The pressure cleaner's unloader valve functions as a safety device. Unloader valves control the direction of the flow of water exiting the pump. A positive displacement pump always delivers water, regardless of whether the spray gun is open or closed. When the spray gun is closed, the unloader valve redirects the flow of water back to the inlet side of the pump. This prevents the build up of dangerously high pressure and guards against the failure of component parts. Pressure cleaners are installed with either a Trapped Pressure Unloader or a Flow Actuated Unloader.
Spray guns start, stop, and direct the flow of water from the pressure washer’s nozzle. Squeezing the trigger releases pressure. Releasing the trigger interrupts the flow of water to the nozzle, although the pump continues to run. Without an outlet for releasing this water, pressure would continue to build. A very dangerous situation would result.
The Unloader Valve
Unloader valves function as “traffic cops” and pressure regulator that direct the flow of water in a pressure cleaner system. When water stops flowing from the nozzle of a spray gun, the unloader valve redirects it for a safe pressure outlet. When the cleaner is in “bypass mode,” water that is not released by the spray gun is diverted back to the inlet side of the pressure pump. It then circulates through the pump and back to the inlet side of the unloader valve. Water is once again either released via the spray gun, or redirected to the pump. The process of continued re-cycling of water through the pump is called “cycling.”
- “Trapped Pressure” unloader valves are the most commonly used. These valves sense and are activated by building pressure at the pump output. Trapped Pressure valves initiate bypass mode in direct response to building pressure in the hose between the pump output and the spray gun. They are often simply called “Pressure” valves. A spike of pressure results when cycling is interrupted and Trapped Pressure valves re-release water to the spray gun. Operators should be prepared for the “kickback” effect on the spray gun or wand to avoid loss of control or injury.
- “Flow Actuated” unloader valves respond to the interruption of water flow to the nozzle. These valves sense any decrease in flow from the valve to the spray gun and initiate the bypass loop in response. Unlike Trapped Pressure valves, no pressure is trapped, so no “kick back” occurs when water is re-released. With Flow Actuated unloader valves, operators cannot regulate pressure by downsizing the orifice size of nozzles. Flow Actuated valves detect the loss in flow, and react by cycling repeatedly.
Although cycling prevents the dangerous buildup of pressure, added safety concerns arise during bypass mode. Moving parts in the pump create friction and heat which is transferred to the water flow in bypass. Cycling water can quickly be heated to dangerous temperatures as no cool water enters the pump during bypass.
Most pressure cleaner pumps can withstand temperatures of 140º F. At higher temperatures, damage to the pump can occur. Pump packings, plungers, seals, and even the short bypass hose in external bypass systems may be damaged. Thermal Relief Valves offer some protection against excessive heat buildup. They ensure cool water is released to the pump when temperatures exceed 145º F.
Operators are advised to always take care to prevent overheating regardless of the presence of Thermal Relief valves. Pumps should not be allowed to operate in bypass mode for more than 2 to 3 minutes. Squeezing the spray gun trigger always interrupts cycling and introduces new, cool water to the system.
Safety Relief Valve
The safety relief valve is the designed weak point in the pressure washer. If the unloader malfunctions, the safety relief valve will open and relieve system pressure safely.
EZ Start Adjustable Unloader
EZ Start unloader eliminates pressure in the pump while starting the engine making the unit to start easier; less damaging to starter motors especially on electric start engines.
Pressure Regulator - Unloader |
AL607 Unloader
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Arrowline Unloader, ideal for replacement of any type of pressure regulator, it is inexpensive and problem free.
- Maximum Rating: 4,200 PSI at 7.8 GPM, 190°F
- Inlet/Outlet: 3/8" FNPT
- Bypass: 3/8" FNPT
- Weight: 2.1 lbs
Ordering Information - FREE SHIPPING
MODEL |
DESCRIPTION |
PRICE |
BE-AL607 |
Unloader Valve AL607 |
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BE-AL607EZ* |
Unloader Valve with E-Z Start |
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* EZ Start unloader eliminates pressure in the pump while starting the engine making the unit to start easier; less damaging to starter motors especially on electric start engines.
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Unloader
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- Maximum Rating: 3,600 PSI at 8 GPM, 200°F
- Inlet/Outlet: 3/8" MNPT
- Bypass: 1/4" FNPT
- Weight: 1.65 lbs
Ordering Information - FREE SHIPPING
MODEL |
DESCRIPTION |
PRICE |
BE-85-300-001 |
Unloader Valve MV550 |
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This unloader comes with the EX Start feature.
- Maximum Rating: 3,600 PSI at 8 GPM, 195°F
- Inlet/Outlet: 3/8" MNPT
- Bypass: 3/8" FNPT
- Weight: 2 lbs
Ordering Information - FREE SHIPPING
MODEL |
DESCRIPTION |
PRICE |
BE-85-300-206 |
Unloader Valve with EZ Start |
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This unloader comes with the EZ Start feature.
- Maximum Rating: 4,500 PSI at 8 GPM, 195°F
- Inlet/Outlet: 3/8" MNPT
- Bypass: 3/8" FNPT
- Weight: 1.95 lbs
Ordering Information - FREE SHIPPING
MODEL |
DESCRIPTION |
PRICE |
BE-85-300-212 |
Unloader Valve with EZ Start |
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MV595
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This unloader comes with built-in thermal valve and safety relief valve.
- Maximum Rating: 4,000 PSI at 8 GPM, 145°F
- Inlet/Outlet: 3/8" MNPT
- Bypass: 1/4" FNPT
- Weight: 2.4 lbs
Ordering Information - FREE SHIPPING
MODEL |
DESCRIPTION |
PRICE |
BE-85-300-012 |
Unloader Valve MV595 |
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VB7 Regulator - Unloader
Fits CAT 4SF pumps and other pumps; 7.8 GPM – 3600 PSI max pressure
- Rated pressure: 3200 PSI
- 200° F
- 3/8" MPT inlet, 1/4" FPT gauge port
- 3/8" FPT outlet & bypass
- 19.7 oz weight
(Shipping charge of $6.50 will apply on this item if the total order is less than $45.00)
MODEL |
DESCRIPTION | PRICE |
SM-8-712-741-0 | w/o Knob | |
SM-8-904-580-0 | w/ Knob | |
SM-8-704-488-0 | Repair Kit | |
SM-8-712-735-0 | Knob Only | |
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High GPM Unloader |
VB80 Unloader
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To be used up to 21 GPM.
- Maximum Rating: 4,000 PSI at 21 GPM, 180°F
- Inlet/Outlet: 1/2" FNPT
- Bypass: 1/2 " FNPT
- Weight: 3.05 lbs
Ordering Information - FREE SHIPPING
MODEL |
DESCRIPTION |
PRICE |
BE-85-310-003 |
Unloader Valve VB80 |
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Stainless Steel Unloader Valves |
Stainless Steel Unloader Valve |
Stainless Steel Unloader Valve
- PSI 2900 or 3650
- Max GPM: 7.8
- Inlet: 3/8" F
- Outlet: 3/8" F
- By-Pass: 1/4" F
- Max Temp: 190° F
MODEL |
DESCRIPTION |
PRICE |
AR-AL635 |
VX S.S. 303 - Unloader Valve 2900 PSI |
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AR-AL636 |
VX S.S. 303 - Unloader Valve 3650 PSI |
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Stainless Steel Unloader Valve |
Stainless Steel Unloader Valve
- Max GPM: 12
- Inlet: 3/8" F
- Outlet: 3/8" M
- By-Pass: 1/4" F
- Max Temp: 195° F
MODEL |
DESCRIPTION |
PRICE |
AR-AR21350 |
VR S.S. 316 - Unloader Valve 2900 PSI |
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Stainless Steel Unloader Valve |
Stainless Steel Unloader Valve
- PSI 2900 or 3650
- Max GPM: 7.8
- Inlet: 3/8" F
- Outlet: 3/8" F
- By-Pass: 1/4" F
- Max Temp: 190° F
MODEL |
DESCRIPTION |
PRICE |
AR-AL637 |
VX S.S. 316 - Unloader Valve 2900 PSI |
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AR-AL638 |
VX S.S. 316 - Unloader Valve 3650 PSI |
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Unloader Valves with Pressure Switch |
VRL Unloader Valve |
VRL Unloader Valve with Pressure Switch
- Max GPM: 8
- Inlet: 3/8" F
- Outlet: 3/8" F
- By-Pass: 3/8" F
- Max Temp: 190° F
- Knob: Yes
MODEL |
DESCRIPTION |
PRICE |
AR-AL684 |
VRL Unloader Valve with Pressure Switch 2900 PSI |
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AR-AL685 |
VRL Unloader Valve with Pressure Switch 3650 PSI |
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 VRT Unloader Valve |
VRT Unloader Valve with Pressure Switch
- PSI 3650 or 4200
- Max GPM: 7.8
- Inlet: 3/8" F
- Outlet: 3/8" F
- By-Pass: 2 x 3/8" F
- Max Temp: 190° F
- Knob: Yes
MODEL |
DESCRIPTION |
PRICE |
AR-AL686 |
VRT Unloader Valve with Pressure Switch 3650 PSI |
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AR-AL687 |
VRT Unloader Valve with Pressure Switch 4200 PSI |
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Pulsar Unloader Valve |
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Pulsar Unloader Valve
- Pulsar 3 blue rated 3200 PSI - Max 3650 PSI
- 8 GPM
- All stainless steel valves
- Pulsar 3 white rated 1400 PSI -Max 1750 PSI
- Pressure actuated
- Forged body
- Pulsar 280 HP rated 4050 PSI - Max 4350 PSI
- 3/8" FPT inlet, outlet
- 195° F
- Two 3/8" FPT bypass ports
(Shipping charge of $6.50 will apply on this item if the total order is less than $45.00)
MODEL |
DESCRIPTION | PRICE |
SM-8-712-650-0 | Pulsar 3 (Blue) w/ Knob | |
SM-8-712-651-0 | Pulsar 3 (Blue) w/o Knob | |
SM-8-712-653-0 | Pulsar 3 (White) w/ Knob | |
SM-8-712-731-0 | Pulsar 280 HP | |
SM-8-704-462-0 | Repair Kit – Pulsar 3 | |
SM-9-802-004-0 | Repair Kit – 280 HP | |
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See Also |
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Inlet Water Filter
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Water Filters
From: $21.90
Protects the system from contaminants in the water |
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Large Water Broom
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Water Brooms
From: $44.98
High pressure water brooms are powerful, reliable and universal in pressure washing driveways, boat decks, flat surfaces and more. Used to clean flat surfaces quickly, easily and evenly. |
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