Cut Through Clogs: A Smarter Approach to Wastewater Grinding with the Wilo-Rexa PRO-S

10.26.2026

How double-shear maceration, optimized hydraulics, and robust construction help improve reliability in pressure sewer applications

Wastewater pumping has never been an easy job.

Municipal and commercial wastewater systems must handle fibrous materials, solids, debris, and increasingly challenging wastewater conditions. In pressure sewer applications, these challenges are compounded by smaller discharge piping and high static heads, making reliable solids reduction one of the most important considerations when selecting a grinder pump.

The Wilo-Rexa PRO-S was developed specifically for these demanding applications.

It combines a radial macerator with a double-shear effect, optimized hydraulics, and a robust submersible motor design to provide reliable pressure drainage in commercial and municipal wastewater systems. It also excels with reduced installation costs through compatibility with smaller piping as one of the platform's core advantages.

The Challenge: Keeping Wastewater Moving

Clogging is more than an inconvenience.

Fibrous material and other solids entering a wastewater pump can restrict the pump inlet, interfere with the impeller, and ultimately increase maintenance demands and downtime.

Grinder pumps address this challenge by reducing solids before they continue through the pressure sewer system. But not all cutting systems approach the job the same way.

Some grinder designs rely on a single cutting stage. The Wilo-Rexa PRO-S takes a different approach.

Two Cutting Actions. One Robust Macerator.

At the heart of the Wilo-Rexa PRO-S is its radial macerator with a double-shear effect.

Instead of relying on only one cutting mechanism, the design combines external and internal cutting action. Material is reduced before and as it passes through the hydraulic system, helping the pump manage difficult solids and fibrous wastewater more reliably.

Wilo's technical material specifies a cutter made from hardened stainless cutting steel with a hardness of 59 HRC, with an average chopping result of approximately 0.4 inches depending on the type of solids and flow behavior.

This approach is designed to reduce the likelihood that difficult material reaches the hydraulic components intact.

The cutting assembly is also replaceable, allowing the grinder components to be serviced without replacing the complete hydraulic assembly.

Why Double-Shear Matters

For operators, the principle is straightforward:

Reduce difficult solids before they become a pumping problem.

The external cutting stage addresses material entering the pump, while the additional cutting action further reduces the material as it moves through the pump.

More Than a Grinder: Optimized Hydraulics

Cutting solids effectively is only part of the equation.

Once material has been reduced, the pump still has to move wastewater efficiently against the required system head.

The Wilo-Rexa PRO-S combines its macerator with optimized hydraulics designed for high delivery heads while maintaining efficient operation. Wilo specifically identifies the optimized combination of hydraulics and macerator as a key contributor to maximum delivery head and improved efficiency.

That combination makes the PRO-S particularly well suited for pressure sewer applications where elevations, long force mains, or system losses create demanding operating conditions.

Designed Around the Needs of the U.S. Market

For engineers and operators, hydraulic performance is only part of pump selection. Mechanical configuration, electrical options, monitoring, and approvals can be equally important.

The Wilo-Rexa PRO-S addresses these requirements with a configuration designed for U.S. wastewater applications.

Standard U.S. configurations include a 1½-inch, 125-pound ANSI discharge flange, FM approval, two mechanical seals, and seal chamber monitoring. The range supports 230 V single-phase as well as 230 V and 460 V three-phase configurations, depending on pump size.

The expanded portfolio extends the available motor range to approximately 16.1 HP, significantly broadening the performance range of the PRO-S platform.

Key Features

• Radial macerator with double-shear effect
• External and internal cutting action
• Hardened stainless cutting steel
• Optimized hydraulic design
• Two mechanical seals
• Seal chamber monitoring
• 1½-inch, 125-pound ANSI discharge flange
• FM approval as standard
• Motor options up to 16.1 HP

How Does the Wilo-Rexa PRO-S Compare?

Many grinder pumps such as the Liberty Pump LGH and LGV Series or the Myers WG(X) Series can move wastewater through small-diameter pressure sewer systems. The differences become clearer when looking at how the pump handles solids, protects the motor, connects to the piping system, and accommodates demanding duty points.

A Different Approach to Grinder Pump Design

A grinder pump operates in an environment where reliability depends on more than just the cutter.

The Wilo-Rexa PRO-S uses a robust motor construction together with two mechanical seals and seal chamber monitoring. Wilo positions these features as part of the pump's strategy for long service life and operational reliability.

FM approval is included in the U.S. configuration as standard, providing an important consideration for applications requiring equipment approved for the applicable hazardous-location installation.

Smaller Piping Can Mean More Than a Smaller Pump

Pressure sewer projects need to be evaluated as complete systems.

Pump efficiency matters, but so do pipe diameter, fittings, installation effort, and the ability to generate sufficient head for the application.

The Wilo-Rexa PRO-S is designed for connection to small-diameter piping, which Wilo identifies as an opportunity to reduce overall installation costs.

This is an important distinction when evaluating a grinder pump. The lowest pump purchase price does not necessarily result in the lowest installed system cost.

From 1.5 HP to Demanding High-Head Applications

The expanded Wilo-Rexa PRO-S portfolio gives engineers greater flexibility when designing pressure sewer systems.

Earlier U.S. configurations included up to 5.2 HP motors. The expanded product range now extends the platform to approximately 16.1 HP, allowing the same basic grinder-pump concept to address significantly more demanding applications.

That expanded range can simplify pump selection for designers who want the double-shear macerator concept across multiple pressure sewer duty points.

A Different Approach to Grinder Pump Design

The Wilo-Rexa PRO-S brings together several features that are often considered separately when evaluating a grinder pump:

• Solids handling: double-shear radial macerator
• Hydraulic performance: optimized pump hydraulics for demanding heads
• Reliability: two mechanical seals and seal chamber monitoring
• Installation: compact 1½-inch ANSI discharge connection
• Safety: FM approval as standard
• Application range: motor options extending to 16.1 HP

For municipal operators, consulting engineers, contractors, and commercial wastewater professionals, the result is a submersible grinder pump designed around a simple objective:

Cut the solids. Keep the wastewater moving.