Kloubec Koi Farm

Is that a Pontiac Fiero in your Pond?

Polyurea Coating for Pond Construction

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What’s all this buzz about high-tech coatings and lining systems for ponds? Over the last decade, we’ve been hearing more and more about this technology. It’s called polyurea, and no, it is not a medical ailment. What it is, is a spray applied polymer that’s used to create rugged, long lasting lining systems for water features.

As I write this article, I’m sitting at a picnic table, lakeside, at my in-laws’ summer cottage in Connecticut. As I look at the lake, I take from it what I most enjoy, the movement of the water, the smell of the air, the occasional fish that swims by the dock. Bodies of water are enjoyable, especially for those who choose to create their own water features to enjoy their own fish. It is reasonable to believe that someone who has been involved in the hobby of maintaining a pond for show fish, such as koi, or their prized water lilies, has probably run across problems with their pond or ponds at some point.

One of the most dreaded and stressful problems one can experience is a pond that leaks. Leaks are caused by any number of reasons. But as I enjoy this lake, I don’t have to worry about it leaking. I don’t have to worry if there’s enough water for the fish and the plant life that thrive in it. I have noticed that pond keepers often spend just as much time worrying about their ponds as they do enjoying them. Wouldn’t it be nice if our ponds gave us the peace of mind the lake offers? That is a notion I have taken to heart. That is why I spray polyurea ponds.

Shotcrete shell prior to installation
Shotcrete shell prior to installation

A quick mention of polyurea’s history reveals that it is relied upon for much more than creating a habitat for aquatic life. It has been used extensively in the industrial sector for projects such as the coating and protecting of concrete, steel structures, and for purposes like the containment of wastewater at sewage treatment plants. I’m often asked, isn’t that stuff also used for spray on truck bedliners? Yes, that is a common use for polyurea technology as well. But it has also been used on high profile jobs such as the San Mateo Bridge, the Boston Tunnel, the Pentagon shipping and receiving facility’s subterranean roof, as well as both Yankee and Shea Stadium in New York. Do you remember the Pontiac Fiero? Well if you owned one, you had a car that was one of the first to have polyurea parts such as bumpers, dashboards and armrests. Its versatility pretty much limits its use to that of our imaginations.

Shotcrete shell after installation
Shotcrete shell after installation

So what makes polyurea so special? A few characteristics stand out. Polyurea systems have the ability to dry, or as the industry says, “gel,” in mere seconds. Polyurea systems also produce very strong physical properties when compared to other conventional coatings. These attributes enable a trained applicator to fabricate a custom lining system that will be ready for use in a matter of hours, without having to wait days for it to cure like conventional coatings technology. Another important key to understanding the unique quality of polyurea is its independence when used in a water feature. Conventional coatings are typically thin, an example would be 20 mils, or 20 thousandths of an inch. Polyurea systems are “thick film” systems. They can be sprayed with an unlimited thickness, which would typically range between 125 to 250 mils. That’s an eighth to a quarter of an inch thick! Because of its thickness, even though it is a coating, what we really see in these water features is actually a lining system that can function independent of the surface it is applied to. Coatings such as epoxies or urethanes require application to a structural surface such as concrete. They depend on adhesion to the surface, which is a common cause of failure when the coating delaminates and is breached. If the concrete cracks, the crack may transmit through the coating, causing a leak. These are not issues with regard to polyurea.

Pond with gunite shell before application
Pond with gunite shell before application

The other benefits of polyurea we should know about have to do with the functionality of the pond. First off, the term polyurea is a description of a type of coating, or technology with regard to how the coating cures. What this means is that there are many types of polyurea systems in existence, just as there are many types of epoxies or polyurethane coatings. Therefore, certain polyurea formulations are ideal for use as a lining system, whereas some may not exhibit the properties we look for when doing this type of installation. But in theory, they all cure in the same manner. Polyurea coatings for these types of applications are what we call elastomers. Elastomeric coatings exhibit just what the term implies, elasticity. The ability of a polyurea system to stretch under great pressure is what sets it apart from all other coatings, and it’s this property that makes it ideal for water features.

Sean Boeger applying the lining system
Sean Boeger applying the lining system

When we speak of the strength of a polyurea system’s elasticity, two properties we look at are the formulation’s tensile strength and elongation. Tensile strength is the measure of force required to rupture or break the coating when it is stretched. Elongation is directly related to tensile strength and represents how much the coating will physically stretch before it meets the maximum tensile strength and ruptures. Successful polyurea applications for water features have been found to have tensile strength ratings in excess of 2,000 psi (pounds per square inch) and elongation ratings in excess of 500%. Now you may be saying, what the heck does this mean? In essence it means that a coating with these properties can stretch five times its length before breaking, and it would require over 2,000 pounds of pressure per square inch placed on the coating to do so. Even better is that a typical polyurea formulation will maintain these properties through a temperature range of -40°F to 350°F! This why polyurea is so strong and puncture resistant. I tell people they can walk around in their polyurea ponds with golf cleats on if they want. Try doing that with a rubber liner. Another common question I’m asked is will it crack? No. And now you know why. The right polyurea formulation is well suited for the stresses and pressures created by large masses of water as well as large decorative boulders. We have often seen boulders the size of small imported cars being dragged into place on top of polyurea lined shelves without detriment.

Pond after polyurea/geotextile fabric installation
Pond after polyurea/geotextile fabric installation

Besides its strength and flexibility, there are other advantages polyurea offers with regard to incorporating the common plumbed fixtures we find in most ponds. Seals made to piped returns, skimmers and bottom drains are usually done by means of adhesive sealants, bolted on flanges or clamps. These transitions to a pond’s filtration system are a common source of leaks if improperly installed or in the case of a liner pond, if they tear free of the fixture due to movement. Polyurea definitely offers improvements over these conventional methods. The usual means of clamping a lining system around piped returns to create a seal is still done in the same way. However, because polyurea is sprayed, sound material that is sprayed around a pipe can be clamped after it initially gels, and then sprayed again, encapsulating the clamp. This creates a situation where the clamp can never corrode because it will never be exposed to oxygen or the water, let alone become loose. Skimmer faces can be encapsulated as well. The polyurea around the skimmer face can then be chemically bonded back to the rest of the lining system prior to the faceplate being bolted on. This offers an additional seal between the lining system and skimmer through the mechanical bond of the coating. This is better than solely relying on the pressure between the liner and skimmer face to create the seal. If bottom drains are not set in concrete, they can be entirely encapsulated as well. Again, the polyurea around the drain can be chemically bonded back to the rest of the lining system. If the drain is seated in concrete, polyurea is only sprayed down into the drain to an appropriate thickness. The rigidity of the polyurea keeps it seated and sealed within the drain. In either situation, the typical flange that is used to create the mechanical seal to the drain is no longer needed, once again eliminating the potential for leaks.

As for the general application of a polyurea lining system, it can be installed over an earthen excavation or a concrete shell. A common component used in constructing a polyurea lining system is geotextile fabric. There are many types of geotextile fabrics, but data has shown that fabrics made of a woven polypropylene incorporating perpendicular fibrillated and monofilament strands work best. It is important that your polyurea contractor has an understanding of this, and uses the proper fabric. The wrong fabric can cause inherent weaknesses in the lining system. Segments of fabric are sprayed, ensuring uniform thickness of the polyurea that is free of voids. Sprayed segments can be conformed to the shape of the pond. As the segments overlap, they are seamed with more polyurea until the seam is flush with the rest of the lining. What is achieved in the end is actually a seamless lining system that is one complete molecular chain. There are no seams, and therefore, there can be no seam failures. Application to structural shells can be done with the use of geotextile if they are particularly rough or there is concern that they will experience significant cracking. Otherwise, structural shells with a properly prepared surface can be sprayed directly.

There are other questions I commonly hear. Can it be sprayed over an existing liner? I don’t recommend it. It can interfere with conforming the new lining system, plus it is good for the applicator to see if a problem may exist with something under the old liner. Can it be sprayed directly to dirt? No. Now I know some people out there may have heard that this is possible, but I would venture to say that it is not a good idea to spray something that heats up to over 200°F onto something with a lot of moisture content such as dirt. Can you say pinholes? Is it bear proof? Yes, I said bear proof. One koi hobbyist had an issue with bears clawing at her fish as they escaped to the bottom of the pond. And yes it is bear proof. It’s moose proof too, but that’s another story. How long does it last? The technology is only twenty years old, but data from the lab shows longevity in excess of seventy-five years. There just isn’t any seventy-five year old liners to hang our hat’s on yet. Here’s an important one. Can I do it myself? Absolutely not. Proper application of polyurea for water features requires special equipment and training. There are do it yourself cartridges that can be sprayed with low pressure. However, once these cartridges are spraying, you can’t turn them off until they are empty or they will clog. The limits of this type of equipment would make seaming and incorporation of plumbed fixtures all but impossible. Another important thing to consider is safety. The raw materials that comprise polyurea contain isocyantes, which while airborne during spraying, constitute a respiratory hazard. Proper safety equipment is required during spraying. Some things are best left to the professionals.

Author Sean Boeger
Author Sean Boeger

So in looking at the overall picture, polyurea offers superior strength and security over conventional methods. Does it have any downside? Yes, the price. Polyurea is probably the most expensive means to ensure your pond holds water. Depending on difficulty and quantity of installation, pricing ranges from $8.00 to $12.00 per square foot installed, with $10.00 being the norm. The raw materials are petroleum based, which contributes to the cost. Yes, it is very expensive, but most pond owners that choose polyurea do so because they have already experienced the inherent problems associated with the conventional methods and they do not want to deal with the headaches. With all the money we invest for proper filtration, equipment, care of plants and fish, the fish themselves and the labor that goes with it, the question we need to ask ourselves is how much will it cost to build your pond the wrong way? Polyurea offers the last lining system you will ever need that actually allows enjoyment of your pond, with peace of mind.

About the Author

Sean Boeger is the owner of Poly-Pro Industrial Coatings and the developer of the Infinity Water Garden and Koi Containment polyurea lining system. Sean has been working in the polyurea industry for the last eight years. He is heavily involved in the Polyurea Development Association, which is an international trade association for the promotion and education of polyurea technology. Sean is an instructor with the PDA, as well as chairman of the organization’s Training Committee. He has also sat on the PDA board of directors for the last three years. Sean can be reached at 203/961-9888.

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