Mine runs on the side. I don't think it would make a difference in straight down or running it on the side. I think what makes the big difference is how high is the pipe from the water. The lower you have the pipe the less noise, and the higher the pipe the more you will hear splashing. I have mine I want to say about 2 inches above the water I can't really hear any splashing, but also I have the stand doors closed. Hope this helps...