BENTONITE CLAY POND LINERS VS. TRADITIONAL LINERS

We receive numerous inquiries from customers about bentonite clay pond liners and how they compare to traditional passive liners such as our Premium RPE liner. Bentonite represents a distinct method of achieving a watertight seal compared to passive liners, and like any product, it has its advantages and disadvantages.

PASSIVE VS ACTIVE LINERS

The first aspect to understand when comparing bentonite to materials like RPE is the difference between an active and a passive liner. A bentonite clay pond liner is an example of an active liner. It's termed 'active' because it requires an active mechanical/chemical process to become waterproof. By itself, bentonite is just a clay and not waterproof. However, when it becomes wet, it expands many times its weight, absorbing water. If constrained, it can form a watertight compressive seal.

On the other hand, a passive liner, like our RPE liners, does not depend on an 'activation' process to function. These liners are inherently watertight and provide immediate results when laid down.

bentonite

Raw bentonite clay

Our Favorite Passive Liners

ADVANTAGES OF BENTONITE

The most significant advantage of bentonite, from a marketing perspective, is its theoretical ability to self-heal and expand around punctures when installed correctly. For instance, if you were to line a pond excavation with a layer of bentonite clay, it would be possible to drive elements like dock piles or pipes through the clay, or even operate heavy machinery over it, and subsequently repair any damage by simply adding more clay. Upon contact with water, bentonite is designed to expand and self-seal any penetrations up to a certain extent. However, it's important to note that this self-healing property has its limits. If a hole or penetration is too large, the clay may not be able to expand sufficiently to seal it effectively.

DISADVANTAGES OF BENTONITE CLAY POND LINER

We frequently receive phone calls from customers seeking to replace a leaking bentonite clay pond liner with an RPE liner, often due to improper installation. A common mistake is mixing bentonite clay with existing soil to reduce costs. If this mix is too thin, or not spread evenly, it can lead to leaks. Even a single thin spot, or an area accidentally scuffed and left without clay, can cause leakage. Once these leaks occur, they are notoriously difficult to locate and repair. Many customers, after years of attempting to fix their leaking pond, eventually opt for a more reliable passive liner like our Premium RPE liner.

Another major disadvantage, in our view, is the method of using loose bentonite clay, which we believe is inadequate for ensuring a 100% watertight seal. To address this, some companies produce manufactured bentonite liners, typically consisting of a layer of bentonite clay sandwiched between two layers of geotextile fabric. This design helps to keep the bentonite in place, providing a uniform layer over the excavation. However, for these liners to be effective, they must be properly confined. Bentonite works by expanding to fill a void, forming a compressive seal that stops water flow. If the bentonite can expand without constraint, it will not form this seal and won't be entirely watertight. Therefore, we recommend adding a substantial amount of soil or other material over a manufactured bentonite liner to provide the necessary confining weight. Without this weight, bentonite liners may not function optimally and could fail.

ADVANTAGES AND DISADVANTAGES OF PASSIVE LINERS

The great advantage of passive liners, like our Premium RPE liners, is their immediate functionality. Simply unroll them, and you have a watertight pond ready to go. The primary disadvantage of passive liners compared to bentonite is their inability to self-heal when punctured. However, in practical terms, this often isn't a major issue. Small punctures that may occur during installation can be easily repaired by heat welding patches onto the RPE liner. For mission-critical applications, a 'belt and suspenders' approach can be employed by installing two separate liners, with the second serving as a backup in case the first one is punctured.

COST

Initially, people might assume bentonite is more cost-effective, especially when considering the price of a truckload (or multiple truckloads) of raw bentonite clay, particularly for those living near Wyoming where it is mined. Many attempt to reduce costs by mixing bentonite with native soil. However, as mentioned earlier, using raw clay can be problematic, and mixing it with native soil introduces uncertainties regarding the correct clay-to-soil ratio. Consequently, most people end up opting for a manufactured bentonite clay pond liner, which usually turns out to be more expensive than passive liners like RPE. Therefore, cost alone is not always a justifiable reason to choose bentonite.

Ultimately, our preferred choice for pond lining is Premium RPE liner. It's strong, lightweight, UV resistant and can be customized to virtually any size required for your project. If you have any questions about pond liners, or would like to discuss your specific project, please don’t hesitate to contact us!

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Bentonite Clay Pond Liners vs. Traditional Liners

We get quite a few calls from customers asking about bentonite clay pond liners and how they stack up to traditional passive liners like RPE (reinforced polyethylene), and EPDM rubber. Bentonite is a very different means of achieving a water-tight seal compared to a passive liner, but like anything it has it’s advantages and disadvantages.

Bentonite Clay Pond Liners
Raw bentonite clay

Passive vs Active Liners

The first thing to understand when comparing bentonite to something like RPE is the difference between an active and a passive liner. A bentonite clay pond liner would be an example of an active liner. It’s called active because there’s actually an active mechanical/chemical process that must take place before the material becomes waterproof. On it’s own bentonite is just a clay and is not waterproof. However, when it gets wet, it expands many times it’s weight, absorbing water. If it has something to expand against, it can form a water-tight compressive seal and become water-tight.

In contrast, a passive liner does not rely on any ‘activation’ process to work. For example, our RPE liners are simply water-tight liners that you lay down and get instant results.

Advantages of Bentonite

The biggest advantage of bentonite from a marketing point of view is theoretically it can self-heal and expand around punctures if it’s installed correctly. For example if you were to line a pond excavation with a layer of bentonite clay. You could drive penetrations through the clay, or drive a piece of heavy machinery over top, and easily fix any damage after the fact by sprinkling down some more clay. When water is added, bentonite is designed to expand and self-heal any penetrations TO A POINT. Obviously if the hole or penetration is too large, you will be out of luck as it can only expand so much.

Disadvantages of Bentonite clay pond liner

We get quite a few phone calls from customers looking to replace a leaking bentonite clay pond liner with an RPE liner. The reason for this is usually improper installation. Often times people will mix bentonite clay with the existing soil to save on material costs. If this mix is created too thin, the pond will leak. If the mix isn’t spread out perfectly even, the pond will leak. If there’s even one single thin spot, or a spot that was ‘scuffed up’ leaving a small area with no clay, the pond will leak.

Another big disadvantage in our opinion is the methodology itself of using loose clay. Loose bentonite clay in our opinion is a bad idea if you’re looking for a 100% water-tight seal. To fix this, there are certain companies out there that make manufactured bentonite liners. By manufactured, we mean there is often a layer of bentonite clay sandwiched between two layers of geotextile fabric. This helps ‘confine’ the benotinte somewhat so that it can’t migrate away easily, leaving a uniform layer over the excavation. However, for this to work properly, you really need to confine the liner. The way that bentonite works is that it expands until it fills a void. At that point, it forms a compressive seal and stops all water from flowing through. If the bentonite is allowed to expand indefinitely without something to confine and stop it, it will NOT form a compressive seal, and it won’t be 100% water tight. That is why we would recommend bringing in a good amount of soil or other material over top of a manufactured bentonite liner to provide some confining weight. Without this weight, benotnite liners don’t seem to work well.

Advantages and Disadvantages of Passive Liners

The nice things about passive liners, like our Premium Grade RPE liners is that they work right out of the box. Just unroll them and immediately you have a water-tight pond. The only real disadvantage of passive liners compared to bentonite is that they cannot self-heal if punctured. However, in practice we usually don’t find this a not a huge issue as you can easily heat weld patches onto RPE liner to repair any small punctures if an accident happens during installation.

Cost

In the beginning people can tend to believe that bentonite is cheaper if just looking at the cost of a truck load (or multiple truckloads) of raw benonite clay. However as we explained above, using the raw clay can be asking for trouble in our opinion. So in the end, most people will go with a manufactured bentonite clay pond liner, which is usually more expensive than a passive liner like RPE. So cost alone isn’t a reason to use bentonite in most cases.

In the end, you may already have guessed what we like to use to line a pond: RPE. It’s strong, light and we can make it in just about any size you need for your project. If you have any questions about liners, or would like to discus your particular project, please give us a call!

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