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.

Be very careful.  If you live in a area with highly expansive clays, turning off your sump and allowing the water to overflow would result in disaster.  Expansive clays have enough force to lift a 10 storey structure with increased moisture contents and under the right conditions. 

If your sump quits working, the result will be

- your basement floor will heave, usually in the middle or where there is increased moisture.
- your footings may experience diferential movement with changes in moisture conditions.  This generally rotates your basement walls outward, cracking your walls, making it is so your windows and doors won't close properly and many other problems and you will have to continually adjust your teleposts in your basement.

I agree with your initial post (8 gallons/minute is excessive - unless it is raining or there is lots of melting snow or you are watering your lawn or a significant meteorological event is occurring).

GeoPaveTraffic is absolutely correct.  Make sure you have excellent positive drainage all the way around your house and that your eaves extend well away from your house as well and that your neighbors eaves aren't directed at your house.

If you have excellent +ve drainage, the lawn isn't being watered and there is not big moisture influxes caused by meteorlogical events then there may be some other problems that can be investigated.

- There is a possiblity that yours or the city's water or sewer lines may have sprung a leak.  Check with your neighbors.  Are they having the same issues or is it just your house.  Is there water bubbling up from the ground somewhere in your street or back alley?  Is your water meter continually running even if you aren't using water (if you have a water meter).

- Is your house on a hill side where a spring may be present?  Again check with your neighbors and investigate that ground in your neighborhood.  Is there water bubbling out of the ground nearby or is there a spot that is always soft and never seems to dry up?

I advise against adjusting your float on your pump.  This may just allow water to flow back into your weeping tile, changing the moisture content of the soil around your footings and presto, you've got heaving problems at the base of your footings.  It sounds like your sump is performing the way sumps are supposed to.  Ten gold stars to the contactor!  If you can't nail down the source of your water influx, get in touch with a reputable geotechnical engineer and get their help.

MORE NEWS