ZH288 Blue Spring Pressure Washer Unloader Valve – 1/2" NPT, 4500 PSI

Upgrade your pressure washer system with the ZH288 Blue Spring Unloader Valve, engineered for high-performance, reliable pressure control. Designed for professional and industrial use, this valve reduces pressure loss, protects your pump, and ensures smooth operation. Easy to install and maintain, it’s ideal for hot or cold water systems up to 4500 PSI.

Key Features:

• Trapped-pressure unloader design for fast, stable pressure regulation
• Reduced pressure loss for maximum system efficiency
• Extremely reliable for continuous-duty applications
• Easy maintenance and adjustment
• Protects pumps by diverting flow when the spray gun is closed

How It Works:

The ZH288 regulates system pressure by controlling bypass flow.

• Gun open: Valve maintains working pressure.
• Gun closed: Water is diverted through the bypass at low pressure, reducing pump stress.
• Zero-pressure mechanism: Keeps delivery and bypass lines connected during shutdown, lowering system pressure evenly.

Installation Guidelines:

• Install upstream of any heat source in hot water systems
• Always use a safety relief valve
• Choose a nozzle that allows at least 5% bypass flow for stable operation
• Bypass water can be returned to the pump intake or to a tank with baffles to reduce turbulence and air bubbles

Pressure Adjustment Tips:

• Adjust with system running and trigger gun open
• Turn adjustment knob to increase/decrease pressure
• If pressure does not rise, check nozzle size vs flow rate
• Replace worn nozzles to restore proper operating pressure
• 🚫 Do not remove the mechanical safety nut—it limits maximum pressure and protects the system

Specifications

Ideal For:

• Commercial and industrial pressure washers
• High-flow pump systems up to 21 GPM
• Hot or cold water cleaning equipment
• Professional cleaning and maintenance operations

About Expert Power Wash

Expert Power Wash is built and operated by Tim and Kristina — a team passionate about giving
pressure washing professionals the best equipment available. Every skid is hand-built in Oregon City, OR, with a focus on quality, reliability, and ease of use in the field.

Our goal is to source 95% of the parts we use from the USA. We distribute across 24 states, Canada, and overseas — backing every unit with a lifetime warranty and personal customer support. We don't just sell equipment; we help you build a successful business with hands-on training and ongoing guidance

Shipping & Pickup

We recommend in-person pickup in Oregon City, OR — this includes a free 2-hour
hands-on training session so you leave confident operating your skid. Transport
shipping is also available and coordinated directly with you.