How to do soft washing with a pressure washer

September 16, 2025

BISON Santy

Hello, I am Santy, the funder of bisonclean.com. I have been in cleaning machinery field for more than 5 years now, and the purpose of this article is to share with you the knowledge related to pressure washer from a Chinese supplier's perspective.

Soft washing with a pressure washer is a safe and effective way to clean delicate outdoor surfaces without causing damage. Unlike traditional pressure washing, which relies on high-powered water to blast away dirt, soft washing uses low pressure combined with specialized cleaning solutions to gently remove mold, mildew, algae, and grime.

This beginner-friendly method is ideal for roofs, siding, fences, and decks that can’t handle strong water force. In this guide, BISON will explain how soft washing works, why it’s a smarter choice for certain cleaning jobs, and how to properly use a pressure washer for soft washing.

What is soft washing?

Soft washing is a gentle cleaning method that uses low water pressure—typically between 100 and 500 psi—along with specialized cleaning solutions to safely clean surfaces.

Here’s how it works:

The cleaning solution is sprayed onto the surface and allowed to sit for a few minutes.
It kills mold and algae at the root, loosens dirt, and dissolves stains.
The surface is then rinsed with low-pressure water, leaving it clean and damage-free.

Unlike traditional pressure washers, which can exceed 2,000 psi and potentially damage delicate materials, soft washing relies on detergents to break down dirt, mold, algae, and other contaminants, killing the spores that cause mold and algae growth rather than simply washing them away. This allows soft washing to not only clean and protect delicate surfaces, but also provide a longer-lasting clean.

Tools and supplies needed for soft washing

1. Pressure washer (with adjustable settings)

A pressure washer with adjustable psi settings is essential for soft washing. Since soft washing requires less than 500–1000 psi, choose a model with:

Adjustable pressure settings (to prevent surface damage).
Gas or electric power options (gas-powered units offer more mobility for large areas).
Detergent injection system (downstream or upstream injectors to apply cleaning solutions safely).

2. Downstream injector

A downstream injector mixes your cleaning solution into the water flow after it leaves the pressure pump. This keeps harsh chemicals from running through the pump, preventing equipment damage while making solution application faster and safer.

3. Soft wash nozzles

For soft washing, use low-pressure nozzles that spread the cleaning solution evenly without damaging delicate surfaces. Recommended nozzles include:

Black nozzle (65°) – low pressure, ideal for applying chemicals.
Soap nozzle – specifically for detergent application.
White nozzle (40°) – for gentle rinsing on soft surfaces.

4. Cleaning solutions

Soft washing uses specially mixed cleaning solutions to remove mold, algae, and stains:

Basic soft wash mix (light cleaning)

1 part household bleach (5.25% sodium hypochlorite)
3 parts water
1 oz dish soap per gallon (to help the solution stick)

Heavy-duty mix (tough stains)

1 gallon of water
1 cup sodium hydroxide
A few drops of surfactant or soap

Safe mixing steps:

Wear safety gear such as gloves, goggles, long-sleeved shirts, and a mask or respirator, and choose a well-ventilated area.
Use a clean bucket for mixing.
Mix the ingredients according to the ratio of a basic cleaning solution or a heavy-duty cleaning solution. Always add water first, then the chemicals.
Stir gently to avoid splashing.

Caution: Never mix bleach with ammonia or other cleaning agents—toxic fumes may form.

Step-by-step guide to soft washing

Step 1: Clear and protect the area

Remove obstacles: move outdoor furniture, toys, tools, and fragile items away from the work area.

Cover plants and landscaping: Use plastic sheeting or a tarp to shield plants from cleaning chemicals.

Pre-rinse plants: Wet plants with clean water before and after spraying to reduce chemical damage.

Close windows and doors: prevent water or chemicals from entering buildings.

Turn off outdoor electricity: cover outlets and lights to avoid electrical hazards.

Step 2: pre-rinse dirty surfaces

If the surface has heavy dirt or dust, use plain water at low pressure to loosen debris. This makes the cleaning solution work better and prevents streaking.

Step 3: Apply the cleaning solution

Start at the bottom: work upward to prevent streaks.

Use a soft wash nozzle: keep 2–3 feet from the surface for even coverage.

Let it sit 5–15 minutes (dwell time): Wait for the solution to break down dirt, mold, and stains. If it starts to dry out, lightly spray it again.

Reapply to stubborn stains: If you see areas with heavy buildup, apply a second coat.

Step 4: Rinse thoroughly

Switch to clean water and the white 40° nozzle for a gentle rinse.

Using the same low-pressure setting, rinse from top to bottom to remove all cleaning solution and residue.

Check for missed spots and rinse again if needed.

Rinse plants and nearby surfaces to remove any chemical runoff.

Step 5: Post-rinsing inspection

Look over the entire area for streaks, stains, or mold that wasn’t fully removed. If necessary, repeat the cleaning solution and rinsing steps.

Step 6: Clean and store equipment

Pressure Washer: Flush the system with clean water for several minutes to prevent damage from harsh chemicals.

Nozzle, hose, and sprayer: Rinse with clean water and inspect for dirt or blockage.

Storing Chemicals Safely: Allow all items to dry before storing. Please store this product in a dry and ventilated place, avoiding moisture and direct sunlight.

Best surfaces for soft washing

Surface	Best For	Benefits
House siding and exterior walls	Vinyl siding, wood, brick, stucco, fiber cement, and painted surfaces	Preserves paint and siding, prevents cracking or chipping, restores curb appeal
Roofs	Asphalt shingles, tile roofs, metal roofs, cedar shakes	Prevents roof deterioration, extends lifespan, reduces algae regrowth
Decks, fences, and outdoor wood structures	Wood fences, composite decks, gazebos, pergolas	Removes mold and algae, prevents cracking, maintains wood integrity
Windows and screens	Glass and screens	Gentle, streak-free cleaning without breakage or tearing
Outdoor furniture and awnings	Fabric, vinyl, or painted surfaces	Cleans safely, prolongs lifespan, prevents wear or tearing
Solar panels	Solar panel glass surfaces	Maintains efficiency, prevents damage from abrasive cleaning methods

Conclusion

With proper preparation and safety measures, even beginners can confidently handle soft washing. By preparing the area, mixing the cleaning solution properly, applying it with low pressure, allowing it to work, and rinsing thoroughly, you can achieve excellent results while protecting your property. Whether you’re cleaning a roof, restoring a wooden deck, or maintaining your home’s exterior, the right equipment, cleaning solutions, and methods make all the difference.

As a professional pressure washer manufacturer in China, BISON independently develops, produces, and sells high-quality pressure washers and accessories designed to provide reliable performance and long-lasting cleaning results. Contact us today to import the BISON pressure washer series from China and experience a safe and convenient purchasing process and a pressure washer that’s designed with meticulous attention to detail!