I have a newly impounded and filled 16 acre lake with a 54" diameter riser pipe spillway. I would like to raise the height about 6" to put the water up on my dock without getting high enough to kill an oak on the bank. The pipe is corrugated and I have already raised it 18 inches due to contractor error in setting it. I used a pipe coupler and a rubber gasket but this was expensive. The pipe has a 36" antivortex baffle bolted to 4 legs on top which gives me a sturdy support. If the design fails and I lose the 6 inches of water, no big deal. Any ideas?