Posted: Thu Feb 10, 2011 9:15 pm Re: Rena XP3 - noise?
I had a similar problem with an XP1. On youtube I came across the suggestion that this can be the result of the filter not being far enough below the tank. The manufacturer apparently specifies that 24" below the tank is the minimum for proper functioning of the filter. sure enough, when I lowered mine to almost 24" below the tank, the problem went away, though it did take about an hour.