HDPE liner pin hole repair (How do I)

[Myrlin]

Hi All,

I started building an above ground koi pond, late last fall. It is not a pond yet, but is to the point where it holds water... mostly.

This is a pond that can be moved inside/outside for the summary/winter. I initially bought a liner that was cheap, and light made HDPE. It was the last package of liner the store had as it was late fall, and it had a hard fold in it at one corner of the liner in the package (folded not rolled), so I was not sure it would hold water. When I filled it full of water setup outside last fall It seemed to hold well, I'd left it in for a month, until I had 4" of ice, then I tore the pond down.

However now I'm sure I have a pin hole leak in it. This week, I'd set it up in the basement and had a 10" or so depth of water in it for a week to allow it to de-chlorinate. I'd temporarily put fish from a 130g (US) tank it it as I had to drain the tank and move it. The pond worked really well for that (it was actually one main reason why i built it, as I knew I'd be putting in a laminate floor)

However when I tore the pond down this morning, I noticed that the carpet I used to protect the liner was wet in the center of the area. I'd guess that at absolute most, a 1/4 of water had leaked out through a pin hole, over the week. Not enough to spread to the outside of the pond, when on a painted cement floor, and be notice. So none of the water was absorbed into the floor, and I'm confident it is a very very small hole (I've yet to try and find it),

When the pond is installed outside, I'd not be worried about the leak, it is dry where I live, and water loss will be a small fraction compared to evaporation. although I'd be worried about mold/rot in the carpet underlay.

But in winter when I move the pond inside, it will be a problem (I'll likely move it to the garage, but I sure would like have enough trust to keep it in the basement).

So, the question is, how do I/Can I patch a pin hole in the HDPE liner. Without guidance I'll try to heat/melt a small blob of HDPE and smear it on over the hole with a soldering iron. Or, perhaps heat to melting a small piece of liner itself with a heat gun and apply it like a band aid, and then melt around the edges of the patch with a soldering iron, and I'll let you know how I did it and how it goes. Please let me know if you have experience with this, and if you think that is reasonable, or if you feel a different approach is necessary.

Of course I could just get a different liner, and would go with the EPDM, but I'm otherwise pretty happy with the HDPE liner for the pond shape I have, which is 8 sided octagon, flat bottom and strait up sides. So I'd rather stay with that if I can get the fix to a point where I trust it.

Thank you,

Myrl

[Myrlin]

Okay, in the hopes it helps others in the future, here is what I tried.

I took 1/4" stove bolt (?) the one with the rounded head, and screwed that into my soldering iron.

I then took a stip of HDPE material (the tab piece you get on some buckets, that you have to pull off, before you can take the lid off). I think on this bucket it is HDPE.

I cut a corner of the liner off, then used the soldering iron to melt some of the strip onto the screw head an smeared it onto the liner.

Some notes:
- it is easy to melt through the liner.
- it smeared on easily enough.
- even with a thin coat it was not as flexable as the liner alone.
- It did seem to bond pretty well, with myself trying to pick it off with my fingernails
- even where I did quickly smear it on, without an obvious hole, when I inspected the other side there is a very small section where it looks like the white had melted through the black (a filled in pin hole).

So I think this may work, however I declined to use it as it seemed to me that the risk of making it worse was too high.

As mentioned the hole, if it exists is very very small. In fact crawling under the liner trying to see if I could spot a pin hole of light shining through did not show me where the hole is. So I'm just going to live with it during the summer as is.

Cheers,

Myrl.

[BWG]

Use a waterproof tape with advanced adhesives designed for long term use. Such as the Gorilla and Flex tape brands advertised on TV . Many others on Amazon.

I've personally used FlexTape and it's an excellent product.

[Myrlin]

Thank you for that BWG.

To re-inforce what you say, I did build a scale(ish) model of my pond, and I did have a small leak in the 6mil polyethylene (vapor barrier). I used some tuck tape (blue) on the outside of the poly, and it sealed up nicely. I've been using the scale model for about a 1/2 a year now as a "grow out" tank for my guppies. Funny, I did this as a quick and dirty fix on my model, I never considered it for the real liner.

I'd typed up a response on what I did try, but it is not showing... so I'll repeat that.
I cut a small corner off the liner, and tried to melt some HDPE (from a bucket lid pull tab) and quickly smear it on with a soldering iron (using a 1/4 inch bolt as a soldering tip).
it seemed to work okay, the melted on HDPE seemed to hold quite well. However, the part with the smeared on HDPE was not quite as flexable as the rest of the liner. it was not aweful, and the fix point where I think the hole was is bottom center of the pond and would lay flat

Unfortunately I found it was quite easy to burn through the liner. Even the place where I thought I got it with out smearing it on seemed to have a small speck of white that melted through the liner.

I'd guess I'd have a 60+% chance of fixing it, but rather than risk making it worse, I decided to put the liner in as is for the summer. I could not even for sure find the location of the hole, it is very small.

Having said all that, based on your response, I think I may go with the tape. Would you put the tape on the inside of the liner, the outside of the liner, or both?

Thank you

Myrl

[Myrlin]

Thank you BWG.

Funny thing is I built semi-to-scale at about 1:5 a small replica of my my pond. it is 8" tall, 18" or so long, and 10" or so wide. I wanted to see if the wood at a 1/4 or so thick would hold water pressure. and i used 6mil vapour barrier (LDPE?). I had a small leak in that too, which was easily seen. Without thinking I put tuck tape on the outside, and it has held for 6-8 months (and still holding) . the funny bit is, I never considered using tape on the HDPE of the real pond.

Anyways, a follow on question: would you put that on the inside, outside, or both?

FWIW, here is how my little experiment went, I tried this on a small piece of liner:

I took a soldering iron, and dropped in a 1/4" stove bolt for a soldering tip.

holding this to the hDPE quickly burnt a hole in it (say in 1 second or so)

I tried melting on a a bit of HDPE from a bucket lid pull tab. (I think it is HDPE). and then quickly smear a light layer onto the liner.

It seemed to hold reasonably well, with the pick it off attempt using my finger nail. however the liner at the location with the extra material was less flexible... not much less, but noticeable. Not an issue as the hole looked like it was in the middle of the flat bottomed pond.

At my test point, it did look like a small bit of the white pull tab material may have melted through, Im not 100% sure though. I think it could be made to work, however I've decided not to go with this method for fear of making my very small leak worse. When tried to look for the hole with bright light on one side, dark on the other I could not find it, so I was not sure where to try the fix anyways.

But I'll definitely try the flex tape and give that a try, I have some reasonable candidate spots for the leak, where the liner had hard folds when it was in it's package.

[coolwon]

Whatever waterproof tape,I would apply on the inside of the pond with the water

pressure assisting to keep it fixed.

[Myrlin]

So I just taped it up today. I used Gorilla waterproof Patch and seal tape, placed on the inside only, due to being afflicted by a case of lazy (& Coolwon said it would be okay :-) )

For those looking to do something similar. It does seem to stick pretty well to the HDPE liner. It can be pulled off (not much sticks well to HDPE, as far as I understand), and adjusted. Which I had to do as I did not realize the The film layer over the glue side had torn lengthwise and was not coming off the full width of the piece as I was applying the tape. that, it was only half exposing the glue side, until it tore out the edge about 1m (3ft) later.
I'd say it sticks similar to the Tuck tape on Polyethylene vapour barrier.

I suspect it will work well for the leak. I'll not really know until next fall when I tear down the pond and move it to the garage. Even then I'm not sure I'll know, as the leak was minuscule to begin with.

I may use it to cover the folds in the liner at the corners, for a cleaner finish. apparently it can be applied under water(?), so I may put a couple inches of water in straighten out the creases as best i can and apply it.

Thanks for the help,

Myrlin