The DIY Guide to Pressure Washing Your Deck Like a Pro

Introduction

This guide provides a high-level overview of the process of pressure washing a deck. While it covers key concepts and techniques, always conduct further research and consider professional assistance if you are unsure about any step.

Many of these recommendations come from years of experience, trial and error, and lessons learned from real-world scenarios. Other professionals or industry experts may use different methods or disagree with our practices. However, we proudly maintain nothing but 5-star reviews on Google and an A rating with the Better Business Bureau, giving us full confidence in our strategies and approach.

As the warmer months approach, getting your outdoor space clean and ready for relaxation is a top priority. One of the most effective ways to refresh your deck is through surface cleaning, which involves using high-pressure water and a strong cleaning solution to remove dirt, mold, mildew, and other grime. This particular guide is dedicated to composite decks and vinyl railings, such as those made from Trex or Azek. While many of the techniques discussed here can be applied to other types of decks, some methods can cause permanent damage to wood surfaces like pressure-treated, stained, cedar, teak, and other similar materials. If you are looking for guidance on cleaning wood decks, stay tuned for a comprehensive guide coming soon.

In this guide, we'll cover everything you need to know to properly pressure wash your deck, including the best tools, cleaning solutions, and techniques to get the job done right.

Tools and Equipment Needed

Choosing the Right Pressure Washer

Pressure washers come in two types: electric and gas-powered. While electric models are great for small, light-duty jobs, gas-powered pressure washers provide the higher pressure (PSI) and greater water flow (GPM) needed for effective deck cleaning.

For best results, you'll want a pressure washer with:

• Minimum 2500 PSI (pounds per square inch) for adequate cleaning power

• At least 4 GPM (gallons per minute) for improved efficiency and effectiveness

A higher GPM rating allows the pressure washer to rinse away debris faster and clean larger areas in less time. These gas-powered machines can usually be rented from most power equipment rental stores if you don’t own one.

Pressure Washer Nozzles and Surface Cleaners

Your pressure washer does not do all the work alone—the nozzle selection is key to proper cleaning without causing damage.

Most machines come with four standard tips:

• Red (0°): Ultra-high pressure, not recommended for deck cleaning

• Yellow (15°): High pressure, good for heavy stains but should be used cautiously

• Green (25°): Medium pressure, good for general cleaning

• White (40°): Low pressure, best for rinsing and gentle cleaning

For cleaning composite decks like Trex or Azek, the white (40°) tip is the best choice to avoid damage.

Another game-changing tool is a surface cleaner, which attaches to your pressure washer and features spinning nozzles that provide an even, controlled clean. This can drastically cut down on labor time and improve results, but it’s important to test in an inconspicuous area first to ensure it won’t leave etch marks. It is also critical to ensure your surface cleaner is properly matched to your pressure washer’s specifications, including PSI (pressure) and GPM (water flow). Using a surface cleaner that requires higher GPM than your machine provides can lead to poor performance or ineffective cleaning. Be sure to check your pressure washer’s specifications and match it with a compatible surface cleaner for optimal results.

Applying Cleaning Solution

There are two primary methods for applying cleaning solutions:

1. Pressure Washer Soap Injector: Many pressure washers have a built-in detergent injector that automatically dilutes the solution (typically 10:1 or 20:1 dilution ratios). Knowing your machine’s draw rate is important to avoid over-diluting your cleaner.

2. Pump Sprayer: A manual or battery-powered sprayer allows you to apply a stronger cleaning mix since it doesn’t dilute the solution. This is ideal for tough stains and heavily soiled decks.

   
   

Choosing the Right Cleaning Solution

Note: We will discuss cleaning and maintaining bare and pressure-treated wood decks in a future blog post. A bleach-based cleaning solution is ideal for decks made of composite materials and vinyl hand rails, especially for those with organic growth like mildew or moss. However, for bare or stained wood decks, a peroxide-based cleaner should be used to avoid damaging the wood grain or altering the color.

Mixing Bleach Solutions for Cleaning

For deck cleaning, you typically want a final solution between 1% and 3%, so adjust your bleach-to-water ratio accordingly. Bleach solutions can be mixed based on the severity of the staining:

• Light Soiling: 1% bleach solution (1 part bleach to 9 parts water)

• Moderate Soiling: 2% bleach solution (1 part bleach to 4 parts water)

• Heavy Mold/Algae: 3% bleach solution (1 part bleach to 3 parts water)

Bleach can be sourced from:

• Grocery stores (regular household bleach, ~6%)

• Pool supply stores (pool shock, 10%-12.5%)

Adding Surfactants: To help your cleaning solution cling to the surface and work more effectively, add a bleach-safe surfactant (this detail can be found on the products label)  such as Dawn dish soap or Gain laundry detergent (about 1 oz per gallon of solution).

Bleach concentrations vary, so it’s important to adjust your mix accordingly for effective deck cleaning. Below are the proper dilution ratios for 6%, 10%, and 12.5% bleach to achieve a 1%, 1.5%, 2%, or 3% cleaning solution:

• For 6% Bleach (Household Bleach):

  • 1% solution → 1 part bleach to 5 parts water

  • 1.5% solution → 1 part bleach to 3 parts water

  • 2% solution → 1 part bleach to 2 parts water

  • 3% solution → 1 part bleach to 1 part water

• For 10% Bleach (Pool Shock):

  • 1% solution → 1 part bleach to 9 parts water

  • 1.5% solution → 1 part bleach to 6 parts water

  • 2% solution → 1 part bleach to 4 parts water

  • 3% solution → 1 part bleach to 3 parts water

• For 12.5% Bleach (Stronger Pool Shock):

  • 1% solution → 1 part bleach to 11 parts water

  • 1.5% solution → 1 part bleach to 7 parts water

  • 2% solution → 1 part bleach to 5 parts water

  • 3% solution → 1 part bleach to 3 parts water

These mixtures allow for the correct dilution based on the severity of the grime while ensuring that the bleach remains effective without causing unnecessary damage.

Precautions When Using Bleach

Bleach is powerful, but it comes with risks. Here are some safety precautions:

• Protect plants and grass: Saturate surrounding vegetation with fresh water before and after applying bleach to neutralize any runoff.

• Wear PPE: Use gloves, goggles, and protective clothing to avoid skin and eye irritation.

• Avoid prolonged exposure: Do not let bleach sit on the deck too long, as it may cause discoloration.

Step-by-Step Deck Cleaning Process

Step 1: Pre-Rinse and Protect Surrounding Areas

Before applying any cleaning solution, pre-wet surrounding plants with fresh water to minimize chemical absorption.

Step 2: Apply the Cleaning Solution

• Using a pump sprayer or soap injector, apply the cleaning solution generously. A pump sprayer is usually necessary for railing application, as railings often accumulate heavier organic grime that requires a stronger mix and precise application.

• Focus on heavily soiled areas and let the solution dwell for 5-10 minutes.

• Be mindful that overspray from cleaning solutions can travel long distances beyond the deck, so take precautions by saturating grass and plants before and after cleaning to prevent damage.

• Avoid letting the solution dry before rinsing.

• Using a pump sprayer or soap injector, apply the cleaning solution generously.

• Focus on heavily soiled areas and let the solution dwell for 5-10 minutes.

• Avoid letting the solution dry before rinsing.

Step 3: Pressure Wash Using the Right Nozzle

• If using a surface cleaner, test a small area first to ensure it doesn’t leave marks.

• Move slowly, covering every section twice in a methodical, overlapping pattern.

• If using a pressure washer gun, use a white (40°) tip and maintain a safe distance.

• For railings, slightly higher pressure may be needed. A yellow (15°) tip can be used cautiously for tougher grime.

• Always spray entire boards from end to end to prevent visible etch lines.

• If using a surface cleaner, test a small area first to ensure it doesn’t leave marks.

• Move slowly, covering every section twice in a methodical, overlapping pattern.

Step 4: Rinse Thoroughly

• Switch to a low-pressure nozzle (black tip), which can be identified by the large hole in the center and its low-pressure discharge. As always, test in an inconspicuous area first to avoid any potential damage.

• For railings, use the same black tip for a safe and thorough rinse.

• Rinse the deck completely, ensuring all detergent and grime are fully washed away.

• Re-rinse surrounding areas (plants, grass, railings) to neutralize any remaining bleach.

• For those who are more cautious or sensitive to bleach, a neutralizing agent such as Agent Halt can be used to neutralize any remaining bleach on surfaces and surrounding vegetation. This product helps stop the chemical reaction of bleach, preventing potential damage to plants and reducing any lingering bleach residue. Always follow the manufacturer’s guidelines for proper dilution and application to ensure safe and effective use. You can purchase Agent Halt here.

  
  

Final Thoughts

By following these steps, you can safely and effectively pressure wash your deck, restoring it to a clean and refreshed state. Using the right pressure, cleaning solution, and technique will help you avoid common pitfalls like damaging wood, leaving etch marks, or wasting time with inefficient cleaning methods.

Taking the extra time to apply the correct cleaner and use the right tools will make your deck look brand new without unnecessary effort. With proper care and maintenance, you’ll enjoy a clean, inviting outdoor space all season long!

Disclaimer

This guide is for informational purposes only. Elite House Wash LLC cannot be held responsible for any property damage, physical harm, or injuries resulting from the use of cleaning solutions or pressure washing equipment. If you are not confident in your DIY abilities, it is always a good idea to leave the job to an experienced and insured professional.