If you own a pickup truck, you likely use the bed to haul equipment, tools, and other cargo that you want to keep protected from the elements. But when it starts raining, will a tonneau cover actually keep your truck bed dry?
How Do Tonneau Covers Work To Keep Out Water?
A tonneau cover sits on top of the truck bed, fastening to the sides and tailgate to create a tight seal. This seal prevents most water from entering the bed during rain showers. Tonneau covers come in different styles:
Hard Tonneau Covers
Made from aluminum, fiberglass, or ABS plastic, hard covers create the tightest seal against water. The rigid panels don’t sag or flap in the wind. Hardware clamps tightly to the bed sides for minimal water intrusion.
Soft Roll-Up Covers
With a vinyl or canvas exterior rolled around an aluminum frame, roll-up covers can unroll to cover the bed fully. The ends attach firmly to the bed sides to minimize water getting in.
Retractable Tonneau Covers
Also known as rolltop covers, retractable versions roll up toward the cab instead of needing removal for full bed access. The vinyl exterior still latches tightly when fully extended.
Snap-On Tonneau Covers
Made of leather or vinyl, snap covers secure to the bed sides with snaps instead of clamps. These allow quicker installation but may let more water intrusion than clamping versions.
Folding Tonneau Covers
Folding covers use vinyl panels that accordion fold toward the cab. Side rails ensure a tight fit to keep out rain when fully extended.
So while designs vary, tonneau covers all work to create a water-resistant barrier over the truck bed. But are they 100% watertight?
Are Tonneau Covers Completely Waterproof?
While tonneau covers are designed to keep truck beds dry, most are not completely waterproof. Why not?
Gaps around edges allow some water in
Even when secured firmly, small gaps may exist along the tailgate, tops of bed walls, and corners. Wind-driven rain can infiltrate these spaces.
Seals wear over time
Clamps, snaps, and hook fasteners can loosen with use, potentially compromising the tight seal. Vinyl and fabric covers also stretch slightly over time.
Temporary removal breaks the seal
Opening the cover to access the bed allows moisture to enter until it’s replaced. Frequent opening and closing deteriorates seals quicker.
Imperfect truck bed allows leaks
Dents, damage, or rust holes along the bed walls or tailgate can allow rainwater to leak through. Aftermarket accessories like bed liners can also hinder sealing.
Driving factors such as speed affect covers
At highway speeds, wind force and airflow over the tonneau can allow water to penetrate fabric covers and clamps. Hard covers withstand wind better.
So while tonneau covers are water-resistant, most are not 100% waterproof. But they still provide excellent protection in most rainy conditions when properly installed and maintained.
How Much Water Can Get In With A Tonneau Cover?
With a tight-fitting, well-sealed tonneau cover, only a very small amount of water will get into your truck bed in average rainstorms. Here’s why you can expect your cargo to stay mostly dry:
Vinyl and canvas covers repel water well
The woven fabrics used resist water infiltration, causing most raindrops to bead up and roll off the exterior surface.
Minimal gaps keep out drenching downpours
Even though small gaps may exist around the edges, the cover itself extends over the entire bed to deflect the majority of rainfall.
Proper drainage prevents pooling
Quality covers employ drainage channels, tubes, or gaps to prevent standing water puddles on top that could leak through stitching.
Hard covers offer superior protection
Rigid aluminum or reinforced panels are exceptionally water-resistant. They also withstand wind and pressure from pooling water.
Bed rail caps further prevent drips into the bed
Many tonneau covers integrate rail caps that close off gaps along the top of the bed walls where water could drip down into the truck bed.
Parking angle impacts results
Parking on an incline allows water to run off the cover instead of pooling in spots. Parking under cover further reduces exposure.
While performance differs between top-tier premium covers versus budget versions, most will only allow a minimal amount of water to seep in during average rainfall.
How Can I Improve The Water Protection Of My Tonneau Cover?
If you want the most waterproof tonneau cover possible, here are some tips:
Choose a premium hardcover model
The most impenetrable to water are hardcovers made from thick aluminum or reinforced composites. Opt for robust construction.
Ensure proper ongoing maintenance
Check clamps and seals regularly. Clean the cover, treat the vinyl, and replace worn gaskets as needed.
Install rail caps if absent
Adding bed rail caps seals gaps along the top of bed walls that could allow water intrusion.
Weatherstrip the tailgate
Self-adhesive weatherstripping tape closes any slight gaps between the tailgate and cover edge.
When possible, back in or park on high ground so water runs off the cover and flows away from the tailgate seam.
Use additional waterproofing treatments
Applying seam sealant minimizes leakage through stitching and fastening holes in soft covers.
Load cargo wisely
Avoid overloading the truck bed in ways that could compromise cover fit and tension on seals.
With the right tonneau cover design, installation, and maintenance, you can keep your truck bed essentially dry inside during wet weather driving.
How Much Rain Can Get Into A Truck Bed Without A Tonneau Cover?
Driving in the rain with an uncovered truck bed provides no protection against water intrusion. Here’s what to expect:
Driving duration impacts exposure
The longer you drive in rainy conditions without a tonneau, the more rainfall your cargo will be exposed to.
Heavy downpours will drench the bed
Without a barrier in place, pounding rains can quickly lead to soaked gear. Even tying down a tarp won’t prevent standing water.
Windblown rain comes in from all directions
Sideways rain, or water dripping down over the cab and tailgate will pour right into an open bed. A tonneau blocks this.
Road spray adds to the soaking
At speed, water flicks up under vehicles into the wheel wells and potentially the bed. It adds up over miles of driving.
The entire bed area remains vulnerable
Every square inch of the truck bed interior remains unprotected. Any item loaded there will get wet without a tonneau.
Removing the tailgate allows more water intrusion
The open tailgate cavity creates a larger exposure point for rainfall to enter if driving without doors or a gate.
Clearly, an uncovered truck bed offers zero protection against water getting inside. For keeping cargo and tools dry, a tonneau cover is essential.
Will A Basic Tonneau Cover Keep My Bed As Dry As A Premium Model?
Cheaper basic tonneau covers still repel water fairly well but may allow more leakage than premium versions. Here’s how they compare:
Vinyl covers are usually thinner
Less expensive covers often use lighter vinyl materials. Thinner fabrics resist punctures less and can sag more over time.
Minimal support structures may be weaker
Anti-pooling bows have less reinforcement. Thinner aluminum slats are used on basic rollup covers.
Securing hardware may be looser fitting
Snaps, tension knobs, and clamps on budget covers typically don’t cinch down as tightly. Gaps result.
Seals and edges tend to be less refined
Edge bindings, gaskets, and weatherstripping are simpler and less substantial.
Poorer drainage systems
Cheaper covers may lack effective channels, holes, or gaps to allow standing water runoff. Pools of water can leak through.
Less durable materials succumb to elements faster
Entry-level fabrics and finishes deteriorate more rapidly compared to premium brands. Seals fail sooner.
Minimal warranty coverage
Many manufacturers of economy tonneaus only provide a 1-3 year warranty. Premium brands offer 5+ years of coverage.
For occasional use or infrequent rain exposure, a value tonneau cover will provide fairly decent protection. But frequent haulers need a high-end cover for maximum dryness.
How Should I Maintain My Tonneau Cover To Keep My Truck Bed Dry?
Proper maintenance preserves your tonneau cover’s waterproofness over years of use. Here are some key maintenance tips:
Inspect seals and hardware regularly
Check for loose snaps, gaps in weatherstripping, cracked caulk, and claw tension on clamps. Tighten or replace as needed.
Keep the vinyl surface clean
Wash with soap and water, using a soft brush. Avoid harsh chemicals. Condition with protectants.
Drain water puddles promptly
Tip the cover or unroll periodically to drain off standing water so it doesn’t seep through.
Adjust fit around accessories
If adding a bedliner after installing the cover, readjust the clamps for a tight seam against the liner edges.
Lubricate rolls and hinges
Keep rolling parts moving freely by applying lubricant like silicone spray.
Patch any fabric holes or tears
Use adhesive vinyl patches to fix punctures in soft covers that could let in water.
Retighten fasteners over time
As connection points loosen from vibration, snug them up to maintain a solid seal all around.
With proper care and maintenance, a quality tonneau cover will uphold its water protection abilities for years of over-the-road use.
Will A Tonneau Cover Keep My Truck Bed Bone Dry
While tonneau covers are excellent at shielding your pickup truck bed from the majority of exterior water, most are not completely impervious. A small amount of liquid can still trickle in through minute gaps in seals, hardware, or protective coatings.
However, you can expect a high-end tonneau cover to provide almost bone-dry protection, especially if you take measures to enhance water repellency. Opt for durable aluminum, reinforced vinyl, robust clamping, and adequate drainage to keep your truck bed cargo protected against all but the most torrential downpours.
With reasonable care, your cover will continue shielding your gear from drizzle, showers, and even drenching rainstorms for years of reliable service. For light rain and average conditions, a tonneau cover will indeed keep your truck bed essentially bone dry.