Preventing Seepage in a Catch Basin

Catch basins are prone to the water loss known as seepage just like many concrete lined water features. Seepage is the term used for water that escapes downward, due to gravity, through tiny gaps between soil particles or other materials. A material’s ability to block this flow is known as impermeability. Many materials used for construction catch basins are less impermeable than you might assume. Yet flexible liners are highly impermeable, effectively ending the seepage loss problem when installed properly in a storm drain system. Make sure you choose the right options for controlling seepage in your catch basins.

Why is Seepage a Problem?

A little water leaking through concrete or soil may not sound like a big deal if you’re new to seepage. However, it’s a more destructive force than you might think. Wet soil is prone to movement, and moving water is particularly likely to expand and cause slides or collapse. When water constantly leaks from an unlined concrete catch basin, the soil around it becomes destabilized. The basin itself may shift, drop, or collapse due to the changing pressures or levels of support. Some water that escapes through seepage is also lost if it doesn’t return to a natural water table or aquifer. If it does reach the water table, it may still carry contaminants if there’s only a few inches of soil above the table. This doesn’t provide adequate filtration for groundwater recharge. Finally, rapid seepage can flood surrounding areas by forcing water to the surface of the soil. Catch basins work better when they hold water as intended. If the slow release of storm water is desired, other features like dry wells are a much better option.

Issues with Concrete

It’s a common misconception that a precast catch basin will withstand the pressure of the soil around it and avoid cracking for years to come. Many concrete basins are cracked during installation or in the years of use following. Hairline cracks form that are nearly invisible to the eye, but water has no problem seeping through the space. The concrete material itself is also porous. There are tiny openings in the surface that create capillary action like a sponge. This can suck water into the catch basin from saturated surrounding soil or release it through seepage. Many catch basins are lined with some kind of roll or spray on sealant to avoid this problem. Unfortunately, these sealants also crack over time in ways that are hard to spot. Flexible liners, particularly those made with multi-layered RPE like ArmorPro, will provide the best protection against seepage when paired with concrete catch basin structures.

Sealant Struggles

Silicone and epoxy-based sealant products are often marketed as an easy solution for sealing leaking or cracked concrete catch basins. They’re also recommended for application before installation to cover the porosity of the bare concrete. Unfortunately, these liquid products are not as easy to use as they appear. Getting a thick and even enough application over every inch of the catch basin is harder than you might think, especially if it’s already installed and in need of repairs. Flexible liners are much easier to shape and insert in both new and existing basins. Sealant also tends to fail over larger cracks, while the right flexible liner can bridge most gaps as long as the basin itself is still stable.

Flexible Liner Benefits

Some of the greatest benefits of flexible catch basin liners include:

  • Relative low cost of installation thanks to reduced labor expenses
  • Lightweight materials are easy to move and cut openings for pipes, as long as you choose a high durability material like RPE
  • Custom fabrication allows for factory seam sealing, letting you just install the liner in with a perfect fit
  • Durability allows quality RPE liners from BTL to last decades, especially when installed underground and away from the sun’s damaging UV rays
  • Easy to inspect and test for leaks with a range of equipment options
  • Improves the cleaning process by creating a smooth barrier between silt and the rough concrete surface
  • Resists damage from any chemical compounds mixed into the storm water, especially if you choose multi-layered RPE.

Which Flexible Liner Materials Work for Custom Catch Basins?

Most flexible liners sold for pond or canal use are less than ideal for the tight space of a catch basin. Choosing any old pond liner you find will only lead to unnecessary maintenance and repair costs. Some liners just can’t handle the chemical exposure possible in a storm water system, while others are too thick and heavy to fold into a smaller catch basin corners. Pick the right flexible liner material for your catch basins by comparing the following options.

  • Reinforced polyethylene (RPE): A multi-layered RPE liner, such as BTL Liners’ ArmorPro, is the best option for lining a catch basin of any size. It’s lighter and thinner than other liners without sacrificing any durability or chemical resistance. This reduces shipping costs and eases installation. It’s easy to custom fabricate with factory welded seams and can last decades. The reinforced design and multiple layers of both HDPE and LDPE make it one of the most chemical and tear resistant liners on the market.
  • Ethylene propylene diene terpolymer (EPDE): This thick and relatively stiff material was first designed for protecting low slope roofs from water damage. While they were quickly re-purposed into pond liners, most EPDE products aren’t designed with underwater use in mind. This means that some formulas add chemicals to the mix that could react with compounds in the runoff water. EPDE is heavy, difficult to fit into tight corners, and is generally not a good choice for catch basins or storm water systems.
  • Polyvinyl chloride (PVC): PVC may work well for the drainpipes used to connect the rest of the drainage system, but it’s not a great liner for ponds or catch basins used to hold storm water. A risk of chemical leaching occurs with PVC liners, in addition to lower durability and strength. The material is softer than EPDE and easier to shape, but it must come in a thicker sheet than RPE to offer the same level of strength. Most PVC liners also offer shorter lifespans than RPE products, especially when exposed to a wide range of chemicals on a regular basis.
  • High- and low-density polyethylene (HDPE and LDPE): Both forms of polyethylene liner work well for fishponds and other uses, but they’re best when combined into multi-layer RPE for intensive uses like catch basins. Combining layers of both types of polyethylene provides the greatest blend of chemical resistance and physical strength, especially when you add in the reinforced design. Stick with RPE rather than trying to choose between HDPE and LDPE for storm water systems.

With so many types of flexible liners available, there’s no need to settle for what’s already available in your area. BTL Liners is happy to ship any amount of RPE liner anywhere it’s needed in the world, ensuring you always get the reliable materials you need for important storm water management projects.

Routine Inspection and Testing

Trying to force a stiff piece of EPDE rubber into a catch basin will only frustrate you and your workers. Make it easy to line, inspect and test your custom catch basins and other parts of the storm water system, by choosing a truly flexible liner product. Stick with multi-layered RPE from BTL Liners to quickly and efficient protect your system from seepage and leaks. No matter what liner you choose, always remember to inspect it at least once every six months.

Liners by BTL

AquaArmor Pond Liner

The most versatile liner on the market today, AquaArmor maximizes protection from harmful UV rays, tear resistance and punctures that cause leaks. Simply the best liner on the market.

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