How to bond/seal polyethylene?

SeaNile

SeaNile

Well-Known Member
Aug 16, 2010
1,522
Chadds Ford, PA
Boat Info
2003 50 Sundancer
Engines
Cummins QSM11
I have an ever so slight leak from my fresh water tank which is made from polyethylene. What can I use to cover this small leak? I can't access the tank from the bottom so the repair will be made from inside the tank.

I know from experience and now google that the usual 4200, 5200, LifeCaulk, etc., will not work. I'm kind of at a loss here. It's not even like a fiberglass patch would work.

Any suggestions??
 
This works excellent on plastic auto fuel tanks which I believe are the same. It states on the package that it works on plastic water tanks also. The most important thing is to make damn sure it is fresh as it dose have a semi short shelf life.
https://www.autozone.com/sealants-g...oxy/p/j-b-weld-tankweld-repair-kit/698473_0_0

PS They are drilling holes in plastic fuel tanks now to steal the gas which most cars have all had for quite some time.
 
So close! JB Weld rep respond to another review stating: “will work on most plastics, save for polyethylene and polypropylene”.
 
The tanks on the boat lifts popular in our area are molded polyethylene. My boat lift dealer uses a soldering iron. He just melts some additional plastic into the crack. It works on small cracks or holes.
 
techmitch said:
This works excellent on plastic auto fuel tanks which I believe are the same. It states on the package that it works on plastic water tanks also. The most important thing is to make damn sure it is fresh as it dose have a semi short shelf life.
https://www.autozone.com/sealants-g...oxy/p/j-b-weld-tankweld-repair-kit/698473_0_0

PS They are drilling holes in plastic fuel tanks now to steal the gas which most cars have all had for quite some time.
Click to expand...
Is that really the correct link? The package says its for "anything made of metal".

Been there, done that. On a personal level I have tried to fix a few tanks over the years. The product advertisements all tout "best", but in every case I ended up replacing the tank. Nothing worked long term.

Then, we had an industrial tank get damaged at my plant. Since it was worth many thousands, the Plant Manager wanted it fixed, not replaced. I searched local companies, including the manufacturer of the tank, and they said no problem. I spent hundreds for a guaranteed industrial repair. It lasted only weeks. My guarantee required them to replace the tank.

It also depends on the size and cost and thickness of the tank. Tanks can be "welded" with the right equipment and knowledge, but it weakens / thins the spot. That usually requires removing the tank to work on it.
 
SeaNile said:
I have an ever so slight leak from my fresh water tank which is made from polyethylene. What can I use to cover this small leak? I can't access the tank from the bottom so the repair will be made from inside the tank.

I know from experience and now google that the usual 4200, 5200, LifeCaulk, etc., will not work. I'm kind of at a loss here. It's not even like a fiberglass patch would work.

Any suggestions??
Click to expand...

You can try this if you can actually get to where it is cracked: https://www.harborfreight.com/plast...ahiStwDLOO35_UgvQsNnBh4BzW-AKG4waAhIvEALw_wcB

I haven't had any luck with Polyethylene. It seems once it cracks it's gone.
 
techmitch said:
This works excellent on plastic auto fuel tanks which I believe are the same. It states on the package that it works on plastic water tanks also. The most important thing is to make damn sure it is fresh as it dose have a semi short shelf life.
https://www.autozone.com/sealants-g...oxy/p/j-b-weld-tankweld-repair-kit/698473_0_0

PS They are drilling holes in plastic fuel tanks now to steal the gas which most cars have all had for quite some time.
Click to expand...

Do you think this would work for mending a polyethylene plastic seat shell back together? I am having my upholstery done and the double helm seat is cracked where the top and bottom meet. I am also on Frog Mortar Crek, come on spring!!!
 
Todd1465 said:
Do you think this would work for mending a polyethylene plastic seat shell back together? I am having my upholstery done and the double helm seat is cracked where the top and bottom meet. I am also on Frog Mortar Crek, come on spring!!!
Click to expand...
This stuff won't work for something like that, but if you post some good pics of the piece I'm sure the collective CSR minds would have some suggestion's for the repair.

Actually, you should probably start a new thread. I'm sure we can help.
 
techmitch said:
This stuff won't work for something like that, but if you post some good pics of the piece I'm sure the collective CSR minds would have some suggestion's for the repair.

Actually, you should probably start a new thread. I'm sure we can help.
Click to expand...

Great idea. Is there a button to click to start a new thread? I have never done it before, I just read everyone's threads.
 
SKybolt said:
The issue is pretty much nothing sticks to Polyethylene for any length of time.
Click to expand...
That's what I always thought and know 2 guys that had to go the tank removal and plastic weld route and they were very successful for 4-7 years they owned them after the repairs were done.
Me, if I'm pulling a tank, it's getting replaced even if it has to be custom made.
 
 
techmitch said:
That's what I always thought and know 2 guys that had to go the tank removal and plastic weld route and they were very successful for 4-7 years they owned them after the repairs were done.
Me, if I'm pulling a tank, it's getting replaced even if it has to be custom made.
Click to expand...

Yeah I totally agree. Best if it is replaced. I did that when I first got my boat, had new custom aluminum tanks made.

I like aluminum over the poly because it withstands possible punctures better.
 
SKybolt said:
Yeah I totally agree. Best if it is replaced. I did that when I first got my boat, had new custom aluminum tanks made.

I like aluminum over the poly because it withstands possible punctures better.
Click to expand...
"punctures" I can surely appreciate the forward thinking, but the mere thought of such gives me the creeps.
 
Thanks for all the help. I'm going to do the repair with West System G/flex 655 plastic boat repair kit. Doesn't specifically call out Polyethylene but does mention HDPE which is very similar aside from density and a few other physical properties.

80 grit sand paper, acetone, propane torch and a little West System and I should be good to go.

I've come this far with taking everything apart I am going to see if I can just pick up the tank and turn it upside down.
 
The "PE" in HDPE stands for polyethylene.

Have used a plastic soldering iron and melted in some stainless mesh as a reinforcement, before. That was about 7 or 8 years ago and it was around a corner, too - typically the hardest place to seal well.
 
SKybolt said:
You can try this if you can actually get to where it is cracked: https://www.harborfreight.com/plastic-welding-kit-with-air-motor-and-temperature-adjustment-96712.html?ccdenc=eyJjb2RlIjoiOTE1OTA3MjMiLCJza3UiOiI5NjcxMiIsImlzIjoiNzEuOTkxIn0=&utm_source=google&utm_medium=cpc&utm_campaign=19749941456&campaignid=19749941456&utm_content=147345898540&adsetid=147345898540&product=96712&store=3025&gclid=Cj0KCQiA0oagBhDHARIsAI-Bbgf_4KqLblli7B5VdRznuKLahiStwDLOO35_UgvQsNnBh4BzW-AKG4waAhIvEALw_wcB
Click to expand...
I use this same gun at work to build acid tanks out of HDPE. Get some welding rod and a chunk of plastic to go along with it for practicing. It's not rocket surgery, but it does require a bit of finesse. Think "oxy-acetylene", but not anywhere near the temps!
 
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