When I first got my skimmer I followed the instructions and had the outflow pipe under the water about 5". It created too much back pressure and I learned it should be above the water line. I cut it off above the water line and the skimmer worked great, but it sounded like a waterfall in my sump.
Tonight after work I took another piece of pipe a little longer so it was just under the water and drilled holes in it to relieve any pressure. It is really quiet and seems to be working as well as when it was cut shorter. Here is a shot.
Is there any harm in this?