Fresh Water Repair

[Rlum]

Hi:

I have small crack (1-1.5 inches) on my fresh water tank. It is even very difficult to see so did not take a picture. It is very close to an inside corner. nothing missing just a hairline crack.

Any suggestions on how to repair this? I read that polyethylene cannot be glued. I think this tank is made of this stuff. Looking at plastic welding. I want to repair without removing the tank since the leak is very accessible. Only think is the crack is on bottom on tank so glue, sealants require support?

Thanks everyone!

[mkguitar]

I remember seeing another similar concern in a thread about 6 mos ago if you feel like searching


mike

[Rlum]

Originally Posted by mkguitar

I remember seeing another similar concern in a thread about 6 mos ago if you feel like searching


mike

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

[GeorgeRa]

https://www.classbforum.com/forums/f...eak-12611.html

Very difficult to reliably glue polyethylene, best is welding. Perhaps two steps fix could be a good option.

1. Weld the leaking crack and sand it flat.

2. Add large piece of ~1/4” polyethylene (or HDPE) and weld it on the edges to the tank to strengthen the tank’s bottom.

Is your tank translucent?

[Rlum]

Originally Posted by GeorgeRa

https://www.classbforum.com/forums/f...eak-12611.html

Very difficult to reliably glue polyethylene, best is welding. Perhaps two steps fix could be a good option.

1. Weld the leaking crack and sand it flat.

2. Add large piece of ~1/4” polyethylene (or HDPE) and weld it on the edges to the tank to strengthen the tank’s bottom.

Is your tank translucent?

The crack is so small, I can barely see it. I am thinking try some adhesive over the crack. i had to mark crack since could barely without water. I have read polyethylene has nothing which adheres/bonds to it. Thinking of more conservation solution. If it does not work out, I will do the plastic welding. I bought the plastic welding iron and rods today.

Yes, the tank is translucent.

[booster]

Originally Posted by Rlum

The crack is so small, I can barely see it. I am thinking try some adhesive over the crack. i had to mark crack since could barely without water. I have read polyethylene has nothing which adheres/bonds to it. Thinking of more conservation solution. If it does not work out, I will do the plastic welding. I bought the plastic welding iron and rods today.

Yes, the tank is translucent.

Yes, polyethylene does not glue well, especially in areas that move like the tank bottom. As George said, welding is best, but it will be tough at home unless you really know how to do it.



The crack is now contaminated so you can't just fuse it and expect it to hold as the weld will be contaminated. It is nearly impossible to get to the inside to clean the area to keep any through weld from being contaminated. A pro might be able to cut out a section big enough to clean around it or know how to keep contamination out by staying a bit shallow, but would be hard to do. I have seen lots of industrial process tanks fixed, but they always cut out a piece and welded in new, from both sides in most cases.


If there is any amount of crack left anywhere in the welded area it will likely propagate very quickly as that area obviously is moving around from the liquid weight.

[GeorgeRa]

If you are going to use adhesive try to get adhesive promoter like Eastman 550-1.

[Rlum]

Originally Posted by GeorgeRa

https://www.classbforum.com/forums/f...eak-12611.html

Very difficult to reliably glue polyethylene, best is welding. Perhaps two steps fix could be a good option.

1. Weld the leaking crack and sand it flat.

2. Add large piece of ~1/4” polyethylene (or HDPE) and weld it on the edges to the tank to strengthen the tank’s bottom.

Is your tank translucent?

If the tank is translucent. Does this mean material is high density Polyethylene?

[Rlum]

Originally Posted by GeorgeRa

If you are going to use adhesive try to get adhesive promoter like Eastman 550-1.

I am leaning towards not using an adhesive. Been going back and forth since this is my first repair.

I am thinking now of doing a plastic weld with some stainless steel reinforcement mesh. Looking at using a low density polyethylene weld material? Just not sure what the tank material is? Trying to find out. I think it is a high density polyethylene?

[Rlum]

Originally Posted by booster

Yes, polyethylene does not glue well, especially in areas that move like the tank bottom. As George said, welding is best, but it will be tough at home unless you really know how to do it.



The crack is now contaminated so you can't just fuse it and expect it to hold as the weld will be contaminated. It is nearly impossible to get to the inside to clean the area to keep any through weld from being contaminated. A pro might be able to cut out a section big enough to clean around it or know how to keep contamination out by staying a bit shallow, but would be hard to do. I have seen lots of industrial process tanks fixed, but they always cut out a piece and welded in new, from both sides in most cases.


If there is any amount of crack left anywhere in the welded area it will likely propagate very quickly as that area obviously is moving around from the liquid weight.

I am leaning towards a plastic weld with low density polyethylene. I think tank is high density polyethylene. Will probably sand and clean surface with isopropyl alcohol. Go about 1 inch around crack if I can. Seal crack first. Place a piece of stainless steel mesh extending about 1-1.5 inches from the crack in all directions if possible. I believe you are correct. If the area is not reinforced, the crack will probably increase over time. Better to reinforce now instead of doing a larger repair later?

[GeorgeRa]

I think most molded tanks are made from polyethylene which often is translucent. I would think that good weld should last long time unless it is exposed to flexing.

Some of the Gorilla tape claims to adhere to polyethylene, a few layers of this tape could provide sufficient reinforcement vs SS mesh.

https://www.usplastic.com/catalog/it...x?itemid=24504

[Rlum]

Originally Posted by GeorgeRa

I think most molded tanks are made from polyethylene which often is translucent. I would think that good weld should last long time unless it is exposed to flexing.

Some of the Gorilla tape claims to adhere to polyethylene, a few layers of this tape could provide sufficient reinforcement vs SS mesh.

https://www.usplastic.com/catalog/it...x?itemid=24504

How would I know for sure if polyethylene or polypropylene?
Are the welding rods interchangeable? I have the polypropylene already. Can I use polypropylene rods on a polyethylene tank material?

Thanks

[booster]

Originally Posted by Rlum

How would I know for sure if polyethylene or polypropylene?
Are the welding rods interchangeable? I have the polypropylene already. Can I use polypropylene rods on a polyethylene tank material?

Thanks

There was another discussion on this a while ago on this forum and IIRC there are a couple of different styles of polyethylene and one is much harder to even weld than the other. There was a link to article that describes it all. It would probably pay to try to find that other discussion as it covered a lot of details I think.

[Rlum]

Originally Posted by booster

There was another discussion on this a while ago on this forum and IIRC there are a couple of different styles of polyethylene and one is much harder to even weld than the other. There was a link to article that describes it all. It would probably pay to try to find that other discussion as it covered a lot of details I think.

Thanks. On Google, most forums talk about repairs. To use LDPE to repair HDPE is OK. Melting temp is 100C for LD and 130C for HDPE. I will probably use the LDPE with stainless steel mesh. Just ordered from Amazon. Ordered a piece of HDPE sheet to practice a couple of times before going at the tank.

Hopefully, the repair will be good and last years to come.

[GeorgeRa]

HDPE comes in sheets, it replaces teak in the marine world, it is often used in outdoor equipment due to its resilient to UV. It usual comes in opaque black, white or color. Cutting boards are often made from HDPE.

HDPE tanks are welded not molded. I use HDPE in my conversion in lieu of wood.

It is best to match high density or low density polyethylene with corresponding welding rod.

[Rlum]

Originally Posted by GeorgeRa

HDPE comes in sheets, it replaces teak in the marine world, it is often used in outdoor equipment due to its resilient to UV. It usual comes in opaque black, white or color. Cutting boards are often made from HDPE.

HDPE tanks are welded not molded. I use HDPE in my conversion in lieu of wood.

It is best to match high density or low density polyethylene with corresponding welding rod.

When you weld HDPE to HDPE tank. Do you just wait until the stuff smokes a bit and back off heating element? Hold rod in place with some force until it cools/adheres? I am afraid I will heat too much and weaken my tank?

Thanks

[GeorgeRa]

Originally Posted by Rlum

When you weld HDPE to HDPE tank. Do you just wait until the stuff smokes a bit and back off heating element? Hold rod in place with some force until it cools/adheres? I am afraid I will heat too much and weaken my tank?

Thanks

Don't have much experience with welding but smoke is not good, rod needs be soft and its surface melting. Having a heat with a rod feeder is reasonbly easy.

[Rlum]

Originally Posted by GeorgeRa

Don't have much experience with welding but smoke is not good, rod needs be soft and its surface melting. Having a heat with a rod feeder is reasonbly easy.

Thanks!

I think the patch will hold. The important aspect of this repair the reinforcement with stainless steel mesh. I believe the weight of water banging against this portion of tank has weakened the hdpe? I will be reinforcing the corner with mesh about 1.5 inch past the crack. First time so wish me luck.

[parkgt]

If the tanks was blow molded it is HDPE if it was Rotomolded it is LDPE. Square cornered tanks are typically LDPE Rotomolded. Blowmolding HDPE is used on more cylindrical tanks. Blowing the preform into square corners thins the plastic too much. Rotomolding does not have that problem.

[Rlum]

Originally Posted by parkgt

If the tanks was blow molded it is HDPE if it was Rotomolded it is LDPE. Square cornered tanks are typically LDPE Rotomolded. Blowmolding HDPE is used on more cylindrical tanks. Blowing the preform into square corners thins the plastic too much. Rotomolding does not have that problem.

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!