What Does a Water Blaster Unloader Do? (And Why It Matters)

When it comes to a water blaster’s performance, the pump usually gets the attention. But there’s a smaller component working just as hard behind the scenes: the unloader valve.

It helps control pressure, protects your pump and keeps your water blaster operating as it should. If it isn’t working correctly, you’ll soon know about it.

 

How does an unloader work

• Pull the trigger on your waterblaster and water flows through the hose and out the nozzle
• Release the trigger and the pump keeps running, so the unloader diverts water into a bypass circuit instead of forcing it against a closed gun
• Pull the trigger again, and the unloader switches the water back to the gun. It does this continuously, all day

Most unloaders are pressure-actuated but you can get flow-actuated aswell. These are triggered by the drop in flow instead of pressure. Some systems can also use a regulator instead, which bypasses a small amount continuously rather than dropping to near-idle

Different systems work in slightly different ways, but the goal is the same: control pressure and protect the equipment.

 

Why an unloader isn’t optional

On plunger pumps, like those in UDOR units, a correctly sized unloader is manufacturer-specified as required equipment. Here’s why:

Deadhead condition: running the pump with the discharge closed and no working unloader can quickly damage it

Warranty issue: UDOR treats a missing or incorrect unloader as a warranty condition, not just a safety one

 An important factor is the pressure needs to be measured in the right place. When checking system pressure, take the reading at the pump’s discharge manifold rather than at the gun or nozzle. This gives you an accurate picture of what the pump is actually doing.

 Multi-gun systems need a different setup. If you’re running multiple guns, a standard full-on/full-off unloader isn’t necessarily the right solution. These systems generally require a balance relief valve designed for the application.

 

Brands we fit with UDOR pumps

Most AES Waterblasters fitted with UDOR pumps run a PA or Tecomec unloader:

• PA’s VB35/VB350 unloaders are rated for continuous use up to 60°C, with short-term tolerance to 90°C. PA recommends at least 5% of total flow bypassing continuously to keep pressure steady
• Tecomec’s VRT3 unloaders can include a built-in microswitch to auto-start/stop electric motors with the gun.

Both are quality Italian-made components, matching the EU-sourced parts we build our machines from.

 

Signs your unloader might need attention

A faulty or incorrectly adjusted unloader can show up in several ways:

• Pressure surging or fluctuating during use
• Struggling to reach normal operating pressure
• Pressure staying high after the trigger’s released
• Repeated loading/unloading cycles
• Unusual engine or motor load
• Water leaking at the unloader
• Excessive heat building up while the machine is in bypass

These don’t always mean the unloader is at fault. A worn nozzle, blockage, or pump fault can create similar problems. Correct diagnosis matters more than guessing.

 

A few operating basics that could save you trouble

• Don’t leave your waterblaster sitting in bypass longer than necessary. Water circulating through the pump can heat up quickly. Most pumps shouldn’t see bypass water above roughly 60°C.
• Don’t adjust the unloader to “fix” low pressure without checking the nozzle first.
• Don’t over-tighten the unloader. This means it takes far more pressure to reach bypass than intended and can create a serious safety risk.
• Include the unloader in your regular servicing.

 

The unloader might be a small part of your water blaster, but when you’re relying on that machine to get a job done, it’s an important one.

We’re focused on keeping your equipment working. That means supplying the right gear, but it also means helping you understand it, maintain it and troubleshoot problems when they happen.

If your water blaster is surging, losing pressure or behaving differently when you release the trigger, don’t start changing settings without knowing what’s causing the problem.

Talk to the AES Waterblasters team. We’ll help you find the problem and the right solution to keep you working.