What is the difference between BAR and PSI in pressure washers?

BAR and PSI both measure pressure. 1 BAR = 14.5 PSI. For commercial cleaning, 100-150 BAR (1,500-2,200 PSI) is light duty, 150-200 BAR (2,200-3,000 PSI) is medium duty, and 200-350 BAR (3,000-5,100 PSI) is heavy duty. Most commercial applications fall in the 150-200 BAR sweet spot.

What is more important: pressure or flow rate?

Both matter equally. Pressure (BAR/PSI) blasts dirt off surfaces, while flow rate (L/Min) flushes the loosened debris away. High pressure with low flow leaves dirt behind. High flow with low pressure won't dislodge stubborn grime. For most commercial cleaning, 150-200 BAR at 12-20 L/Min is the ideal balance.

What is the difference between an axial pump and a plunger pump?

Axial pumps (or cam pumps) are simpler, cheaper, and found on light-duty residential units. They spin the pump head directly off the motor shaft. Plunger crank pumps (triplex plunger pumps) use a crankshaft-driven mechanism and are designed for continuous commercial and industrial use. They last 3-5 times longer than axial pumps but cost more.

What nozzle size do I need for my pressure washer?

Nozzle size is measured in orifice diameter. A general guideline: 2.0-3.0 mm orifice for 10-15 L/Min flow, 3.0-4.5 mm for 15-25 L/Min, and 4.5-6.0 mm for 25-40 L/Min. The wrong nozzle size either starves the pump (causing cavitation damage) or reduces cleaning power. Always match the nozzle to your machine's flow rate.

Why does my pressure washer keep shutting off?

The most common cause is a tripped thermal cut-out switch from overheating. This typically happens when the machine is run with the trigger closed (bypass mode) for too long. Always release pressure when pausing for more than 60 seconds. Other causes include low water supply, clogged inlet filter, or a faulty unloader valve.

Does higher BAR always mean better cleaning?

Not necessarily. Higher pressure is more effective at dislodging stubborn dirt, but it also increases the risk of surface damage on softer materials like wood, painted surfaces, and sealants. For most commercial applications, 150-200 BAR is sufficient. Going above 250 BAR is usually only needed for concrete cleaning, paint removal, or pipe unblocking.

Pressure Washer Parameters Explained — BAR, PSI, L/Min, Pumps & Nozzles

1. Pressure (BAR / PSI) — What It Means and How Much You Need

Pressure is the force at which water hits the surface, measured in BAR (metric) or PSI (pounds per square inch, imperial). The conversion is simple: 1 BAR = 14.5 PSI.

A 200 BAR machine delivers 2,900 PSI. A 150 BAR machine delivers 2,175 PSI. Most manufacturers list both values, but it is important to compare the same unit when shopping.

Pressure Range	Duty Level	What It Can Clean	Risk of Damage
80-130 BAR (1,160-1,885 PSI)	Light duty	Cars, patio furniture, light dirt on walls	Low — safe on most surfaces
130-200 BAR (1,885-2,900 PSI)	Medium duty (commercial sweet spot)	Buildings, sidewalks, trucks, equipment	Moderate — use care on soft surfaces
200-280 BAR (2,900-4,060 PSI)	Heavy duty	Concrete, heavy machinery, paint stripping	High — can damage wood, sealant, paint
280-500 BAR (4,060-7,250 PSI)	Ultra high pressure	Pipe unblocking, industrial scale cleaning	Very high — operator training required

Rule of Thumb: For most commercial cleaning applications — building maintenance, vehicle fleets, equipment cleaning — 150-200 BAR is the ideal range. It provides enough power to clean effectively without risking damage to painted or sealed surfaces.

Our BC12GAT (150 BAR, 12 L/Min) and BC25GAT (200 BAR, 15 L/Min) are popular cold water commercial models that cover the most common applications.

2. Flow Rate (L/Min or GPM) — The Second Half of Cleaning Power

While pressure determines how hard water hits the surface, flow rate determines how much water moves across it. Flow is measured in liters per minute (L/Min) or gallons per minute (GPM). 1 GPM ≈ 3.8 L/Min.

Think of pressure as the scrubbing force and flow as the rinsing power. A 200 BAR machine with only 8 L/Min will struggle to clear away the debris it dislodges. A 100 BAR machine with 30 L/Min will flood the area but lack the force to remove stubborn dirt.

Flow Rate	Best For	Cleaning Speed	Water Consumption
8-12 L/Min	Light cleaning, vehicles, small equipment	Moderate	Low — 480-720 L/hr
12-20 L/Min	Commercial buildings, trucks, general use	Good	Medium — 720-1,200 L/hr
20-30 L/Min	Industrial degreasing, heavy machinery	Fast	High — 1,200-1,800 L/hr
30-40 L/Min	Pipe unblocking, large-scale cleaning	Very fast	Very high — 1,800-2,400 L/hr

Hidden Cost: Higher flow rate means faster cleaning but also higher water consumption and larger wastewater disposal requirements. For facilities with limited water supply or strict effluent regulations, choose the lowest flow rate that meets your cleaning needs.

3. Pressure + Flow = Cleaning Units — Finding the Balance

The industry uses a combined metric called Cleaning Units (CU), calculated as: Pressure (PSI) × Flow (GPM) = Cleaning Units. Higher CU means faster cleaning.

Model	Pressure	Flow	Cleaning Units	Best For
BC12GAT	150 BAR / 2,175 PSI	12 L/Min / 3.2 GPM	6,960	Light commercial, property maintenance
BC25GAT	200 BAR / 2,900 PSI	15 L/Min / 4.0 GPM	11,600	Medium commercial, truck fleets
BC17HPGAT	170 BAR / 2,465 PSI	13 L/Min / 3.4 GPM	8,381	Hot water degreasing, food plants
BC20E-TGAT	200 BAR / 2,900 PSI	20 L/Min / 5.3 GPM	15,370	Engine-driven, outdoor/mobile use
BC30DGAT	300 BAR / 4,350 PSI	30 L/Min / 7.9 GPM	34,365	Pipe unblocking, heavy industrial

For most commercial applications, a machine with 8,000-15,000 CU provides a good balance of cleaning speed and cost. Below 5,000 CU, cleaning will be noticeably slow. Above 20,000 CU, you are in heavy industrial territory.

4. Pump Types — Axial vs Plunger Crank

The pump is the heart of any pressure washer. There are two main types used in commercial and industrial machines:

Axial Pump (Cam Pump)

Found on light-duty and residential machines. The pump head is mounted directly on the motor shaft and spins at the same speed as the motor. Axial pumps are cheaper to manufacture but have a shorter lifespan — typically 200-500 hours before seals and valves need replacement. They are suitable for occasional use (up to 2-3 hours per week).

Plunger Crank Pump (Triplex Plunger Pump)

Found on all commercial, industrial, and professional-grade pressure washers. The pump uses a separate crankshaft mechanism driven by a belt or direct coupling. Key advantages:

Lifespan: 1,500-3,000+ hours before major service
Continuous duty: Designed for 8+ hours of daily operation
Higher efficiency: Less energy loss compared to axial pumps
Serviceable: Individual plungers, seals, and valves can be replaced
BIOCCE uses industrial-grade ceramic plunger crank pumps on all commercial models

Pro Tip: If you see a pressure washer advertised as having a "ceramic pump" or "brass pump head," verify whether it is an axial or plunger crank design. Many residential machines advertise ceramic plungers but use an axial pump architecture that cannot handle continuous commercial use.

5. Power Source — Electric kW vs Engine HP

The power source determines where and how the machine can be used, and the power rating (kW or HP) limits the pressure and flow the pump can deliver.

Power Source	Power Rating	Typical Max Pressure	Typical Max Flow	Best For
220V Single Phase	2.2-4.0 kW	150-200 BAR	12-15 L/Min	Indoor, facility cleaning
380V Three Phase	5.5-15 kW	200-350 BAR	15-30 L/Min	Industrial, continuous duty
Gasoline Engine	6-15 HP	200-280 BAR	15-25 L/Min	Outdoor, remote, mobile
Diesel Engine	8-30 HP	200-500 BAR	20-40 L/Min	Pipe unblocking, heavy industrial

Our electric models like the BC12GAT (2.5 kW) and BC25GAT (5.5 kW) run on standard 220V single phase, making them suitable for most commercial facilities. The BC20E-TGAT uses a gasoline engine for outdoor field cleaning, and the BC30DGAT uses a diesel engine for heavy-duty pipe unblocking.

6. Nozzle Types and Their Applications

The nozzle is the single most user-replaceable component that directly affects cleaning performance. Using the wrong nozzle reduces cleaning power or damages surfaces.

Nozzle Orifice Size

The nozzle orifice diameter determines the flow rate. Too small — the pump starves and cavitates (causing internal damage). Too large — the pressure drops and cleaning power is lost.

Flow Rate	Recommended Orifice	Common Nozzle Size
10-15 L/Min	2.0-3.0 mm	#3.0 - #4.0
15-25 L/Min	3.0-4.5 mm	#4.0 - #6.0
25-40 L/Min	4.5-6.0 mm	#6.0 - #8.5

Spray Pattern Nozzles

0° (Jet): Maximum concentrated force. For stubborn blockages, paint stripping. Use with extreme caution — can damage surfaces instantly.
15° (Red): High-force focused stream. For heavy dirt, concrete cleaning, rust removal.
25° (Yellow): Medium-force wide stream. For general cleaning, trucks, equipment, buildings.
40° (White): Wide, low-force fan. For rinsing, light cleaning, windows, delicate surfaces.
65° (Black, low-pressure): Detergent application nozzle. For applying cleaning chemicals without pressure.

Pro Tip: Most commercial cleaning is done effectively with a 25° nozzle at the right pressure. Avoid the temptation to use a 0° jet — it can strip paint, damage sealants, and even etch concrete if held too close.

7. Hot Water vs Cold Water — When Temperature Changes the Equation

Hot water pressure washers add a heating element (heat pump, coil, or boiler) that heats water to 80-155°C. This dramatically improves cleaning on grease, oil, and fat — up to 4x faster than cold water alone.

Parameter	Cold Water	Hot Water (Heat Pump)
Cleaning speed on grease	Baseline	Up to 4x faster
Chemical usage	Full concentration needed	50-70% less detergent
Purchase cost	Lower	30-50% higher
Operating cost	Lower (no heating energy)	Higher (electricity or diesel for heating)
Water temperature	Ambient (10-25°C)	80-155°C adjustable
Ideal applications	Dirt, mud, dust, sand	Grease, oil, fat, wax — kitchens, workshops, food plants

Our BC17HPGAT (170 BAR, 13 L/Min) and BC20HPGAT (200 BAR, 15 L/Min) use heat pump technology for efficient industrial degreasing. For more on choosing between cold and hot water, see our commercial pressure washer buying guide.

Quick Reference: Matching Parameters to Application

Application	Recommended Pressure	Recommended Flow	Suggested Model
Building / warehouse cleaning	150-200 BAR	12-15 L/Min	BC12GAT / BC25GAT
Industrial degreasing (hot water)	170-200 BAR	13-15 L/Min	BC17HPGAT / BC20HPGAT
Municipal / outdoor cleaning	200-270 BAR	15-25 L/Min	BC20E-TGAT / BC27G-TGAT
Sewer / pipe unblocking	200-350 BAR	30-38 L/Min	BC30DGAT
Farm / field cleaning	200-250 BAR	15-20 L/Min	BC350GGAT

Pressure Washer Parameters Explained: Understanding BAR, PSI, L/Min, Pump Types and Nozzles