Have a submersible sump with a siphon backup in a 2 foot deep lined pit. Here's the problem. Usually the pit is bone dry - When we get 1.5 - 2 inches of rain the pump starts cycling as one would expect. With this amount of rain however, the pit will fill past the point of the submersible's capacity and the back up kicks on. Both pumpls are now pumping. If heavy rain persists, I have to put in a utitlity pump or the water will overfill the pit and flood the floor.
Here's where it gets tricky. After several hours of all three pumps pumping at full force, and with the water level at the top of the pit, past the trip point for the submersible and the siphon, I've unplugged the submersible and turned off the backup siphon pump (to see if they're needed after such a long time of continuous pumping). The water level, after turning them off, remains at the top of the pit - without spilling over onto the floor. Why is this so? Is the water level around my house at this level and the pumps are simply pumping out water only to have it replaced as it goes out. (Forgot to mention I do have a check valve in place.) I know that I need the pumps because I have had flooding down there. Do I need a deeper pit? Was the drain system around the house improperly installed? Do I need a higher capacity pump? I bought the highest output pump a reputable store had and it was professionally installed by a licensed plumber. As I mentioned, I have the backup and also put in the utility pump, as needed.
I have asked everyone I think could help and no one knows how to help me.
Anyone have an idea? What is happening here?

 

What kind of pumps do you have? Its a gallons per minute thing. And yes a deeper pit will help. How deep is your pit 2 ft? Take pics. Three pumps????

Mike NJ

 

I doubt the coincidence of the water table being at the same height as the pit. I would visually confirm the output flow of each pump by running the hoses onto the yard. You could also run your a pump into a basement drain temporarily to eliminate the theory that all you're doing is recirculating ground water.

 

I've done both. The utility pump I drop in is discharged into the stationary sink and I have also used hoses to discharge out to the street. What stumps me is when I turn all the pumps off and the water just sits there at the top of the pit. Why isn't it overflowing?

 

You're quite likely correct that the water table is higher than the top of your sump. You can pump forever and that won't change until the water perks into the ground and the level gets below your slab.

A 2' deep sump seems a little shallow. Both of mine are deeper and fairly large diameter. A larger sump will reduce the cycle time.

I run two pumps and when we have really wet periods in the spring the "water table" is higher than my basement floor. The pumps run almost continuosly for days. I live on the top of a hill, but unfortunately below the topsoil the ground is heavy clay. It takes a long time for the water to perk through the clay.

Of course it all depends on your definition of water table. The true water table is the level where the ground is permanently saturated. However, when the ground gets saturated during heavy rain a temporary water table can form very near the surface.

 

Can I just dig the hole another foot deeper to see if that rectifies the situation without doing any damage? What's the best way to proceed. The liner in the pit has a plastic bottom. I suppose I just break through that with a spade, dig another foot or so, put some gravel on the bottom and reinstall the pumps. I'm not familiar with exactly how to adjust the float on the submersible pump to allow for the extra foot or so of water I want in the pit before the float trips the pump on. Any ideas? More importantly, does this help solve the overall problem?