Fluid problem

Hi, i am learning fluid animation, all is going really well except for some weird thing:

i did water falling into a glass and some of it splashes out, my problem is that when i check frame by frame, suddenly from frame 32 to frame 33 a big amount of water “spawns from nowhere” replacing the drops that where on the floor.

youtube example:


any solution?

another thing: i had to put the lower limit of the domain at the same position with the plane, because the itself didnt collide with the water even i enabled fluid => obstacle for the plane and for the glass. planes cant be obstacles?

please help me!