First, I want to thank everyone here for their help - it really gave me a jump
start on fixing my water tank.
Here's what I found:
- The tank is definitely made of LDPE (low density polyethelene). HDPE does
NOT stick to it, so don't even begin to think that all polyethelene is the
same. You can weld LDPE to HDPE, but not HDPE to LDPE.
- Welding is the preferred method for fixing by comparison to epoxies
designed to fix polyethelene.
- I used a hot air blower welder from Harbor Freight Tools - it cost about
$50. In hindsight, I probably could have done a better job with one of their
soldering iron type that heats a hot disk end. Getting smooth melting of the
rod into the tank plastic is very important, and I kept having issues with the
plastic from the rods bubbling. In the end, I took a torch, heated up an old
putty knife, and using that to smooth the edges. I'm sure this is partly
because I don't get along particularly well with welding and soldering. It's
the one task I have to teach myself to do better. Ideally, I think I would
have used the type of welder that feeds strips/rods through the tip of the
welder, but that one was not immediately available.
- You want to weld the plastic with strips, not rods. Strips are easier to
work with. If you can't find LDPE strips online, keep looking around the house
for #4 recycleable plastic. The only place I found it around our house was the
snap-on tops to Tupperware type containers. If you are buying strips, buy more
than you think you'll need. I bought 5' of strips, and I could easily have
used 10 to lay on the thickness I wanted.
- Practice welding HDPE, say with a cracked old paint bucket or something.
HDPE is much easier to find around the house, as laundry detergent bottles, and
just about every other piece of recyclable plastic (except clear bottles) is
made from it. Once you learn how to weld with HDPE, the process with LDPE is
the same, and it will go much more smoothly.
- Clean the tank with MEK. I did it both before and after the
- Using a dremel, grind out a groove (this is actually pretty important, so
don't skip this step). Even if you go through the tank, don't worry, you can
build it up again with the strips.
- Find a YouTube video or two to watch the process.
- Sand the area with 80 grit sandpaper.
- Drill a small hole at the ends of the cracks to keep the cracks from
- At the suggestion of another poster, I layed in a layer of stainless mesh
over the crack thinking that if it cracked once, it might do so again, so
reinforcing the area would be a good idea. Time will tell.
- Be sure to water test it before putting it back in the boat.
Hoping this set of step-by-step instruction helps, Bruce Whitmore1994 C&C 37/40+
(847) 404-5092 (mobile)
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