I think I remember reading an article that Mike Otto did for Pond Boss Magazine saying that over "X" inch dia of pipe, you needed equipment to push it together and hold it until the glue set up. I don't remember the size tho.....

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).