Welding Plastic, especially polyethylene  depends a lot on how the plastic
was damaged.  If the sun got to it, forget it.  If the molding process left
some thin spots, good luck.  If there's plenty of soft pliable material
there, I'd drill a 3/16" hole in each end of the crack for stress relief and
try my luck.   However, the P-tex may not get the cracked material to the
proper temperature for a good bond.  it works great on skis however, but
your not fixing cracked snow skis.  It will also depend on whether you have
cross linked polyethylene or linear.  Linear is much easier to weld.

Seelye and Draeder make excellent  plastic welders.  The Draeder is a hand
held heat gun looking unit with a $2400 price tag on it.  I've got a
portable Seelye complete with compressor and extra heat element and a couple
of tips(about $1100 worth of stuff) that has about 5 hours on it I'd be
willing to sell or trade stuff for.  it all fits in a 24" wide tool box and
weighs about 30#.  The ribbon and rod welding rods go with it.  Have poly
and ABS.  I bought the thing to weld cracked canoes and kayaks and there is
little market for that.  Would also sell it for cash; quite a bit of it!

There's a urethane based resin that has limited success in repairing
polyethylene, but it's real expensive and there's no guarantee it will
permanently solve the problem.

Dimwitted Moose and Flying Squirrel.  90GL   148k and no 3rd gear.
-----Original Message-----
From: Dar Crammond <DCrammond@AOL.COM>
To: vanagon@GERRY.VANAGON.COM <vanagon@GERRY.VANAGON.COM>
Date: Monday, May 29, 2000 9:26 PM
Subject: Fixing polyethylene

>Hello list:
>I have recently found out that my gray water tank on my Adventurewagen has
a
>leak.
>The tank is cracked where the dump outlet connects the tank.  Originally,
>this looks like the two were molded together in one piece and not welded
>together later.
>Though the tank is painted black, a cross sectional view of the damaged
area
>looks an awful lot like polyethylene.  It feels like it too.
>My limited experience with this material is that general purpose plastic
glue
>does not really work on it.  I might consider welding it with a p-tex stick
>from my ski tuning drawer, but that seems kind of shaky, too.
>Anyone out there with experience with repairing / welding polyethylene?
>DAR