We never had good luck fusing tanks. Had issues splitting at weld without adding filler rod. Problem went away with filler rod.

Can also adjust heat by concentrating tip more on filler rod than on material if needed. Quicker than modulating pedal.

www.hoosierpondpros.com

[Linked Image from lh6.ggpht.com]
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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).