Fresh Water Repair

[parkgt]

I believe the success of the patch will depend on the workmanship achieved doing the welding. This welding project is not easy. I would suggest getting extra LDPE sheet stock and practicing before starting in on the tank. It will be easy to get too hot and melt through the tank or not get hot enough and have a failed cold weld. If this is the bottom of the tank and requires welding overhead the difficulty factor goes way up. Good Luck and let us know how this turns out; pictures would be great.

[booster]

Originally Posted by Rlum

Hi:

My tank definitely have square corners. So I am guessing LDPE? Thanks for insight. I have to be careful when patching this. Do not want to melt the existing tank material. It is just a hair line crack about 1-1.5 inches long. Barely can see it. Only when water is in tank, can I really see the leak. Am planning patching the crack with a width of LDPE material. After which, will cut a piece of stainless steel mesh about 1-1.5 larger in all directions to provide structural to tank patch. Weld the patch so it is totally encapsulated in LDPE. Hopefully, this will prove to be robust?


Thanks for information!

A couple of points.


You have to melt the tank material or the new material will not meld to it and just fall off.


You need to open the crack up and weld to the bottom or it, or very close to the bottom, or it will just propagate back up through the patch at first stress and over time.


I can tell you that it will be very difficult to imbed a mess into the tank by welding alone. I have seen it done, with varying results, by heating the mesh and then sinking it into the base material before welding in the open areas, but it is a high skill thing to do, I think.


I think for long term durability best results, I would look at a support under the tank tied to the van body or frame to prevent the flexing from the water weight and motion, as that is what caused the problem in the first place.

[Rlum]

Originally Posted by booster

A couple of points.


You have to melt the tank material or the new material will not meld to it and just fall off.


You need to open the crack up and weld to the bottom or it, or very close to the bottom, or it will just propagate back up through the patch at first stress and over

I can tell you that it will be very difficult to imbed a mess into the tank by welding alone. I have seen it done, with varying results, by heating the mesh and then sinking it into the base material before welding in the open areas, but it is a high skill thing to do, I think.


I think for long term durability best results, I would look at a support under the tank tied to the van body or frame to prevent the flexing from the water weight and motion, as that is what caused the problem in the first place.

Are you saying? I should stick a flat head screw driver into crack and enlarge it? It is a hairline crack. I was planning on welding a piece of LDPE onto the crack about 1/2 to 1 inch on each side. Thin out a bit. Place the mesh on top and cover entirely with more LDPE to encase it. The mesh will be about 1.5 to 2.0 inches from the entire crack. I am looking at the mesh providing support to the floor of the tank. Looking to mesh strengthen the floor. The tank is well supported since I have tried to wiggle but to no avail. I will look at providing additional support to it. I am sure I can come with something.

[booster]

Originally Posted by Rlum

Are you saying? I should stick a flat head screw driver into crack and enlarge it? It is a hairline crack. I was planning on welding a piece of LDPE onto the crack about 1/2 to 1 inch on each side. Thin out a bit. Place the mesh on top and cover entirely with more LDPE to encase it. The mesh will be about 1.5 to 2.0 inches from the entire crack. I am looking at the mesh providing support to the floor of the tank. Looking to mesh strengthen the floor. The tank is well supported since I have tried to wiggle but to no avail. I will look at providing additional support to it. I am sure I can come with something.

The normal way of crack repair in many kinds of materials is that you have to get rid of crack entirely or it will repropagate. In a relatively thick thing like a plastic tank that would mean grinding out the crack wide enough to weld in a piece from the bottom of the crack to the surface, often in several layers. It is about the only way to get rid of any propagation points.


Just can't you can't wiggle the tank doesn't mean it won't sag on the bottom when full of water and that sag is a tension stress flexor on the entire bottom of the tank, which can cause cracks. Just the fact you have a crack would indicate you likely have a high stress area. Putting a support across the bottom of the tank to keep it from flexing is the fix for that issue.

[dicktill]

If at all possible, remove the tank so that you can turn it upside down and work on it "from above".

Plastic welding is not all that much like metal welding in that you do not get (in my experience with ABS) a nice molten puddle you can manipulate. Instead you get a taffy like gooey mess.

Good luck, Dick

[Rlum]

Originally Posted by dicktill

If at all possible, remove the tank so that you can turn it upside down and work on it "from above".

Plastic welding is not all that much like metal welding in that you do not get (in my experience with ABS) a nice molten puddle you can manipulate. Instead you get a taffy like gooey mess.

Good luck, Dick

Thanks for info. If I were to remove the tank. I would just replace it with new. Am planning on doing this upside down.

[booster]

Originally Posted by Rlum

Hi:

My tank definitely have square corners. So I am guessing LDPE? Thanks for insight. I have to be careful when patching this. Do not want to melt the existing tank material. It is just a hair line crack about 1-1.5 inches long. Barely can see it. Only when water is in tank, can I really see the leak. Am planning patching the crack with a width of LDPE material. After which, will cut a piece of stainless steel mesh about 1-1.5 larger in all directions to provide structural to tank patch. Weld the patch so it is totally encapsulated in LDPE. Hopefully, this will prove to be robust?


Thanks for information!

If you can still get a new tank, I would do that in a heartbeat if it were me. Repairs like this are always difficult and hard to predict success. As Dick said, having the tank out and upside down would help get better results and would also allow you to get it into a plastic fabricator shop for a professional repair where they would be using experienced welders and very good tools. Removing the tank would give you more choices and fall back positions, and hopefully better reliability.

[GeorgeRa]

You could consider drilling the crack out completely and insert an expandable rubber/stainless steel plug, assuming that the crack is far enough from the edge. https://www.mcmaster.com/rubber-plug...pe~expandable/

[Rlum]

Originally Posted by GeorgeRa

You could consider drilling the crack out completely and insert an expandable rubber/stainless steel plug, assuming that the crack is far enough from the edge. https://www.mcmaster.com/rubber-plug...pe~expandable/

Thanks for idea. My crack is near edge or right angle about 1/4 inch away. I think Booster is right. Something happens when driving and water is slooshing around. Probably hitting area in strange way.

I will repair the crack with plastic welding and metal mesh. Try to get a good melted joint. This will be difficult since first time and will upside down. Check for leak if no leaks. I will enhance the support of this corner somehow. Probably of couple of metal straps?

If all fails, I can always purchase a new tank. I did not call the PW dealer so do not know if they even available. It is a custom tank since avoids the OEM sway bar by going below and up behind it.

[GeorgeRa]

You could consider stainless steel tank, I have custom fresh and grey tanks. Cost was comparable with custom polyethylene tanks with steel, powder coated frames.

[Rlum]

Originally Posted by GeorgeRa

You could consider stainless steel tank, I have custom fresh and grey tanks. Cost was comparable with custom polyethylene tanks with steel, powder coated frames.

Thanks again for fine suggestions. The tank I have is quite complicated. It looks like a large U shape with 90 degree angles. Designed by PW to fit precisely around the Ram chassis and sway bar. I believe having a custom fabricated tank from stainless would be pretty expensive. Maybe around 1500 or more. A repair of some sort with additional supports would probably give me several years of dependable use? At least what I am hoping.

[GaryG]

You CAN reliably glue polyethelene. Use this stuff: https://www.amazon.com/655-8-Pre-Thi...23118372&psc=1

You will want to first go over the area lightly with a torch or a lighter. The heat alters the long chain polymer and makes it more receptive to the epoxy. Then sand lightly just enough to give it a tiny bit of texture. Mix the epoxy and spread a thin layer around the area of the repair. Once spread, place a small piece of fiberglass or carbon fiber sheeting on the uncured epoxy. Let it cure. Then mix some more epoxy and cover the cloth completely. Done. Sealed.

I did this on a very difficult area to repair on the inside of a poly kayak and it worked perfectly. This thickened epoxy is one of the best products I've ever used. Here's a demo on how well it works:

https://www.youtube.com/watch?v=WCS0qrD3MQY

[yogi22]

Originally Posted by Rlum

Thanks, I have searching but unable it. Funny when they come up, we read and forget them. Now I would like information, cannot find it? Just like my tools, I have them somewhere but cannot find when necessary?

Thanks

Here is a link to a posting I made that told of my success with "Gloozit". Gloozit is a Canadian product but I am sure that similar stuff is available everywhere. Worked for me!
https://www.classbforum.com/forums/f...air-10804.html

[Rlum]

Thanks everyone. I just completed the repair with a Harbor Freight plastic welder. Purchased LDPE sticks from Amazon.

It was not easy. Difficult to see unless water was filled. Also working against gravity. Heated the crack which was 1/4-3/8 inch. Allowed the LDPE tank material to turn clear. This is when I know the material is ready to bond. Used a small screw driver to push into the material in about 30 seconds. when material turns back to opaque, it is no longer bondable but maleable. Hold in place for another 30 seconds or so. Ad some weld rod material to divet. Only add 3mm to 5mm increments since material must turn clear to bond. Push in with small flat screw driver and hold for another 30-50 seconds. Repeat this step until the material is flush with untouched tank. Yes it takes while. Check for leaks.

Fill tank and check for leaks. Yes it was still leaking. I took my compressor with air gun. Blew into the leaking area to find exactly where it was. I knew it was the correct crack when bubbles appeared thru the translucent tank.

Drain tank and repeat when material is dry. Make sure you have good lighting. I used my overhead light and could see pretty decently.

Now testing, lets see if the repair works. Have not install mesh yet. The mounting nut on closest bolt to the leak seemed lose. I was able to tighten it by about 1/2 to 5/8 inch. This might have contributed to crack since the tank might have movement?

[Rlum]

Originally Posted by GaryG

You CAN reliably glue polyethelene. Use this stuff: https://www.amazon.com/655-8-Pre-Thi...23118372&psc=1

You will want to first go over the area lightly with a torch or a lighter. The heat alters the long chain polymer and makes it more receptive to the epoxy. Then sand lightly just enough to give it a tiny bit of texture. Mix the epoxy and spread a thin layer around the area of the repair. Once spread, place a small piece of fiberglass or carbon fiber sheeting on the uncured epoxy. Let it cure. Then mix some more epoxy and cover the cloth completely. Done. Sealed.

I did this on a very difficult area to repair on the inside of a poly kayak and it worked perfectly. This thickened epoxy is one of the best products I've ever used. Here's a demo on how well it works:

Sounds good. I might used to embed the stainless steel mesh. How long does this stuff take to set? My mesh support will be fighting against gravity.

[GaryG]

Initial cure is 7-10 hours. Full cure is 24 hours. I guarantee you will use this products for many different repairs. I'm on my second kit. Full instructions for various repairs including the heat treating I mentioned. I don't think you need stainless mesh, but this stuff is pretty thick. If you have doubts, perhaps just support the mesh with something tiny and disposable wedged against it for the cure.

[alschott]

Usually drilling a small relief hole at each end of the crack will help de-stress the crack. I used the Harbor Freight welder on a motorcycle luggage carrier and it was fine.
May also want to place a support under the tank to carry some of the water weight.

[Rlum]

Originally Posted by alschott

Usually drilling a small relief hole at each end of the crack will help de-stress the crack. I used the Harbor Freight welder on a motorcycle luggage carrier and it was fine.
May also want to place a support under the tank to carry some of the water weight.

I would be afraid to drill a stress relief hole. The crack is so small. I can barely get a small flat head screw driver into it. I know it is there because compressor can push air thru to create water bubbles.

I found the bracket nut supporting the tank was not as tight as others. I tighten it about 1/2 inch. PW has lots of support bands. These metal bands are about 3.5 inches wide and there are three. So support is pretty good. Once I determine leak has been resolved, I will install the stainless steel support mesh.

Thanks

[Rlum]

Update to my repair issue. Found local plastics repair shop. Mostly a manufacturer of plastic tanks, etc.

MGM plastics suggested I come in for an evaluation. Great company and people Very helpful. The did a plastic welding repair but said long term most of these tanks will fail. Why? The tanks are inadequately supported and all kinds of stress and torsion forces occur on the plastic when filled. He said repair was not guaranteed since the tanks was not removed for repair. Either way it was just a band aid job. I said no problem and I was willingly to risk it. They used a grinder to sand surface. Used a professional plastic welding gun. It had a small compressor and heat source. Temp and pressure controlled. Simultaneously heated the tank surface and welding rod while melting the two together. They do not add wire mesh, etc. Said nothing will bond to PE except heat and same material. Owner said he does about 5/week from RV dealers. Most of these tanks fail just past warranty period. Looks like I will be filling water tank upon arrival at the campgrounds hence forth. Really learned a lot about PE.

[Rlum]

Originally Posted by GeorgeRa

You could consider stainless steel tank, I have custom fresh and grey tanks. Cost was comparable with custom polyethylene tanks with steel, powder coated frames.

I am curious who you had make your tank, etc. What kind of vendor does this.
More interested in frame support.

Thanks