What Are The Drain Tubes On A Tonneau Cover For? Here's How They Work

One of the main reasons you get a tonneau cover for your truck bed is to protect the bed and its contents from the elements, particularly rain. However, covers aren't completely waterproof, and water doesn't just disappear after it hits something; it accumulates, weighs things down, and eventually, pierces through. Depending on how your truck's tonneau cover is designed, there may not be an avenue for the water that accumulates on its surface to safely slide away. It could either start to weigh and warp the cover or gradually snake its way beneath into the bed.

Luckily, high-rated tonneau cover manufacturers understand this, which is why hard and folding covers have an additional measure to keep both the cover and your bed safe from water accumulation: a pair of drain tubes. It's a simple, yet clever concept: if there's too much water building up on the surface of the cover, just drain it all away from the truck. Drain tubes, working in concert with gutter or water storage systems, facilitate that safe drainage process, ferrying water out the back or bottom of the truck and away from your precious cargo.

When you first installed your tonneau cover, there may have been either a storage can or a set of gutters integrated into the setup. These are what allow the drain tubes to do their job. When large quantities of water fall onto the cover, its angle naturally steers it toward a gutter or drainage system, where it flows down into the drain tubes. The tubes are connected to a drainage pipe within the truck's bed, which your truck either came with or you drilled yourself as part of the cover installation process. When the water reaches the end of the line, it dribbles out safely through a designated exit point, landing on the ground near your truck.

What all this amounts to is a convenient way of isolating the inside of your truck's bed from the outside world. Thanks to the rubber and plastic construction of your drainage tubes, the water remains separate from the inside of the bed, even though it's technically flowing right next to it, and then pops out the bottom of your truck. It's the same basic concept as a rain gutter, just with a flexible element so it can fit easily inside your truck bed and beneath your tonneau cover.

It is worth noting, however, that drain tubes can wear down over time, either from bouncing around inside the bed or funneling large quantities of water. Luckily, most models of tonneau covers that support drain tubes also allow you to replace them with a quick installation. You can get replacement tubes from brands that make tonneau covers like Bakflip or Retrax.