I have two sheer descent waterfalls. Both operate from the same pump. There's is a T-junction that controls flow to each waterfall. One of the waterfalls is no longer spewing water. Even if I set the flow to the highest level and only to this waterfall, the water just trickles down against the wall very slightly. I don't know where to even begin troubleshooting. My local pool shop offered to dig up the pipe next to it and try to blow out any possible blockage. I've read some forum posts that this could be caused by blockage within the unit itself. I would like to avoid any extra repair costs. Replacing the unit will be complicated and will require removal of the stone coping above the waterfall. Has anyone had experience with this issue?