Backyard Aquaponics
A place to discuss aquaponics

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Did you try a soldering iron and some HDPE scraps.. I would do that first..

In the least you should be able to decrease the size of the hole and thus make it easier to actually fill..

I cant see most anything sticking properly...

Buy a cheap soldering iron with the larger tip and grind it to a smooth flat that can be used to "Wipe" material into the holes..
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As you've already determined, very little sticks to p.e. I do not know if either product is available in Australia, but if I was patching liner here, I'd use what we call 'Tuck Tape' for a short term fix. It is used to seal vapour barriers in construction, is red, cellophane type top layer, and an adhesive that will stick to anything, including the hdpe vapour barrier. For a longer fix, I'd either heat weld, or use a 3M spray adhesive called Super 90 that is (or at least used to be) designed to adhere to hdpe. The super 90 is like contact cement, you coat the liner and the patch, let it dry, then stick the two together. Get it right the first time, because there is no peeling it off to try again.
Good Luck.

I found this stuff on the net, I have seen people use it but I don't know if it is fish safe?

welding is maybe to best bet but it will be hard to not burn more holes in the liner?

I would heat the mating surfaces up with a hot air gun and roll firmly over. It should stick as that is how large pond liners are made.

I have a commercial heat gun here I could lend you.

Sorry about the tommy tape that's mainly for wrapping pipe if its polyethylene use a patch of same material heat gun and rollerplastic welders use this method

Does the heat gun work on the liner? Is it a soldering iron? Or a hair drier type?

I'll try the duct tape, it'll probably fail, but I'll see how it goes first (it's supposed to work on swimming pools, I did some googling), then I might take you up on the offer Bernhard.

Thanks for your help guys!

This is the heat gun. I have been using it for plastic welding for about 10 years. Not tried it on liners yet but it can be used for that, I just need to get a flat nozzle for it.

Swimming pool liners are made from PVC which is easy to stick things to.

HDPE, LDPE, LLDPE are great liners to use but they all share one common disadvantage, namely they are an absolute dog to join without the right gear and even with the right gear to repair.

I don't know where the holes are but have you considered a mechanical fix? You would have to excavate the media but two pieces of plastic chopping board either side of the hole with rubber gaskets between the plastic boards and the liner all bolted together with 316 stainless steel bolts (and washers).

ColIum if you search you tube there are some good demos on repairing liners with the hot air welder and roller method

The first trick is getting the hot air gun (hair dryer won't cut it) the second is getting the technique.

One of those things that is relatively easy once you have the right tools and skills. Mind you I believe that because of the way PE oxidises you have to make sure that the area is abraided throughly so you get a good weld.

Stuart, you have nailed it here. It is the oxidation that makes PE so difficult to bond to. (actually the oxidative state, if i recall, but that's nitpicking.) PVC is relatively easy to weld, Although I've only done pipe and a little vinyl floor, ranging from 3-8 mm thick. PE is not as easy, and I wouldn't trust my work on 6 mil liner in pvc or PE. Just for fun I'll add 'try to weld 6 mil poly' to my list of things I'm trying to get to, but it'll be a (long) while before I do it.

Lastly, this may be a stretch, but the wikipedia page for hdpe lists a few adhesives that are used. Here are the logic steps I followed, all from the respective wiki pages:

Pressure-sensitive adhesives (PSA) are feasible if the surface is flame treated or corona treated. Commonly used adhesives include: Vinyl acetate copolymer hot melt adhesives.

Ethylene vinyl acetate (also known as EVA) is the copolymer of ethylene and vinyl acetate.

Hot melt adhesives, hot glue sticks, and top of the line soccer cleats are usually made from EVA.

Therefore, if you flame treat the surfaces, you should be able to glue with a hot glue gun. Flame treatment instructions are found at the bottom of this page:
http://www.westsystem.com/ss/gluing-pla ... lex-epoxy/

If you try it, let me know if it works. Otherwise, I may try it myself, sooner than the welding.

I can just see Column under his GB heat treating the liner when it let go. Covering him in muddy gravel and plants

That'll probably be me under the bed cursing and muddy and dirty.... Sadly.

The liner in the bed that I broke was one of the first I bought, and it's a lot thinner than the other DWC beds I built, it's closer to builder plastic, I don't like my chances of welding it without burning through. I know the difference in welding very thin steel, vs thicker steel, even with low temps, it's far trickier, I'd imagine the pond liner is the same.

I woke up to it this morning drained again. I think I damaged the uniseal, well I know I did when I was trying to beat it back into place (it was on a bit of an angle), and it just dumped the whole sump again. At least the fruit trees near it will be getting a good watering.

I bought some more uniseals, and I'll use it as an excuse to do some maintance on the bed. The gravity fed pipes were too small, and they would overflow before giving a good amount of flow between the DWC beds. So I bought some 90mm uniseals, and hopefully they'll arrive quickly.

I think the selley's epoxy aqua adhesive stuff would be similar to the west system stuff. I know from my fiberglassing days, it's tricky enough to find the regular stuff, and I wouldn't need much.

Moral of the story, don't put uniseals through wood that'd thicker than the uniseal, it ends with this.

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FWIW... there is another product that is used to seal glands in washing machines etc..
SCOTCH-SEAL 800, and it does stick to HDPE... and many outer tubs of such machines are made from HDPE..

I would again start with slivers of HDPE and a soldering iron, and then ensure no pin holes via a sealant layer..
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