Blue Spring Pressure Washer Unloader Valve
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- Free Shipping on Orders $149+
- Order by 2pm Pacific, Mon–Thu, and it ships same day. Flat-rate shipping: $8.95 under $50, $12.95 under $149
- FREE local pickup at Oregon City shop
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
| Feature | Details |
|---|---|
| Maximum Flow | 21 GPM |
| Maximum Pressure | 4500 PSI |
| Maximum Temperature | 195°F (continuous use recommended up to 140°F) |
| Inlet Connections | Dual 1/2" FPT |
| Discharge Connection | 1/2" FPT |
| Bypass Connection | 1/2" FPT |
| Connection Type | 1/2" NPT |
| Media | Clean, fresh water |
| Application | Hot or cold water pressure washer systems |
| Pressure Adjustment | Screw-type adjustment knob, adjustable while system running |
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 a family-owned pressure washing equipment shop in Oregon City, OR, run by Tim and Kristina. Before we built equipment, we ran our own pressure washing business for more than ten years — so the parts and chemicals on our shelves are the ones we trust on real jobs.
Our storefront stocks thousands of parts, chemicals and supplies, most in-stock orders ship the same day, and when you call 503-403-6185 you talk to people who have run this gear.
Shipping & Pickup
Orders placed by 2pm Pacific, Monday–Thursday, ship the same day from Oregon City, OR. Orders placed after 2pm on Thursday, or Friday through Sunday, ship the following Monday. Flat-rate shipping is $8.95 on orders under $50 and $12.95 on orders from $50 to $148.99. Orders of $149 or more ship free within the lower 48 states — some large items have their own shipping rate, shown at checkout.
FREE local pickup at our Oregon City shop, Monday–Thursday 8am–4pm.
Returns
Unused items in their original packaging can be returned within 30 days of delivery. A 20% restocking fee applies, and some items — like chemicals and cut-to-length hose — can't be returned. See our Return Policy for details.
