20 Feet can be a huge difference if a water vein is near your house it will fill, his tile maybe draining or seeping elsewhere. I live in the sump pump capital of the world so let me know if you need any other advice.

the real trick is to make sure you have a back up sump pump because the ALWAYS fail sometimes months sometimes years,,,,like the Oil Pressure guage on a W124, it just a matter of time.