Choosing the Right Orifice Size for Your Pressure Washer

When you're kitting out your pressure washer—whether that's with quick-connect nozzles or upgrading to a quality foam lance—getting the orifice size spot on is crucial. Regardless of the pressure washer you use, the wrong orifice can result in rubbish foam, pulsing issues, or worse, damage to your pressure washer. This guide will walk you through everything you need to know about orifice sizing, why it's so important, and how to choose the right size for your specific washer. We'll also cover why nozzle sizing differs from traditional foam cannon measurements and how proper matching keeps your machine running smoothly.

What is an Orifice?

An orifice is the tiny opening that controls how much water flows through your nozzle or foam cannon. Think of it as a traffic controller- it determines both the volume (measured in litres per minute) and pressure (PSI) of water passing through your system.

In car detailing setups, you'll typically find orifices in two key places:

• Foam cannons and lances (usually measured in millimetres, such as 1.1mm or 1.25mm).

• Quick-connect spray nozzles (referenced by flow rates like 030, 040, 045)

A smaller orifice restricts water flow, which increases pressure and often produces thicker foam when using a lance. However, go too small, and you'll cause your pressure washer to pulse, cut out, or fail to perform properly.

Understanding Flow-Based Orifice Sizing

When dealing with quick-connect nozzles or upgraded foam lances from brands like Mosmatic, the two most common sizes are:

• 030: Approximately 11 litres per minute (equivalent to 0.9mm).

• 040: Approximately 15 litres per minute. Ideal for high-output petrol machines (2500+ PSI).

The 030 is your go-to for less flowing machines, whilst the 040 works brilliantly with high-flowing, high-power setups. These codes assume a 40-degree spray angle, which is why "040" refers to both the angle and flow rate.

If you increase flow without matching your machine's pressure capability, you'll end up with reduced pressure and poor cleaning performance.

Understanding Nozzle Angles and Their Uses

Different spray angles serve specific purposes in your cleaning routine:

• 0° (Red): Concentrated jet for stubborn dirt and grime—use with caution on delicate surfaces.

• 15° (Yellow): Heavy-duty cleaning for driveways, patios, and tough stains.

• 25° (Green): General-purpose cleaning for most surfaces, including cars, fences, and walls.

• 40° (White): Wide, gentle spray perfect for rinsing and delicate surfaces.

• 65° (Black): Very wide, low-pressure spray ideal for applying detergents and soaps.

When upgrading to these systems:

1. Confirm your foam lance accepts standard 1/4" quick-connect nozzles.

2. Check the orifice size is appropriate (typically 030 for lower-flow machines, 040 for high-flow setups).

3. Consider purchasing a set of different orifices and angles to fine-tune results based on seasonal conditions or machine changes.

Choosing the Right Orifice for Your Machine

Here's how to ensure you're using the correct orifice size, whether in a spray nozzle or foam cannon:

Match Your Machine's Specifications

First, check your pressure washer's key specifications:

• PSI rating (pounds per square inch). Indicates maximum pressure.

• Flow rate (litres per minute). Determines water volume output.

Getting this pairing wrong leads to problems like using an undersized orifice, which leads to excessive pressure, machine strain, and pulsing issues. On the other hand, an oversized orifice causes problems like low pressure, weak foam, and disappointing cleaning results.

Recommended Orifice Ranges

Recommended Orifice Ranges by Machine Type

• Lower-flow electric machines like Karcher K2, K3, K4: 030 orifice or 0.9mm-1.1mm.

• High-flow electric machines like Karcher K5+, Nilfisk C110-C130: 040 orifice or 1.1mm-1.25mm.

• Professional electric machines like the AVA P70 or the higher-end Nilfisk models: 040 orifice or 1.25mm+.

• Petrol machines like the Kranzle K1622, K2160, and other high-end models: 040 orifice or 1.25mm+.

Always consult your user manual or manufacturer's sizing chart for the most accurate recommendations for your specific model.

Keeping Your Orifices in Top Form

To maintain peak performance:

• Flush thoroughly with clean water after every washing session.

• Inspect nozzles monthly for limescale buildup or wear.

• Replace brass orifices if the stamped size becomes worn or unreadable.

• Never use sharp metal objects to clear blockages. Use proper pin cleaners or compressed air instead.

Conclusion: Orifice Size Is Not One-Size-Fits-All

Whether you’re using a traditional foam cannon or upgrading to a quick-release detailing setup, orifice size matters more than most people realise. It impacts not just the thickness of your foam but also the performance and longevity of your pressure washer.

By choosing the correct orifice for your PSI/GPM range - and maintaining it regularly - you ensure better cleaning results, less machine wear, and a smoother wash process.