ponds and streams

gregoryjohn(z4b/IL)September 26, 2004

Has anyone built a pond or stream using bentonite to seal it as opposed to rubber liner?

How do you all feel about using rubber liners knowing that the liner will disintegrate just about the time your garden starts looking its best?


Thank you for reporting this comment. Undo
edzard(3b Canada)

yes. I've used betonite and its associated products.
Rubber liners we've avoided, prefering heavy duty plastics that are cut and remolded to match the contours of the pond and streams.
Both products originate in the gas, oil and hazardous waste sectors and allow us to build waterfeatures that tolerate tonnage's of stone, --in bentonite, the more stone the better, and more importantly both materials allow islands and bridge footings (etc.) to be crafted.

Of the betnonite or HD plastics, the latter are the preference, with an unknown lifespan in the hundreds of years.

    Bookmark   September 27, 2004 at 12:13AM
Thank you for reporting this comment. Undo

If your talking about powdered bentonite used for grouting wells and bulking up cattle feed it needs to be used with some precision. It is an inert clay and should be used in combination with other clay soils either mixed with the pond's clay soil or layered under a layer of clay soil. One recommended practice is to till the bentonite into the pond bottom to a depth of six inches and cover with a layer of gravel or sand in traffic areas so as not to disturb the boundry layer.

Bentonite will obsorb water and expand in particle size by a factor of ten or more if I remember correctly, I've 100/1 but I don't believe it. It will have the consistancy of jelly. You would not want to use it in areas where you will be waiding, without some protection or you may cause a leak. You may also want to grout any dock or boardwalk post punctures into pond floor with bentonite. think of it as radiator stop-leak.

I have not tried planting in it yet and as long as your pond does not drop and dry then it should seal around roots and other punctures. If it drys it will crack and seperate but should reconstitute when it gets wet again, but may not flow back homogeniously, you will have to smear or add more.

I am still experimenting with the stuff because its just about the only option in my large 2/3 ac pond. I may have to drain and layer it with clay soil as soon as I can afford a skid-loader..

good luck

    Bookmark   September 27, 2004 at 12:26PM
Thank you for reporting this comment. Undo
Gorfram(7b W Oregon)


I would love to know more about the HD plastics you are using. How are they cut, remolded, and re-sealed? What kinhd of plastic are they, polyethylene or another polymer? How do they stand up to punctures, slashes, foot traffic and sunlight? Who are the manufacturers?


- Evelyn

    Bookmark   September 27, 2004 at 1:50PM
Thank you for reporting this comment. Undo
edzard(3b Canada)

don't ask for much do you??
treated Polethylene.
cutting? knife, scissors, cutting tools, and welded with the same material, which is possible past -50C / F... this is tundra, permafrost material made to withstand the heaving of winter clay soils of + 600%.
foot traffic? what is foot traffic? well,... we run horses, cattle, deer, elk, whatnot through the pond, the occasional backhoe during construction. For a nail, you'll need a hammer.

Sunlight?? now you have me baffled... who in anyone's right mind would not cover the bottom and sides of a pond ??... or are you saying a thread on pond construction is necessary??
but it is UV treated anyway as well as corrosive resistant, etc.

bentonite... there are several products that are sandwiched bentonite --Bentomax, etc. depending on application with different weep rates, from 9 to 99 gallons per acre day. The 'carpets' are a lot easier to install and require a minimum of 20lbs. per square foot weight to 5 foot depths, 30 to 50 lbs. for deeper applications.

    Bookmark   September 28, 2004 at 11:42AM
Thank you for reporting this comment. Undo

This isn't about pond liners as such, but it does touch on pond & pool construction & may interest anybody who's thinking of constructing a pond -
Click for site about using vermiculite concrete

    Bookmark   September 28, 2004 at 5:04PM
Thank you for reporting this comment. Undo
Gorfram(7b W Oregon)

"don't ask for much do you??"

Well, I *wanted* a detailed engineering survey of polymer performance in this application, but tried not to ask for that :)

"foot traffic? what is foot traffic? well,... we run horses, cattle, deer, elk, whatnot through the pond, the occasional backhoe during construction"

That would be the traditional Japanese Pond Elk, right? :)

I was actually thinking of the pitter-patter of little gardeners feet, which I think I can correctly gather is not a problem.

"Sunlight?? now you have me baffled... who in anyone's right mind would not cover the bottom and sides of a pond ??"

With water, you mean? Or with something opaque? Non-UV-treated polyethylene is both weakened and embrittled by UV radiation, and a nice cover of algae, koi and water lilies will slow, but not stop that. UV-treated HDPE should be fine.

BTW, did you mean to say that the HD plastics had the unknown lifetime to hundreds of years, or the bentonite sandwiches?

"... or are you saying a thread on pond construction is necessary??"

Heavens, no ;)

- Evelyn

    Bookmark   September 28, 2004 at 6:17PM
Thank you for reporting this comment. Undo
edzard(3b Canada)

--excepting the ...
"Non-UV-treated polyethylene is both weakened and embrittled by UV radiation, and a nice cover of algae, koi and water lilies will slow, but not stop that. UV-treated HDPE should be fine"

Unfortunately I see unlined ponds quite often and the thoughtless results from this, --broiled fish and so forth, therefore & ergo,.. I can not imagine anyone leaving a pond unlined. Common sense and the mere-est grasp of the aesthetic would indicate that a pond should be lined with stone throughout...
therefore, by your observational note on the importance of UV treated HD plastics being 'fine'...
I should think a pond construction class to be quite informative... however,.. someone else can do it as I lack the time.

    Bookmark   September 28, 2004 at 7:49PM
Thank you for reporting this comment. Undo
Gorfram(7b W Oregon)


I bow to you twice.

First, that the lining you referred to is stone, and is needed to protect pond contents (is that because the thermal mass of the stone lining keeping it from heating & cooling rapidly?).

Second, I was too glib with my "should be fine". On *thinking* about it, I now remember that UV-protection in the HDPEs I have worked with will not do for sustained long-term exposure, only for comparatively shorter exposures during shipping, storage and installation.

I *hate* being wrong. (So you'd think I'd do it less often, wouldncha? :)

- Evelyn

    Bookmark   September 28, 2004 at 10:30PM
Thank you for reporting this comment. Undo

Thanks edzard for the information - I was not aware of the sandwiched geotextile products.

Evelyn, will you marry me! :D I'm not sure what I'll tell my wife but your witty humor is always a breath of fresh air!

jeepster - the powdered bentonite was exactly what I was questioning. Have you used it on smaller projects like stream beds?

JOJG has come down hard on the EPDM liners. While I certainly see the ease of use and cost benefits, they do make a good point. That point being that the liner will fail in 20-30 years and you will have to destroy the pond and the garden area around it to replace it. All at a time when the garden is maturing and hopefully looking its best.

What are your thoughts regarding this. Does that make the case for clay lined streams and ponds? Is a clay lined stream a better stream, in terms of plant ability, shoreline esthetics, etc?


    Bookmark   September 28, 2004 at 11:55PM
Thank you for reporting this comment. Undo
edzard(3b Canada)

EPDM liners are not the same as the HD plastics. EPDM tends to 'star' or fracture when impacted during stone installations. HD's will as well, except the size of stone would need to be about a ton and ahalf dropped from about 5 feet.. and then it might star, excepting that the HD is already highly compressed,- the chances of it being compromised are very very marginal. In fixing it, it becomes renewed, there is no patch, just a removal and a reseaming which is unified with the original body of the plastic.

The EPDM is fixable, however not seamed in, rather patched over, which will eventually give way due to ice expansion/contraction.

The Bentomax's as sandwiched bentonite, or even loose bentonite requires firstly a clay base with high saturation capability and must always be sandwiched with pressure or the weep rate changes.

ie: waterfalls comprised of only loose bentonite will erode when the jelly state is reached. Great if you can keep up to it yearly and have no fish, which will suffer from the platelets, recognising that a part of the composite is similar in size to diatomacious earth, yet in this case suffocating the fish restricting flow through the gills.

and Evelyn's accurate observation of the reason for stone lining is heat/cold retention = also vertical recirculation of water, yet much more as well. There is a layer of sand installed during the alignment (different techniques of interlocking for structure) of the stone that acts as a natural filter, growing medium for plant material (also can be a curse), acts as support layer for creating edging of your choice for aesthetics (bowls, edges, receptacles, pockets, peninsulas, refinement of shaping streams and 'oceans' with bays or supporting islands for bridges of whatever size or cape 'strewn stones'... the stone liner is the variable plant material of the usually 'laid in concrete' limitations that surpass the objectives of the JoJG concrete 'build it three times' necessity.

Here one may take the pond out, shrink it, expand it, reshape it, reset the stone, change the 'tension' of the garden, recline stones that require reclining with maturation of the garden, not to mention, lightweight as other medium that are not stone may also be used...

Simultaneously, currents are created within the pond that not only shape cold / warm channels to direct where fish will school, but also that the depth or absorption of waves creates the rippled effects [design tensions] of the surface water.
Directly this is what creates the 'meditative' quality of water, by rippling the surface which combines with a light source that effects the brain much as strobelighting can dis-orient the mind....
(emerging stones from water also redirect above water air flows, adding to the effects of ponds and how the plant movement responds with the visual environment.)
this liner captures the 'side of ocean' angle of incedence that provides the '7th large wave' effect of the real ocean in providing a 'sounding surface' much as waterfall tuning stones adjust treble and basso, these provide the treble 'slap - yiiisssssh' effect of receding waves...

for context, take a close look at the pond of Kinkakuji, (no it does not use a HDP liner) and ask if it is one flat surface or is there a landscape beneath***?... look for the wavelets or 'silver reflection' compared to darker placid water and the sense of oceanic depth of space that is created and compare notes on reef bio-mechanics.
(*** as a design sidebar, in one garden representative of the Tale of UrasenkeTaro we had placed a 6 piece lantern submerged in the water to light the unchanging timeless Realm of water as compared to the changing of the seasons above... as a stone contemplation garden replete with waterplants for shrubs, a night-lit step stone pathway sanzon garden within the pond, yet on the surface it was merely a 9" triangle stone sail of Taro's ship, yet also beneath the waves was the "old man that is Hong Kong")

and the average cost is about .66 (cents) a square foot compared to 1.35 for bentonite products compared to a higher figure for cement, or blown in cement.... with a longer life span in greater adversity,.. ground heaving freeze, etc.

Not to mention the obvious benefits of weight distribution, allowing a cattle drive to go through
---just a few side notes on pond construction...
and guess who does not endorse the use of this technology... ah well. Shrug, with Japanese gardens I've come to realise, never say never and always use what provides the design solution.

    Bookmark   September 29, 2004 at 1:58PM
Thank you for reporting this comment. Undo
Gorfram(7b W Oregon)

Thanks, Greg! A gal doesn't get an offer like that every day ;)
But I'm not sure what *I'd* say to your wife, either (or to my beloved BF :) maybe I should just wish your singular spouse the Very Best of Good Luck :)

Edzard, you are a continuing revelation. How could I not have realized, until you so fully illustrated it, that the reason an "empty" pond seems so lifeless under the surface is because it *is* lifeless under the surface?
From which it follows that a pond liner should support rocks, boulders, plants, plant & fish debris, islands, boulders, and the occasional cattle drive :)

From the Gorfram Gets Technical Dept:
(hitting Page Down key optional :)

EPDM is short for EPDM rubber, which is short for (synthetic) Ethylene-Propylene-Diene-Monomer Rubber, which you guys dont really need to know :) What may be useful to know is that is what is called "thermosetting", which means that is reacts to heat like an egg does: by setting into a structure that, although flexible, cannot be re-formed without destroying the molecular structure of the material.

HDPE is (as noted above) short for High Density PolyEthylene. This is what is called a "thermoplastic" material, which means that it reacts to heat much like metal does: it melts at high heat, is very formable at somewhat lower heats, and maintains a sturdy but somewhat elastic structure at normal atmospheric temperatures. (In theory at least) it could be melted and re-formed any number of times without harm to its molecular structure.

[Note that HDPE differs from most metals in that it is much more elastic at normal temps, and that its forming and melting temperatures are much lower. Building a bonfire in your newly drained HDPE pond liner to dry it out would be a Very Bad Idea.]

What this means is that, after your EPDM pond has been put to use as a traditional Japanese Moose Wallow, you can pay Edzard handsomely to come along and repair all the fractures and stars by gluing (with a pretty darned good glue, admittedly) EPDM patches over and in place of the damaged spots.

But, after my (purely hypothetical) HDPE pond has been put to use as a traditional Japanese Backhoe Wallow, I can (purely hypothetically) pay Edzard handsomely to come along and repair all the fractures and stars by melting and reforming the molecular structure of the HDPE itself, such that (at least in theory) I would not be able to tell under a microscope which was factory-formed material and which was field-repaired.

And the HDPE is stronger to start with.

The final argument against EPDM (for this post, anyway :), I borrow from Beverly Nichols, the very non-technical, very non-Japanese, garden writer; who wrote that he could not see a rubber lining laid into a pond without being reminded of old mens saggy long underwear.

:) Evelyn

    Bookmark   September 29, 2004 at 5:02PM
Thank you for reporting this comment. Undo
LouisWilliam(Z5 MA)

Wonderful primer in thermoplastics vs reaction cured cross linked polymers Evelyn. This all seems to miss the chance to provide some practical advice however. Yes HDPE is used widely for large scale projects. The reason is isn't used by homeowners or small gardens is that it takes special (expensive) equipment to carefully melt and reseal the seams used to join small pieces into big ponds. HDPE is the same "visqueen" material that is widely used for everything from throw away dropcloths to shipping bags. When thick enough (and High Density enough) to act as a geotextile material, it gets stiff, hard to handle and hard to seam. And you won't find it at the Home Depot. So if you are Rowdy Yates and have a back 40 to work with, good luck. If you are building a pond that big and looking for advice on the internet, you will need some luck.

EPDM is widely used by homeowners and small commercial installations because it works well and is widely available. It is made for the commercial roofing industry and works great (for 20 or 30 years, even in direct sunlight). They leave out the biocide used in roofing to kill moss (who would want to do such a thing?) and sell it as pond liner. It works because it is saggy and conforms well to uneven bottoms, just like that underwear. It is also available in wide widths and can be glued by an average homeowner with nothing more than his glue tube. Not the premium choice, but hands down the most popular. Go to the Ponds forum and see how many people use it - nearly all.

The problem with any liner is achieving a satisfactory slope to the pond walls. Pond people, and Japanese Garden Pond people are included, hate losing fish to predators, and the best deterrent is steep slopes to the sides. Not easy with liners. And nobody wants any liner showing above the waterline, but without good design and engineering, it usually happens. I have seen a lot of liner showing at public and private water features that spent a lot of money on water recirculation and filtration etc. but didn't get the basics covered. The liner has to be buried well below the dirt, rocks and other edging. Easy to damage any liner if you don't know what you are doing, so many ponds have a sort of gravelly slope that tries to hide the liner. Not very attractive.

If you have enough water or course, it doesn't matter much what your pond is lined with. This is the Kyoto approach, limited nowadays by constraints on those endless supplies of clean water. Bentonite falls in the middle ground - not really a waterproof membrane, but it can slow down the leakage rate to an acceptable level if applied and maintained correctly. First you start with a sheepsfoot roller... (Evelyn's clue to ask why you would roll their little feet)

I agree with Edzard's comments on bentonite and moving water - just the wrong application. If you have an acre of pond bottom and clay soil, get some local help and give it a try, but it isn't good for streams.

There must be a reason the majority of good JG's in the US and Japan use cement where they don't have a natural water body. It does work, isn't all that difficult to design, can be fixed, and lasts a long time if built well. Plenty of house foundations are expected to last a hundred years. and they see freezing cycles on the outside and heat inside - worse than many ponds. It just seems like a big undertaking for most people, and is admittedly too expensive for really big projects. And you are much more likely to get a natural looking edge if you build in a rock shelf with reinforced concrete. Of course you can also have a gradual slope and a pebble beach, but they usuall end up being raccoon and heron dining rooms.

Another key issue with liners, natural ponds, and cement is the whole water treatment/filtration question. Acre plus ponds can become naturalized with a low fish load and a high tolerance for turbidity. Everybody else needs some water treatment, and with koi that means bottom drains and skimmers. No way around it, and it adds another challenge to both liners and cement.

There is one other alternative. If you have a very loose grasp of appropriate priorities, you can find a natural canyon (courtesy of the Wisconsin glaciation) in impervious granite bedrock, excavate everything that doesn't look like a pond and fill it. Good luck to all with your water features.

    Bookmark   September 29, 2004 at 7:14PM
Thank you for reporting this comment. Undo


I have used a lot powdered bentonite. I use animal feed grade because it is easy to get @ my local ag center - comes in 80lb bags. I have heard of a well grouting grade that supposedly has a finer particle size but can not confirm. I can not afford liners.

Bentonite is an inert clay and will turn to jelly as it obsorbs water so it must be secured in place. I personally would not use it in dinamic situations of running water. Local clay in iteslf is a the cheapest and best product in my mind. I use bentonite because the clay in my pond is too porous. I have a 2/3 ac farm/fishing pond that I am incorporating into a "Japanese inspired" setting.

It should work great in a small pond because you can control it better. I would use it as an underlayment, as a sealant under other materials as it neadds protection or incorporate right into your pond soil. Your local extension office should have pond / bentonite literature avail for larger applications that will guide you in it's use.


Whay do you say that all ponds should be lined? A well constructed clay pond hear in Missouri will only drop about a foot in mid summer drought and that is due mostly to evaporation?

    Bookmark   October 1, 2004 at 7:27AM
Thank you for reporting this comment. Undo

Hi Everyone!

Sorry for the late post. I have an excuse but it is not a good one. Anyway I just wanted to say thanks to Edzard, Jeepster, Evelyn and LouisWilliam for taking time to respond and share their experiences. My two primary reasons for wanting to use bentonite was to; 1) not have to resort to concrete and, 2) to allow for a more 'plantable' edge so I could avoid long strings of rocks that look as natural as a paved highway. I have not decided whether to do the project or not. The stream as planned would be about 150 feet long. I'll probably change my mind a dozen times over the course of winter months. :D

Thanks again!

    Bookmark   October 7, 2004 at 10:48PM
Thank you for reporting this comment. Undo

Hey all!

We have a 2/3 acre pond for recreation. It leaks and the water surface always returns to the same level. It is about four vertical feet below optimum.

1.) Is there a way to determine exactly where the leak is?

2.) Assuming there isn't, should we go with a liner and then place stone on it? Bentonite isn't practical because I cannot safely work it into the bank soil.


    Bookmark   August 17, 2005 at 10:49AM
Thank you for reporting this comment. Undo
edzard(3b Canada)

your questions would be answerable if
1) you mention where you are, how cold, how warm it gets, mean averages.
2) type of soil you are in,
3) is there a current containment field? cement?, liner, clay?
4) the above post refers to sandwiched bentonite, which would not be useable if the weep rate was too high, due to ie: wrong base soil type, not being clay. How is it not possible to 'safely work it into the bank soil'?
5) if recreational, then what use does it undergo? is it country or city? is it exposed to wildlife? or pointed objects? does it have fish? is it a dugout? a natural basin?
6) what means of filling the pond is there?

Normally the leak is where the surface of the water returns to, somewhere around that perimeter, -if there is a containment field (liner),
-if there is no liner then that is the watertable.
-- as you can tell, I'm unclear how this pond is currently constructed.

    Bookmark   August 17, 2005 at 3:09PM
Thank you for reporting this comment. Undo
stittman(z7 CA)

I put in a plastic liner pond a few years ago. I guess it was OK until the bottom started getting gunked up and I tried to clean it. An impossible mess! I kept slipping and finding myself butt down in mud and goldfish excrement. The ugly thing sat there dry all last year, looking like a dead animal. This year I am going to rip all the plastic out and fill in the hole. That's about enough water gardening for me.

    Bookmark   January 15, 2006 at 8:46PM
Thank you for reporting this comment. Undo

Whew, sure has been a lot more info there than I can assimilate....I just need to know if plastic, rubber, tar paper, tile mastic, concrete or what would be "best" for my stream's liner. It's only about 12" wide, and falls about 16" over 75'. Plan to use river rock to line the edges and bottom.
BTW, I used waterproof thinset for filling in around rocks in the bottom of the upper 'waterfall' pond (about 5-6 feet accross) and a kingsize waterbed matress for my lower pond(about 6x4'). Large rocks and dirt hold the plastic covered cardboard edges, and it has a nice blue color.

    Bookmark   February 2, 2006 at 6:59AM
Thank you for reporting this comment. Undo
yama(7b Ga)

Hi All
It is nice to see/read peoples I know for a while, specialy Evelyn . Since Edzard and others provideing good, usefull information,I have not much to write. I am so happy to see Evelyn's name here. If you have Cady's email address Please contact to her.Cady is happy to hear from you. We are worry about you. I havn't talk to Edzard over telephone yet. I miss lots of GW freinds.
Cady and I thinking to write a book togather. we will be busy for a while.
I am so happy that you sound doing well................mike

    Bookmark   February 11, 2006 at 11:30PM
Thank you for reporting this comment. Undo

I am building 100x65 pond and lining it with edpm . Is there any product to cover liner with to protect from deer getting into water? Thanks

    Bookmark   June 24, 2009 at 12:19AM
Sign Up to comment
More Discussions
transplanting an older tree in the Summer
I have a 10 year old Japanese maple tree that is in...
Dwarf Japanese Maple Damage from snow
We just had a severe snow event last week (5 1/2 ft)...
I built a Japanese Torii for my garden.
Canadian west coast winter
Not a desirable state for a layout aspiring to look...
e-1 size
Can you keep a j m emperor 1 at 8 to 10 feet when they...
© 2015 Houzz Inc. Houzz® The new way to design your home™