Quick Answer

Most pressure washers can apply detergent using either a detergent bottle attached to the spray gun or a built-in detergent tank. Depending on your model, detergent is only dispensed when the variable pressure nozzle is set to the low-pressure setting.

Tip: Only use detergents specifically designed for pressure washers. Using unsuitable cleaning chemicals may damage your machine and could invalidate your warranty.

Before You Begin

Before using detergent:

• Read and understand your product manual.
• Only use detergents recommended for pressure washers.
• Wear appropriate personal protective equipment (PPE), including gloves and eye protection.
• Avoid contact with skin, eyes and clothing.

Warning: Detergents can cause irritation or burns. If detergent comes into contact with your skin or eyes, rinse immediately with plenty of clean water. Seek medical advice if irritation persists, and have the product container or label available.

Which Detergent System Does My Pressure Washer Use?

Pressure washers generally use one of the following detergent systems:

• Detergent bottle attached to the spray gun
• Built-in detergent tank

Refer to your user manual if you are unsure which system your model uses.

Option 1: Using a Detergent Bottle Attached to the Spray Gun

The following models use a detergent bottle that attaches directly to the spray gun:

• Qualcast Q1W-SP09-1450
• Spear & Jackson Q1W-SP09-1450
• McGregor MPW1470
• Most cordless pressure washers

How to Use the Detergent Bottle

1. Prepare your detergent solution according to the detergent manufacturer's instructions.
2. Unscrew the detergent bottle cap.
3. Fill the bottle with the diluted detergent solution.
4. Securely tighten the cap.
5. Attach the detergent bottle to the spray gun.
6. Turn on the pressure washer.
7. Pull the trigger to begin applying detergent.

The detergent will automatically mix with the water as you spray.

Applying Detergent

For best cleaning results:

• Apply detergent to a dry surface.
• Work from the bottom upwards.
• Allow the detergent to work for the recommended time.
• Do not allow the detergent to dry on the surface.

Rinsing

After cleaning:

• Switch to clean water.
• Rinse using high pressure.
• On vertical surfaces, rinse from the bottom upwards, then finish from the top down to help prevent streaking.
• Hold the nozzle approximately 15–20 cm (6–8 inches) from the surface at roughly a 45° angle.

Option 2: Using a Built-In Detergent Tank

Many pressure washer models feature an integrated detergent tank.

Filling the Detergent Tank

1. Prepare the cleaning solution.
2. Engage the spray gun safety lock.
3. Remove the detergent tank cap.
4. Pull out the detergent feed hose if fitted.
5. Fill the tank with the diluted detergent solution.
6. Refit the hose and securely replace the cap.

Applying Detergent

To dispense detergent:

1. Fit the variable pressure nozzle to the spray gun.
2. Set the nozzle to the lowest pressure setting.

Depending on your model:

• Twist the nozzle to the low-pressure position, or
• Pull the nozzle forwards into the low-pressure position.

Important: Detergent will only be drawn through the machine when the variable pressure nozzle is set to the low-pressure setting.

3. Release the safety lock.
4. Pull the trigger to begin applying detergent.

Tips for Best Results

• Always dilute detergent as instructed by the detergent manufacturer.
• Only use pressure washer-approved detergents.
• Never use bleach, acids or corrosive cleaning chemicals.
• Rinse the detergent system with clean water after use to prevent residue build-up.

Frequently Asked Questions

Why isn't my pressure washer dispensing detergent?

The most common reason is that the variable pressure nozzle is not set to the low-pressure setting. Also check that the detergent tank or bottle contains diluted detergent and that the feed hose is not blocked.

Can I use washing-up liquid or household cleaners?

No. Only use detergents specifically designed for pressure washers. Household cleaning products can damage seals, pumps and internal components.

Why should I apply detergent to a dry surface?

Applying detergent to a dry surface allows it to cling more effectively and improves cleaning performance.

Can I use detergent with every nozzle?

No. On most models, detergent is only drawn through the machine when using the variable pressure nozzle set to its lowest pressure setting.

Should I flush the detergent system after use?

Yes. Running clean water through the detergent system after use helps prevent blockages and prolongs the life of your pressure washer.