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How to seal a clay pond?

Hi everyone! Merry Christmas 😎

I created a trio pond project a few years back, had it looking wonderful with pond lining (many hundreds of dollars worth), was growing Lillies etc and it was all fabulous. But I had not reckoned on kangaroos jumping through the ponds at night; consequently the lining was ripped and useless! I am living rural on the south coast of NSW.

SO. I took the lining away and started researching what a "wilder" pond project would look like. I heard about Bentonite clay, read about it and reckoned it would work.

It didn't. The pond is clay so I do not know why the water eventually just ran away or underground or where ever it went!?

There are no large stones in the clay... can anyone assist?

I used 50.5 kilos of the stuff all over the empty dry pond...

What am I doing wrong? And is there another solution?

Thanks everyone (Pics are taking long to load...)

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Jewelleryrescue

Hi @JacqG

Have built a 100% water proof pond that is UV stable and all but in destructable.

Can I ask how deep is the pond?

What are the side walls made of?

Is there a concrete base currently?

50kg clay sounds like a small area pond? What are approx dimentions Just say 1m x 1 m round or sqare etc it is just a mental pic for me.

The solution part 1.

I would concrete in the base of the pond for a solid base Thickness of concrete is depth dependant on water depth. 75mm to 150mm If kangaroos using it for a foot wash 75 min.

Then depending on the side materials place a woven renforced mesh into the side wall cement floor join (inexpensive) and then paint a cement layer mixed with silasec a remake of bondcrete that is totally water proof and sets harder the concrete itself.

This concrete paint is is also good on water tanks with potable water.

I always thought it would add fire protection to timber too from embers but not direct flames as painted timber would get heated through the concrete when thin. I always wanted to try that i you have wooden structures.

So this idea is farm friendly and doable and cost effective.

Sound like a plan to you we can talk more details,

Plan B there is an Austrlian company that makes a polymere product that seals whole earth ponds when it is sprinkled ontop of the clay and earth.

A previously leaking /weaping pond acres big will stop leaking through hidden drain holes. But kangaroo paws might disrupt the base of the pond to leaking again. Cement wont.

JacobZ

Hi @JacqG,

I'm sorry to hear of the issues you're having with your pond.

There is almost certainly a gap in the clay that is allowing water to drain through it. Depending on the dimensions of the pond, 50kg of clay is probably not enough to create a thick enough layer to really seal the water in.

Unfortunately, this is outside of my expertise and is likely something you would need to speak with a pond builder about.

Allow me to tag @Dave-1, @Nailbag and @Noyade to see if they have any advice they can offer.

Jacob

Dave-1

Afternoon @JacqG

What a pain and have been there with ponds leaking as well.

I had an old style sandy concrete styled pond, it ended up have a few cracks in it due to age, things being dropped in it "kerplunk" and the water pipe for the house running an inch below the surface of the concrete....

I have given lots of thought to ponds leaking and what to do to stop it and how to as well. I want an outside stream that runs via solar but also can handle storm instances and absorb runnoff 🙂 I have chosen that pond liner you have mentioned but I will line the lined with large rounded pebbles, What I loose in height of the water I will gain in longativity of the lining as less damage should happen to it. If you have pebbles down even if the kangaroos come on back fro a drink or two it should stand up better.

With the Clay, you need to have a solid wall of clay, think probarly 20cm thick for a pond at a minimun. 50kg wont really work. Other clays that people use for dams may be an option depending on where you live, the walls and base just need to be thicker.

Dave

Nailbag

Sorry @JacqG this is also outside my area of expertise. The only thing close enough that I have built was just a shallow 300mm moat style pond in the front of a house I once had. I used an additive to the concrete mix and then applied a rubberised sealant to the inside walls. There are quite a lot of newer products now available on the market since my build 10+ years ago.

Nailbag

Jewelleryrescue

https://www.workshop.bunnings.com.au/discussion/comment/46535#Comment_46535

Hi @JacqG

Sorry your pond cracked @Dave-1 alot of people beginners at ponds under estimate the strength , water weight and reinforcing required to have a pond not crack. This includes me I had my learning curve too. I just built my biggest strongest pond ever but I still needed to allow water weight testing time before tiles added (Easier to see and find fail points, in exposed new concrete.)

Your pond is concrete and totally fixable by the way I am sure those cracks can be filled you may need some steel in the base and another 50mm of cement followed by Silasec and pure cement paint. To try reinforce possible weak points sight un seen. Bondcretes can be used into the admix to make sure things stay together . and would be good between the old pond base and the new. Bondcrete is like aquadere in its use but for cement.

Pro landscapers can use plastic pond shell and dig it into the ground is easest of all. I might have done this but my area needed a custom built shape.

Pond liners yes Some pros landscaper use them good for 5 years. I have being there done that too. Rarely will liners sit flat with out some sort of need to fold the quality plastic liner on itself creating crease lines where i seams to crack and leak from first and totally fail re 100% water proof Maybe the ideal shape for a flat liner is a dish shaped dug out ground pond with no corners and folds.

Swimming pool liners are custom shaped to the pool with seam sealed side to floor joins so last alot longer with thinner materials no stone in them either.

Rubber spray on shells To expensive for pros landscapers to use :

The next evolution is sprayed in rubber like compound on concrete or timber form work this makes a 4 to 5mm thick walled custom pond base Expensive but good and you wont hurt it with rocks in it, and standing on it like pond liner sheeting. But this can break down over time to UV you might paint it as a sort of sunscreen to slow this down

As for clay pond bases I have never hear of any that being successful I mean totally water tight unless it was treated with polymers as mentioned in farm ponds on that scale. I dug my pond into near pure ground clay this stuff you could pick it up and start making model shapes out of it but it fill in rainy days but it drain with in 24 Hours. So water will find it way. I suspect clay ponds will leak a percentage into the ground? Ok if you dont have to pay the water bills.

Just to give you some credentials as to a successful build. Pros landscapers rarly use due to expense and time to make. Lets face it they want to make faster bucks for a cheaper outlay in out thanks for your money.

9000L cement and brick pond no cracks

9000L Cement and brick pond built to last and not fail like under designed concrete ponds often do in earlier attempts as water is very heavy that is 9 tonnes of water on top of a cement slab need to get that one right first time.

So how thick should the concrete be for my pond.?

I used 300 mm thick double steel reenfored concrete for the cement base with half round fillet corners with mesh webbing to transition water weight/pressure gradually to brick walls , Gravity goes straight down so regular double brick walls are not under huge strain.

Will it fail? NO I build to have it out last me and beyond no short cuts on key structural projects. Back yard pools tend to be around 150 to 200mm in the base depending on the concreter.

Stage 1 is the top section of the pond build when I had less ideas of fishes needs. Gold fish where fine koi where wallowing in the shallows. I did have a 10mm thick aquarium glass front originally. To explain the wings of bricks in the pond. It looked good.

Stage 2 is the lower section Koi need a deeper cooler water for higher fishy happiness. Koi treated right can live 30 plus years thats longer than cats dogs and many pets and they do learn and remember people contrary to many peoples thoughts of brainless animals.

It was challenging marrying the two pond stages as I had to undo bricks and interlock them so it wasn't a Butt join doomed to a leak failure.

Cut some holes in the brick wings for better water flow also for fish interest rather than a box of water.

I fully filled the pond to test the concrete for 2 months Rock Solid is the verdict , Stage one is 15 years old stood the test of water and time, Now I am starting to add a purly cosmetic layer of glass tiles. AS why go to all this trouble just to look at concrete.

The Rendered looking coating is several layers of Silasec over the top of bondcrete sealing layers this stuff is pure gold as it is UV safe as all concrete surfaces. Totally water proof was my goal for a long lasting pond solution all else are fails.

This journey began in earnist as the first pond stage was painted with crommelin blue waterproofing made for ponds was not stated as UV proof. 2 years later and it peeled and failed. Never assume a product is UV safe unless they state clearly it is. So I was badly bitten.

MitchellMc

Hi @JacqG,

I just wanted to check in on how you are going with your project and whether we might be able to assist further.

As picked up on, 50kg of clay even for a small single pond is likely not enough to prevent water leakage. For a natural pond or dam, the clay layer should typically be at least 15 to 30 cm thick to effectively prevent water leakage. The exact thickness depends on factors like soil type, the pond's size, and the quality of the clay. It also needs to be compacted well to form a durable, impermeable barrier.

I'd imagine that with that amount of clay, you were only able to line the pond with perhaps a few centimetres of it. It might be worth recoating with a thicker amount. I do like @Jewelleryrescue's idea of creating a concrete-lined pond. Although more work you'll have a much better result when trying to retain water.

Another option might be to use prefabricated poly ponds such as the Aquapro 1200mm Rectangular Feature Poly Pond or AQUAPRO 910 Round Feature Poly Pond.

Let us know if we can assist further.

Mitchell

JacqG

https://www.workshop.bunnings.com.au/discussion/comment/47417#Comment_47417

Hi Michell!

My emails went to spam - so annoying so sorry for delay in answering questions on advice about my ponds.

So you are probably correct in that I did not put more than several cms of clay on the pond. I had been watching vids and others showed people ‘scattering' the clay on the surface of a filled dam as a way to seal it… so I thought 50ks would be enough on an empty pond set..

Cementing means the plants can’t grow; I had thought of that.. a lot of work and maybe a bit ugly… the kangaroos put their nails through the original very expensive liner I did buy from Bunnings - its a set of three ponds around 5mx4m all up, only 1.5m deep each one.

I will chk out the poly options you mentioned - will keep the group updated, many thanks Jacque

JacqG

https://www.workshop.bunnings.com.au/discussion/comment/46511#Comment_46511

Thank you Jewelleryrescue and apologies for not getting back with thanks - emails were in spam! So to answer your questions

The pond set of three is about 5sqm

each pond almost 1 m deep

clay, natural - had them dug while the machine was here, more or less three big scoops out of the ground.

No cement anywhere. The Bunnings man said 50k Bentonite clay was not enough although I have seen a vid where they scatter the clay over a filled dam. I used the 50k on the dry floor and around the walls.

If I use cement, plants can't grow can they? Your plan sounds good IF plants CAN grow...

Who makes the polymere product that seals whole earth ponds?

thanks for your help 🙂

JacqG

https://www.workshop.bunnings.com.au/discussion/comment/46535#Comment_46535

Thanks Dave-1 - the roos jump through at night with their long toe tails...I understand the pebble idea, for the base but what about the sides - they are round, natural clay ponds...I watched a vid where they scattered the bentonite over the surface of the filled dam...to stop the leaks and I also watched a guy scattering the clay over the dry edges of his dam...sigh!....when you say "the walls and base need to be thicker clay" do you mean the Bentonite clay?

thx

EricL

Hi @JacqG

Let me tag @Dave-1 to make them aware of your question. I believe Dave-1 was suggesting having a thicker clay wall up to 20cm thick. My proposal is to use @Jewelleryrescue's idea of using concrete and using pond sealer to make it waterproof. It is possible to put soil at the bottom of the pond so that plants can grow in it. How ever the soil needs to be deep enough so that the plants roots can grow deep in it.

If you have any other questions we can help with, please let us know.

Eric

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/86428#Comment_86428

Evening @JacqG

Yeah the walls and the base need to be much thicker, I think I said 20cm thick all around at a minimum. Pricey unless you truck in a load of clay for dams. With the pebbles (and I mean palm sized rounded rocks at the smallest 🙂 ) the ponds I was thinking of are shallow sloped as 20cm height for 40cm distance. That way they will stay in place and if you had a few layers of the stones on top of the plastic liner (have seen a bunch of videos lately with a soft underlay of some kind under the plastic liner) You will loose water space but hopefully no leaks.

Dave

Dave-1

Evening @JacqG

I just came across an install of a pond/stream type deal that looks like it would work for you in the Big blue F social media place 🙂

Have a look for "Ecosystem Gardener" and their reels will show you a large install of a stream/pond. You could definently take some of the steps especially the gravel at the base (Hadnt thought of that one) with rocks on top. Why not, the gravel wont absorb but will protect the lining from being punctured.

Dave

Jewelleryrescue

Hi @JacqG

Well here is another idea use a quality liner and then use a layer of earth/clay 100mm Layer of smooth stones and then lay house bricks seconds on top as a protective layer ontop of the base

Kangaroos could push bricks down thats why the 100mm buffer layer. But house bricks on there edge will lock into each other and with stand things standing on them. A double layer of bricks over lapping each other will be extra secure un cemented. If you wanted to cement /mortor them in it will be a concrete alternative.

Potted plants can be used in ponds. While they are in ponds they can be moved around too. People like putting in steps for pot plants to sit on to so various plants might like different depths.

There are also floating pot plant holders around as an option.

Polymer is the latst high tech way of sealing some pond types and can be used in juncuntion with clay on sandy floors.

Research Polymer dam sealer for the best one that suits you and the pros and cons re kangaroo /stock use vs water holding.

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