A few days ago I asked about repairing a leaking polyethylene water tank,
then did some research on my own.  Well, I tried (because it was available
locally at my sailboard shop) some  stuff called "Water-weld" that I found
while looking for the supposed real stuff, and the WaterWeld failed
miserably!  After painfully disassembling my camper and pouring water all
over as I wrestled that  water tank out through the door, I  followed the
directions then  reconnected the tank and put some water in...Worked ok
until it was almost full, then the patch let go, dumping about 20 gallons of
water inside...Ugg.
  So I went back to find some "Mr. Sticky's Poly-Bonder" which is said to be
the one product that will structurally bond Polyethylene.  I ordered some
from the below, and while there on the website found lots of cool stuff that
might help out some of you "project types"  I ordered at about 9am and got a
tracking number for the shipment by noon..so they seem to be on top of it
here.

http://www.tapplastics.com/

  Don Hanson