Its been many years since I started working in the pond industry. Many things have been learned and expanded upon, making this market a fast growing, money making, and fun part of doing a landscape project.
No matter how much we learn and expand our knowledge about constructing ponds, there is one basic area that people stress over -- it's holding the water in the pond without leaks.
Yes, we can dig the hole in the proper location, and maintain it once the pond is installed. But it's the lining portion that so many worry about, especially if the pond is large and requires a larger membrane to line it.
I hear so many different questions when it comes to lining a pond: "Can we just pour the liner in place?" "Does it have to have seams?" "Do I have to line it?" "What happens if I use one material over another?"
Why has keeping the water in the pond become such an issue? I am hopeful that the reason this is a concern is because water is our most valuable resource, which we cannot afford to waste.
Are you one of those who falls into the category of worrying about the liner, making sure it doesn't leak? If you are, then you're in luck; it truly is not that hard. With a small amount of effort, you can line your pond and have a beautiful, natural-looking water garden for everyone to enjoy for years to come.
Now the question is, what materials to use in lining the pond? Some believe concrete to be the material of choice, others prefer a mixture of concrete and a membrane, while others prefer just a membrane to keep the water in. My choice is the latter; I personally feel that concrete is a waste of time and money when it comes to lining a pond. It is unnatural looking and prone to a variety of problems, such as leaks and water quality. I have not yet run across a pond made of concrete that has not leaked. I don't care what market you're, in time that concrete is going to crack. In some areas it only takes months, while in others it can take a few years. No matter what, they all eventually leak. (I am not talking about a pool.)
A concrete-lined pond with a membrane underneath is another solution that is popular with many contractors. They now know that a concrete pond will leak, so they place a membrane underneath. Although this is a solution that can help, it may not prevent the leaks. Many will use an inexpensive membrane that doesn't move or stretch when the concrete expands and contracts and, in time, the membrane itself will crack, causing a leak.
If you happen to be in the mindset of using concrete on top of a membrane, I would strongly recommend a membrane that will expand and contract with the concrete and not tear. I have found that rubber membranes are the best for this purpose. Most of the known rubber membranes in the pond industry have the ability to stretch up to 300% before they begin to tear. This is a considerable amount of expansion, more than concrete will ever do, unless you have a major earth moving event, such as an earthquake.
My choice for any pond of any size in any application, especially when you are trying to achieve a natural look, is to go with only a membrane. However, not all membranes are created equal. Yes some cost more money than others, but you do get what you pay for. I prefer a rubber membrane because of its sun resistance, elongation, and ease of installation. Some membranes do not do well in the sun; the UVs literally eat away at the membrane and they become brittle and crack. These membranes are difficult to install, seam and repair later on as they change their make-up and become a different material once the sun begins to attack. For these reasons, the industry has chosen to go with rubber membranes.
So you happen to be a contractor who usually chooses a rubber membrane, but you decide to go with another membrane when it comes to larger projects. I always find this interesting; when I ask "Why?," the answer is usually that the other membranes do not have any seams. This is not so; the only membrane from a pond manufacturer that is produced in large panel sizes is made of rubber. The largest factory-seamed panel of rubber is 50' x 200', with common sizes being 50' x 100' and smaller. The other membranes come from the factory at a maximum width of either 10' or 12'; they are sent to fabricators who must seam the panels together and than ship them to the project. So, if you believe membranes other than rubber are made larger, you have now been informed that this is incorrect.
Contractors are generally fearful of seaming membranes in the field. This process is actually quite simple. It is a matter of keeping a clean and dry membrane, and following the instructions of the manufacturer. I personally have been involved with well over 3,000 lineal feet of seaming of a rubber membrane without any leaks. A little trick to making sure your seams are not going to leak: take a small air compressor with 75psi and run the air along the seam to test for any leaks. If you find one, repair it on the spot. After this, you can add water immediately.
So for all of the reasons mentioned, when choosing a liner for a pond, think rubber.