I think it likely that a piece of wood has mostly plugged the pipe, then caught a bunch of leaves and sticks to complete the plugging. The pressure washer is a good idea, or you could dry assemble joints of PVC pipe and push them in as you assemble them. That won't do a lot of good, though, if the plug is at the ell. Try ramming something in from the top. If you cannot unstop it, an external siphon could be installed to drop the pond level.
I think if the pipe was collapsed it would still be flowing some.
Last edited by John F; 03/26/17 09:18 AM.
