How to Apply Thompson’s Water Sealer With a Sprayer

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If you’re a seasoned woodworker or DIYer, you may know the Thompson’s water seal as a top product that shields decks from elements like rain and direct sunlight. Applying this sealer is not complicated, but it can be challenging to master, and if you make a mistake, you risk destroying the whole project.

So, allow me to guide you through the steps of using a sprayer to apply Thompson’s water seal, drawn from my experience in sealing decks and other outdoor projects.

Applying Thompson’s Water Seal with Sprayer Guide

Materials You’ll Need

Step #1: Clean Your Deck (How to Do it Properly)

Waterproofing any surface requires thorough cleaning of the area that will be treated. Sweep away the leaves, sticks, and other junk with a broom.

washing deck

Make sure to sweep everything that can get in the way—anything wedged between the boards can be a real issue. If there’s debris on the surface, the sealer might not properly reach the edges of the decking planks. Always make sure to clear that out first.

Aside from sweeping your deck boardsm you can also use a power washer on all the surfaces. High-pressure water spraying is an effective option to clean the surface and bring back the wood’s original color

For maximum protection, do not apply the sealer to the deck for at least 48 hours after cleaning.

Step #2: Safeguard Adjacent Lawn & Objects

To avoid accidentally staining the grass while dealing with the driveway or deck, lay down a protective sheet or tarp. Also, the lawn can be damaged by any chemicals you’ll apply, so make sure you lay out a cloth first.

If your deck is attached to your home, you should protect the siding by taping it off or using masking tape/paper.

protective sheets on the grass

You can examine the deck for any loosened fasteners after four days. The liberated metals can be rammed into position using a hummer or a drill. Get rid of anything else that could cause injury using the scraper or utility knife.

Following that, remove the debris by sweeping, allowing the deck finish to dry naturally. However, it is worth noting that Thompson’s water seal can be applied to damp wood.

Step #3: Prepare Your Sealer

Get some Thompson’s water seal, shake the can thoroughly, and pour the contents into your lawn sprayer’s container. Put a cloth down first to catch any messes you make while transferring.

Step #4: Start Spraying the Deck

Before applying the Thompson’s water seal or using a sprayer, I always take a moment to thoroughly read through the sealer’s or paint manufacturer’s guide. Trust me, it’s essential for ensuring the best protection against rain and sunlight.

Make sure the first coat seals the entire surface, including the railings evenly by using a garden sprayer, plastic sprayer with a brass wand, pump sprayer (pump up garden sprayer), or any suitable sprayer of your personal preference.

staining deck with sprayer

If the sealer is not applied uniformly with a pump sprayer, you may switch to a paintbrush for the corners. Rags can be used to wipe away any unapplied sealant or paint before proceeding with the application or a second coat.

Step #5: Let the Deck Surface Dry

You should let the water seal and wood dry for 24 hours after you seal with a sprayer.

Determining how long the drying time will take depends on factors like humidity and temperature. For instance, if you just waterproofed your new deck or fence, and it’s freezing outside, it can take more than 24 hours to completely dry.

How to Choose the Best Sealers for Your Sprayer

Solid Stains

These stains have the most significant thickness and can provide the best possible defense for wood. Each deck board is protected from the sun’s rays and water by waterproofing products that are also tinted to hide the color of the solid stain.

Behr Solid Color Waterproofing Stain and Sealer

Only one coat of solid stain prevents the new wood from water damage or fading due to exposure to ultraviolet light.

Semi-Transparent Stains

Waterproofing and considerable UV protection are benefits of the many different hues available for a semi-transparent stain.

The best semi-transparent stain improves the look of your decking boards while allowing you to see the wood grain thanks to its hues and the paint thinner or mineral oil consistency. [1]

Clear Sealers

This sealer has no color, as the name implies. Due to this, it provides very little shade or minimal protection from the sun. 

If you want your wood to retain its natural color, a thin layer of clear sealer is a way to go.

Valspar One-Coat Semi-Transparent Stain Sealer

While choosing deck sealers, remember that the water sealant’s lightness will directly correlate to how often it will need to be reapplied.

For the best results, choose a clear sealer that could shield the wood from too much exposure to water and UV rays.

Our Handpicked Recommendations for Water Seal Sprayers

1. Deck & Home 190399 Universal Sprayer

I’ve found this garden sprayer to be perfect for Thompson’s Waterseal and products of its kind. It’s unique—unlike many others I’ve seen. It is tailored for lower-density, water-based sealers, but it can also handle common tasks like insecticides, weed killers, bleach, and water seamlessly.

Its 2-gallon tank was designed to work nonstop. This garden sprayer’s high-end shutdown feature ensures you can spray continually, even if you don’t press the trigger.

What I Like

What I Don't Like

2. Smith 190285 1-Gallon Bleach and Chemical Sprayer

There aren’t a lot of fancy features on the D.B. Smith Bleach & Chem sprayer, but the simplicity of its design makes it ideal for a task that needs you to apply Thompson water seal.

This sprayer holds one gallon of liquid and has a wide opening for easy restocking. The final step is to compress the canister and begin spraying. It includes a locking trigger for constant usage and is suitable for a wide range of surfaces, from decks to sidings.

What I Like

What I Don't Like

3. Chapin International 20541

Having used the Chapin 20541 myself, I can vouch for its versatility. You’ve got options with a 1-, 2-, or 3-gallon tank. Now, the Thompson’s water seal does come in different sizes, and the one you go for really depends on your usage. Just remember, as the size goes up, so does the price.

Next, the large opening and transparent design make it simple to see when a refill is necessary. A time-saving and tool-preserving in-tank anti-clog filter is included.

What I Like

What I Don't Like

When Should You Seal Your Deck? Here are Signs Your Deck Needs Waterproofing


Always check the surface of an older deck for signs of deterioration. Black patches not caused by oily stains or debris could result from mold and mildew.

The presence of dirt and water are ideal conditions for the growth of both mildew and algae. In other words, if they are there, it’s a sure sign that the deck boards are soaking up enough water to support mold and algae.

Graying Wood

Unfinished wood ages to a silvery gray patina. Grey deck boards indicate that the timber has not been treated and is susceptible to weather conditions.

old deck

Visible Cracks

If the exterior wood absorbs water, it expands. The wood shrinks as moisture is removed. Wood will eventually crack if it undergoes continual swelling and shrinking.

This kind of wood might deteriorate and harm your loved ones. Wood is susceptible to structural damage from moisture or weather patterns, but waterproofing helps prevent it.

Wood Absorbing Water (Splash Test)

In my line of work, there’s a simple test I often use to gauge if a deck truly needs waterproofing. Just splash some water around the deck and observe the results. It’s a straightforward way to get a clearer picture.

newly stained deck

Wood that darkens after exposure to water indicates that it’s porous and should be sealed. But if water beads on the wood, it is already protected and doesn’t need to be waterproofed.

Standard Rules for Applying Thompson’s Water Seal Using a Sprayer


What type of brush should I use for applying Thompson’s water sealer?

When applying the Thompson’s seal, a synthetic bristle brush or a medium nap paint roller will suffice as good alternatives to a sprayer. Certain water-based coatings discourage using a roller, suggesting that a paint pad be used instead.

Read Next


Now that you know how to apply Thompson’s water seal with a sprayer the proper way, you can put this expertise into practice for numerous projects. Deck cleaners, paints, and sealants can catch fire, so consider that as well. 

Additionally, I’d advise sticking to the manufacturer’s disposal instructions for any leftover materials.

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Robert Johnson is a passionate furniture maker & carpenter, sought after for his knowledge on the craft.
You’ve probably seen his down-to-earth wisdom in USA Today, Bobvila, Family Handyman, and The Spruce, where he has shared commentary and guidance on various woodworking topics.

Robert is the brain behind Sawinery, where he aims to share tips, tricks, and a passion for all things carpentry.

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