When planning a backyard or farm pond, one question that may arise is if you can use a tarp instead of a commercial pond liner. Tarps are inexpensive, easy to find, and seemingly waterproof—so at first glance, they seem like a practical choice. However, while a tarp may work for a temporary or experimental pond, it rarely performs well as a long-term solution. Understanding the differences between tarps and true pond liners can save you time, money, and frustration in the long run.
What Are Tarps Made Of?
Tarps, or tarpaulins, are usually made from either polyethylene (PE) or polyvinyl chloride (PVC).
Polyethylene tarps are lightweight and widely used for temporary weather protection—covering firewood, shielding vehicles, or acting as makeshift roofs during construction. These are the familiar “blue tarps” seen at most hardware stores.
PVC, or vinyl tarps, are generally thicker and more durable. They’re often used in applications where more abrasion resistance is needed, such as trucking, industrial storage, or marine use. Both kinds are reinforced with woven scrim to add strength, and they may have coatings that help with water resistance. However, the fact that tarps are waterproof to some degree doesn’t mean they’re suitable for long-term submersion or pond use. Their intended purpose is to repel rainwater, not contain thousands of gallons of water under constant hydrostatic pressure.
Why Don’t Tarps Make Ideal Pond Liners?
Although tarps can hold water temporarily, they fall short in several key areas when compared to purpose-built pond liners.
Thickness and durability: Most standard tarps range from just 4 to 8 mils thick. By contrast, a liner designed for long-term pond use is typically 20 mils or more. That extra thickness makes all the difference. A thin tarp is easily punctured or abraded by rocks, roots, or even the pressure of the water itself. Once torn, repairs can be difficult, and leaks are almost inevitable.
UV resistance: Even if a tarp survives the initial installation, it won’t last long under sunlight. Most consumer tarps offer minimal UV protection, and constant exposure to the sun causes the plastic to become brittle and crack. Within a single season, the surface may start to flake or degrade, creating leaks and contaminating the water.
Seams and waterproofing: Many tarps have seams that are heat-welded or stitched but not designed to be watertight under pressure. Water can slowly seep through these weak points, undermining your pond’s integrity.
Chemical safety: PVC tarps, in particular, can pose risks for fish and other aquatic life. The flexible plasticizers used in their manufacture can leach out over time, introducing toxins into the water. These compounds may not be a concern for short-term use but are unsafe for ecosystems that include fish, frogs, or plants. In short, a tarp might work for a child’s wading pool or a temporary decorative pond, but it’s not a reliable or environmentally sound choice for a permanent water feature.
Why Are Geomembrane Liners a Better Choice?
Modern geomembrane liners are specifically engineered to create an impermeable, long-lasting barrier between the soil and the water. They’re used not just in ponds but also in landfills, reservoirs, and industrial containment systems where leaks would have serious consequences.
The three most common materials used for pond liners today are Reinforced Polypropylene (RPP), High-Density Polyethylene (HDPE), and Reinforced Polyethylene (RPE).
RPP liners offer a balance of strength, flexibility, and chemical resistance. They can conform easily to irregular pond shapes, resist punctures, and endure decades of exposure without breaking down. They’re also considered safe for fish and plants.
HDPE liners are extremely tough and are used in demanding environments such as mining and waste management. While they’re less flexible and more difficult to install in smaller ponds, they’re virtually impervious to chemicals and UV degradation. With professional installation, an HDPE liner can last 20 years or more.
RPE liners combine many of the advantages of both RPP and HDPE. They’re lighter and easier to handle, yet still remarkably strong and tear-resistant. Because RPE liners expand and contract very little with temperature changes, they’re less likely to develop leaks over time. Another major advantage of geomembrane liners is that they can be custom fabricated to match your pond’s exact dimensions. This minimizes seams, ensures a snug fit, and greatly reduces the risk of leaks. Most importantly, these liners are fish-safe, meaning they won’t release harmful chemicals into the water.
Doing It Right the First Time
Choosing the right liner from the start can determine whether your pond becomes a source of pride or a constant maintenance headache. While tarps may seem like a cost-saving shortcut, they’re best suited for temporary or experimental ponds, not for a structure you expect to last years.
A proper geomembrane liner, made of RPP, HDPE, or RPE, represents an investment in longevity. It will stand up to sunlight, resist punctures, and maintain its waterproof integrity season after season. In the long term, the small savings of using a tarp are quickly lost to the cost and effort of constant repairs or replacement.
Building a pond is more than digging a hole and filling it with water. It’s about creating a lasting ecosystem. For that, you need materials designed to last. Investing in a high-quality pond liner ensures your pond stays clear, safe, and beautiful for decades to come.
