How Annoying Is That?!

@noisette47

It is irritating to observe that some people’s ponds have a better level than others.

This pond was designed so that, when full, the water level is considerably higher than the lawn. Not that there’s much point to that, other than to create some kind of gravity-defying infinity pool effect; infinity being difficult enough to grapple with, but every bit helps.

Mysteriously, some years ago, the height dropped and is now resolute at the illustrated level (a drop (!) of some 28cm). There is no outside sign of leakage, no excessive damp anywhere, neither is there any evidence of a fissure.

Clearly, somewhere at that height, the surface has become porous and needs waterproofing.

Has anyone experience or preference for products such as G4, Black pond Paint, etc. (all of which get shockingly variable reviews)?

 

Assuming it's not a 'wick' effect perpetrated by the surrounding plants, I'd go for a sure and long-lasting solution...empty out and line with a decent liner. That attractive edge would help to disguise a neatly-cut liner edge stuck to the cuve with an appropriate waterproof glue. Something used for swimming pool patches or roofing glue, perhaps?
I've been doing battle with one corner of my formal pond ever since it was constructed, after an over-enthusiastic cut to shape the liner into the corner. No amount of patches and/or waterproofing products have made more than a temporary difference.

 

My pond level has been dropping fairly quickly all summer, I think it's a leak in the filter and waterfall system but I can't work out where it is.
Spent most of the summer looking fo damp ground, when it was dry, but not found the leak yet.

 

What about transpiration by the pond plants? We notice that if we remove some of the taking over plants the water level stays up.

 

Schadenfreude notwithstanding, I am very sorry to hear of your having had to fight your corner!

Your suggestion of a liner (rather than paints or polyurethanes which are often reported as failing) appeals to me.

Do you think – since everything below the described line has been “rock-solid” for over a decade – that I might get away with gluing a strip all around the periphery (it is not a big pond) starting, say, 15 cm below the offending line and, as you suggest reaching up to the “attractive” edge? Like this:

 

Your problem with the suggested strip is that you need a perfect seal all the way around the perimeter otherwise it will still leak out at the join level. With a full liner as @noisette47 suggests, even if the edge glue fails, you have an impermeable layer all the way up.

 

Looking at the picture I'm guessing you can't see the back side of the pond from the outside?
If you could locate the leak I agree just some type of pond sealant could be a fairly easy fix.
Does the water level continue to fall below where it is now?

Depending on what you have in the pond taking every thing out in order to add a liner is a lot of hassle imo but if the leak is low down its probably the only option.

What is the pond made of? Fibreglass? Plastic?

 

No. I tried patching mine, as mentioned above. It doesn't work, at least with any of the products I used to glue the patch, or for very long. Lining the whole thing will give you peace of mind for decades. Butyl and EPDM come with something like a 50 year guarantee

 

I know pond product suppliers sell all sorts of stuff, but I don't know if any of them work well, and I've never had to use them. I'm inclined to agree with @noisette47 about relining the whole thing. If the existing liner is old, there can easily be deterioration. The fact that it's against a concrete edge, or something similar, may have caused extra abrasion too. Most pond liner can be obtained fairly cheaply, depending on what you prefer. My ponds have always been for wildlife though, so they don't have vertical sides, and straight edges, so the poly types are fine. Butyl may be needed due to that shape, in order to get a neat finish.

I'm more curious about all the pale 'green' layer on the surface though. What is that?

 

@fairygirl ,duckweed perhaps.

 

Thank you all for your “in” valuable, in-depth contributions. Food for thought and fertilizer for much discussion here within the lawn but out of order.

Yes, true, but see below.

No, that level is stubborn and resolute.

The structure was made 27 years ago in concrete – no lining – treated with, I think I remember, G4. This held for some 15 years.

I fear I have allowed an opaque surface to distract from a hidden, unfortunate depth. The shape is much more complicated than I let on, but I now owe you some transparency: the unfathomable abyss in the excellent representation below was due to (mis) information alluding to the fact that locally increased water pressure would make the koi carps grow exponentially and delight the children of the time in proportional measure. The carps may have been koi, but the herons were not and, after a few years, our pond became a favourite location for their elegant aviation, and rivalling Rick Stein’s famed gastronomic oasis in Padstow. Many tears were shed, as our multicoloured treasures from Japan were brazenly returned, for all we know, to their country of origin from where they had probably been illegally imported.

All this to say that the shape of this pond was at the time regarded as a liner’s arch enemy. Perhaps you disagree? And yes, peace of mind – chance would be a fine thing – but Voltaire says it doesn’t exist, and we all know his views on gardening.

Yes, Noisette is right. She always is. That’s the infuriating thing.

The pale ‘green’ layer is an optical illusion, pale only in comparison to the incredibly green grass, far greener than any of the neighbours’. It is in fact duckweed, another bottomless mystery of our garden, as it materialises without explanation or origin, although I have recently seen snippets of a new series on the BBC called Solar System beautifully, if stoically, presented by Professor Grin, and I have now come to realise that this “pale” intruder must be coming from hitherto unsuspected outer regions some three hundred billion kilometres away. What a pity the herons aren’t interested in that!

 

The constant lower level does seem to rule out diversion by the plants. Trust you to have a unique shape! Had it been a 'box' shape, it's no longer a challenge, as the liner companies can produce heat-welded liners to order and to spec, which fit neatly into the hole. I've no idea whether they'd be able or willing to do that with a non-standard shape, or at least do it for less than several thousands of £££££s. Breaking it down into two component parts, the top would be easy, with a flap into the bottom part. You might have to just go the 'fold and stretch' route with the bottom part, though.
I can see why you want to try a strip solution. I really can't advise on a reliable product available in UK. The French options are all rubbish. I'd favour something designed for swimming pools or roofing leaks, though.
Herons are a pain! We opted for no fish here but the gawky things still come up to raid the ponds for frogs, despite having a steady supply of carp, crayfish and amphibians in the nearby agri-lac.
I think you're over-estimating the distance travelled by your duckweed just a tad It will have come in on a heron's beak.....

 

If the level drops no lower the leak is obviously quite high up, concrete is porous so its probably a gap at that height in the coating.
Its done well in 27 yrs, I'd lower the level a foot or so and recoat up to the top.

 

If you do try using a band around the top, I would suggest builders' adhesive/sealant such as CT1, Sticks Like, Gripbond Pro or Acrypol to adhere to the concrete. CT1 is supposed to be very good. I like Gripbond Pro but it is very messy - keep white spirit to hand for cleanup.

 

There is a product called Isoflex which is marketed for porous roof coverings. It adheres to even wet surfaces, can be applied even below water and, if safe for fish , would be the answer to your desire to bodge up a liner otherwise ready for replacement.
However its not, being harmful to aquatic organisms, as per its Coshh sheet:
https://www.selcobw.com/media/files...mtaCqYOSCo_yqX7VcS1GjWWngXTSaIjfcC6fWc5zL7kNl