Fixing Plastic Freshwater Tank

[gonesail]

west marine says the new flexible epoxy will stick to plastic.

[MarkJ]

Originally Posted by steamgoat

Why not cut a hole in the tank where the crack is and fit a round plastic tank access panel,the type they fit to clean out tanks ??

Because its in a bit thats curved.

Originally Posted by Vasco

One thing good about the tanks in a 393, they're quite easy to remove. It might be worth your while to get a replacement, Mark.

Yes, and its the forward tank which can be whipped out pretty easy. But, being a cheapskate, I'll try a repair first.

I have a few days to think about it..... i.e. I need to drink a lot of water first

Then I am thinking... OK don't laugh:
1) Buying a small butane burner that they use in kitchens to do Creme Brulee and welding a bit of milk bottle container(etc) to the crack.

2) Cyanoacrylate and Sodium Bicarbonate. Put Bi Carb of Soda in the crack and pour Superglue on it. Heats the plastic and burns the putty in.

3) Boiling Beer for my coffee for the rest of my life.


The Tap Poly Weld as shown in that video looks good, but I doubt I can buy it here in Grenada.

But there are threat thoughts from everyone on a problem that I thought would be an easy fix.

Nothing is an easy fix on a boat!





Mark

[sabray]

Farley mowat might suggest backing it into a good mud bank. If it sacrificial water.
I'm just no help here. I liked the melted milk jug idea. If you got a butter knife hot enough maybe you could batter it all well enough. It probably cracked for a reason. If I were battering it up u might look at why it cracked there what's holding it in place . Some point is going to come along and you'll want to replace it. So maybe you get to choose when and where.

[peghall]

What KINDS of plastic? And for how long? PVC is plastic...PP is plastic...Lexan is plastic...Eisenglas is plastic...the list is endless. The fact that something will stick to one of 'em--or even most of 'em--does not guarantee it'll stick to all of 'em. And even if it does, is it permanent? Nobody's come up with anything yet that will bond to PE permanently...3M came out with some stuff about 10 years ago that was supposed to...and it did...but only for a few weeks.

[sww914]

I've welded it successfully on kayaks and car bumpers. I took a class and had the special tool for the bumpers, on the kayak I used a propane torch to pre-heat the plastic and I found shoe that fit my butane soldering iron. For a scrap of plastic to weld into the gap I trimmed a bit off of an edge that wasn't necessary. If you need a scrap you can install another access plate and use the part that you've removed as material. You can tell if it's PE or PP, one floats in water and one sinks but I can't remember which is which.
I tried special epoxy to repair an RV water tank, that's a load of crap. It worked for a few weeks and the original design flaw reappeared. What a waste of time & money. I'd rather get my eye tattooed than do that again.

[forsailbyowner]

I repaired mine with a pencil torch and high strength hot melt glue sticks. Th e glue sticks are made of polyethylene and did a fine job of it. Just weld like gas welding , starting a puddle and feeding the glue stick into the puddle as you progress with the weld.

[Beach Cruiser]

Take a look at West Systems G/Flex 655 epoxy. It is formulated for plastics. They show a video of a kayak they cut i half and epoxied back to together. I used it to repair a crack in the salon window of my catamaran.

[boatman61]

Mark... the butane torch will be to fierce... what you need to get hold of is a paint peeling gun... the electric ones that look like a hair dryer... then cut the milk bottle into strips... heat the area round the crack with the gun till tacky then lay the strips one at a time and melt into the tacky tank... the bottle material will melt quicker than the thicker area so just build up a strip at a time....

[David_Old_Jersey]

Originally Posted by steamgoat

Why not cut a hole in the tank where the crack is and fit a round plastic tank access panel,the type they fit to clean out tanks ??

I like the access panel approach (as would fit in with Plan B - drop a flexible tank in ). Curved makes it awkward - but not insurmountable. I would be thinking of making an (epoxy?) collar to give something flat to fix the access panel to (could probably DIY something).

Score 1 for Beneteau if the water tank is easily removable

[MarkJ]

Originally Posted by sww914

I'd rather get my eye tattooed than do that again.

Thats one I haven't heard.




I'll check out the glue sticks idea too

[Bill Burgette]

Let me find that part number for you. I had a car with a plastic radiator and it cracked. I called 3M and they sent me a flexible epoxy that not only stopped the leak but withstood 15 PSI. It never leaked again. It was dark gray and stuck like glue. I'll post back when I find it. I've got it stored somewhere on my hard drive.

[MarkJ]

Originally Posted by David_Old_Jersey

Score 1 for Beneteau if the water tank is easily removable

Yeah, its under the forward cabin bunk so its just a few screws to take the bed boards out and 2 bolts, plus the hoses etc.

[allanpeda]

Originally Posted by David M

Google "Polyethylene water tank patch". There are plenty of sources to choose from.

I also found this...
http://www.mrstickys.com/products/POLY-TANK-REPAIR-KIT-(MANUAL-MIX).html

I would rough it up with some 40 to 60 grit to get a better physical bond.

The instructions also mention the flame pre-treatment noted as essential in the video above.

[Ziggy]

Originally Posted by Astrid

It might be worth looking at this site as well for some more ideas:
Plastic welding, plastic welding tools, plastic welding equipment, kits, rods and supplies.

I think plastic welding is the best way to fix a crack in polyethylene.

Originally Posted by Astrid

Your best bet would be to patch it rather than attempt to fill in the crack.

1. drain the tank.
2. Roughen up the area around the crack or tear and drill a small hole at each end of the crack as an arrestor.
3. cut a fiberglass material patch larger enough to cover the crack with a 5cm margin
4. coat the area around the crack liberally with epoxy so that the coated area is slightly larger than the patch.
5. Lay the patch in place and coat the patch and surrounding area with epoxy.
6. allow to cure and set before refilling the tank.

Flexible epoxy (like West System G-Flex) may work. An essential preparation step to ensure adhesion is to flame treat the plastic (see here for instructions). Without flame treatment it's likely the repair will fail.

[Charlie]

Originally Posted by MarkJ

Well, at least I have found the problem!!

One of my plastic water tanks has a 3 cm (1.5 inch) crack in it and its piddling water when its full.

I 'fixed' it a few months ago with a hard epoxy putty. However the instructions must have been wrong

What would you do to fix it 'properly'?

I am thinking a nice splatter of my silicon sealant. But knowing boats I thought I better ask....


Mark

one more idea here. cut a rectangular hole in the tank. Take 2 pieces of 1/4" starboard (HDPE plastic) heat it to conform to the shape of the tank using a paint strip heater. Make sure that one piece can slip inside the rectanuglar hole. Take the two pieces of plastic and stack them on on the other and clamp them . Then drill pilot holes (that don't go all the way thru) for stainless steel screws and place the screws in the plastic using screws of a length that they don't penetrate the bottom piece. Remove screw and find two holes on opposite sides of the plastic and continue the pilot holes all the way thru the plastic. Use one piece of the plastic as a template and drill over size holes in the tank so that the screws will not grab the tank. Next on the holes that were drilled all the way thru insert a piece of strong fishing line down one hole in the plastic and up the other so that it supports the bottom. Feed the fishing lines thru the tank and thru the top piece of plastic. Use the fishing line to apply tension on the plastic while inserting screws. When all but the last two holes are done pull the fishing line thru. Apply the last two screws.

On re read you may want to insert a gasket in the sandwich.

I would think you could source all of this stuff locally but if you need some 1/4" plastic let me know and I can ship you some small pieces for the cost of shipping.