the problem I turned the pump off and manually drained the pit. Keeping the pump off I then let the pit fill up naturally to see if it would overflow. Fortunately it did not overflow. The water level rose to about 16” and stopped just below the inlet pipe.
I manually drained the tank again, and saw that water appeared to be coming in from the very bottom or floor of the pit under the raised pump.
I assume that water should only enter the pit through the inlet pipe. If this correct, this leads me to believe there must be a crack or hole in the bottom of the pit.
•    Can the pit be patched or must it be replaced?
•    And would this solve the influx of water or is it likely to seek a new level?
•    Is it likely that the pit was defective at installation
•    Given that it was not, is hydrostatic pressure a likely suspect and would it just crack a new pit?

The water should generally enter through the inlet pipe, however, there is nothing wrong with it entering through the bottom of the pit.  I have seen manufactured pits that do not have a bottom.

As for sealing/patching the bottom of the pit, I would recommend against it.  The fact that the bottom is open may be preventing water from getting to the pipe, i.e. the bottom of the pit is acting as a drain and keeping the water level lower.

If you turned the pump off for a long time, it is likely that the water would overflow the pit.  A question, did you leave the pump off until the water level was stable for several days or just until the rate of rise decreased or appeared to stop?  It may have been the the water was comming in and flowing into the pipes and that caused it to appear to stop rising since the volume required to raise an inch increased dramatically.

I would recommend that you look around the outside of the house as this is where many, but not all, water problems start.  Make sure that all of your downspouts are in pipes leading away from the house and that nothing drains toward the house.

The water should generally enter through the inlet pipe, however, there is nothing wrong with it entering through the bottom of the pit.  I have seen manufactured pits that do not have a bottom.

As for sealing/patching the bottom of the pit, I would recommend against it.  The fact that the bottom is open may be preventing water from getting to the pipe, i.e. the bottom of the pit is acting as a drain and keeping the water level lower.

If you turned the pump off for a long time, it is likely that the water would overflow the pit.  A question, did you leave the pump off until the water level was stable for several days or just until the rate of rise decreased or appeared to stop?  It may have been the the water was comming in and flowing into the pipes and that caused it to appear to stop rising since the volume required to raise an inch increased dramatically.

I would recommend that you look around the outside of the house as this is where many, but not all, water problems start.  Make sure that all of your downspouts are in pipes leading away from the house and that nothing drains toward the house.

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