My sump pit has three drain tile runs discharging into the sump  pump pit.  There is one 3 inch tile installed about 19-1/2 inches (bottom of the tile) below the floor slab and two 4 inch tiles at about 11-1/2 inches (bottom of the tile) below the floor slab.  My present pump water level setting is in the middle of the 3 inch tile (18 inches below the slab).  My pump only operates for about 25 seconds (turn on to turn off).   I'd like to dramatically increase this pump operational time.  It has been suggested that I can raise the water level set point by 7 to 10 inches.  In the reading I've done, I have been unsuccessful at finding a recommendation for a maximum water level in the sump pit before the pump turns on.  Do you have any recommendations?  Should I have any structural concerns about the house (footings, wall, water intrusion) if I increase the maximum water level?