Top OEMs for Submersible Pumps in Water & Wastewater Applications

Introduction to Submersible Pump Specification in Municipal and Industrial Systems

The submersible solids-handling pump represents the backbone of modern municipal wastewater collection systems, storm water management, and industrial effluent transport. Unlike dry-pit configurations where the prime mover is separated from the hydraulic fluid, the submersible pump integrates the motor and hydraulic end into a single, hermetically sealed unit designed to operate completely submerged in the process fluid.

For consulting engineers, plant managers, and utility directors, the specification of these units involves a complex balance of hydraulic efficiency, solids-passage capability, material longevity, and total cost of ownership (TCO). These pumps are frequently deployed in hostile environments—such as raw sewage lift stations, influent headworks, sludge thickening processes, and storm water retention basins—where failure results in sanitary sewer overflows (SSOs), regulatory fines, and immediate public health hazards.

The “commoditization” of pumps in smaller horsepower ranges often obscures the significant engineering differences between Original Equipment Manufacturers (OEMs). While hydraulic curves may appear similar on paper, the internal engineering regarding mechanical seal protection, cable entry systems, bearing life (L10h), and motor insulation classes varies drastically.

Furthermore, the rise of “flushable” wipes and increased ragging content in modern wastewater has shifted the design priority from pure hydraulic efficiency to non-clogging reliability. An OEM’s ability to handle stringy solids without derating performance is now a primary selection factor. This article provides an engineer-centric, impartial analysis of the leading OEMs in the submersible pump market, focusing on the technical merits and application fit for Flygt (Xylem), Grundfos, KSB, Sulzer, Tsurumi, Fairbanks Nijhuis (Pentair), and Wilo.

Engineering Criteria for Submersible Pump Selection

Selecting a submersible pump extends beyond identifying the Best Efficiency Point (BEP) on a curve. The selection process must account for the unique stressors of submerged operation, including heat dissipation, seal integrity, and variable inflow conditions.

1. Hydraulic Performance and Impeller Geometry

The geometry of the impeller dictates the pump’s ability to balance efficiency with solids handling.

• Channel Impellers (Single/Multi-Vane): Traditionally offer high efficiency but are prone to leading-edge ragging. Modern designs incorporate backswept leading edges to shed solids.
• Vortex (Recessed) Impellers: Create a hydraulic vortex where the fluid does not pass through the impeller vanes. This drastically reduces clogging risk and handles abrasive solids better, but typically at a 10–20% efficiency penalty compared to channel impellers.
• Screw Centrifugal Impellers: Offer a hybrid approach with high efficiency and excellent gentleness for handling sludge or shear-sensitive flocs, though they can be physically larger.
• Chopper/Grinder Hydraulics: Essential for low-flow, high-head applications (like pressure sewer systems) where velocity is insufficient to scour lines, but generally avoided in large lift stations due to maintenance intensity and energy costs.

2. Solids Handling and the “Ragging” Phenomenon

The definition of “solids handling” has evolved. Historically, passing a 3-inch spherical solid was the standard specification (Ten States Standards). However, modern waste streams contain high volumes of synthetic fibers that form “ropes” rather than spheres. Engineers should evaluate OEMs based on adaptive hydraulics—impellers that can move axially to allow debris to pass or those with hardened cutting edges that actively clear the volute tongue.

3. Materials of Construction and Metallurgy

Standard ASTM A48 Class 30 cast iron is sufficient for neutral domestic sewage. However, specific environments require upgraded metallurgy:

• Duplex and Super Duplex Stainless Steel (CD4MCu): Required for corrosive industrial effluents, high H2S environments, or septic sludge.
• High Chrome Iron (ASTM A532): Mandatory for grit chambers, stormwater containing road sand, or abrasive slurry applications to prevent rapid volute erosion.
• Ceramic Coatings: Some OEMs offer internal ceramic epoxy coatings to smooth flow paths and resist abrasion, though these can be prone to delamination if not factory-applied correctly.

4. Motor Protection and Sealing Systems

The most common failure mode for submersible pumps is moisture intrusion.

• Cable Entry: The cable entry point must be hermetically sealed. Top OEMs utilize a separated terminal board with a resin-potted chamber to prevent capillary action (wicking) of water down the cable leads into the stator if the cable jacket is cut.
• Mechanical Seals: A dual mechanical seal arrangement is the industry standard. The preferred configuration is tandem seals (independent springs) operating in an oil chamber. Materials like Silicon Carbide vs. Silicon Carbide (SiC/SiC) are preferred for the lower (process-side) seal for maximum abrasion resistance.
• Monitoring: Specifications should mandate moisture detection probes (in the oil chamber and stator housing) and thermal switches in the motor windings.

5. Thermal Management and VFD Operation

Submersible motors rely on the surrounding fluid for cooling. When operated on Variable Frequency Drives (VFDs), the motor speed decreases, potentially reducing the cooling flow. Furthermore, pumps operating in “snore” conditions (partially submerged) risk overheating. Engineers should specify cooling jackets (closed-loop glycol or process media cooling) for dry-pit submersible installs or applications where the liquid level may drop below the stator housing. Insulation Class H (180°C) is preferred over Class F (155°C) for VFD applications to withstand higher thermal stresses.

OEM Comparison Matrix: Submersible Wastewater Pumps

The following table analyzes the seven specified OEMs based on their typical market positioning, technical strengths, and operational considerations. This data is derived from general industry experience and published technical capabilities.

OEM	Typical Applications	Technical Strengths	Best-Fit Scenarios	Maint. Considerations
Flygt (Xylem)	Municipal Lift Stations, Headworks, Stormwater	N-Technology (self-cleaning impellers), integrated intelligence (Concertor), massive install base.	Standardization across large municipalities; severe ragging environments.	Proprietary parts can be costly; restrictive guide rail compatibility.
Grundfos	Municipal Collection, Lift Stations, Industrial Treatment	S-Tube impeller design, high wire-to-water efficiency, SE/SL range motor efficiency (IE3/IE4).	Projects prioritizing energy efficiency and advanced controls integration.	Controls often require proprietary dedicated user interfaces.
KSB	Heavy Industrial, Deep Tunnels, Large Municipal	Amarex line robustness, resin-potted cable entries, long bearing life designs.	Heavy-duty applications, grit chambers, and industrial wastewater with high reliability needs.	Can be heavier/larger footprint for equivalent HP due to conservative safety factors.
Sulzer	Main Pumping Stations, Stormwater, High-Head	Contra-Block system, Premium Efficiency motors, strong history in large axial flow subs.	High-head lift stations and large stormwater retention requiring mixed-flow hydraulics.	Legacy ABS product lines may have different spare part supply chains.
Tsurumi	Construction Dewatering, Small Muni, Industrial Sump	Air-filled motors (lightweight), potting of cable entry, high-chrome wear parts standard on many lines.	Abrasive environments, contractor-managed systems, decentralized small lift stations.	Less common in massive dry-pit submersible muni specs; focused on wet-pit.
Fairbanks Nijhuis	Municipal Solids Handling, RAS/WAS Pumping	Bifold/Mono-port impellers, strong US municipal customization, Chopper options.	Applications requiring heavy solids passing capability and custom casting materials.	Lead times can vary for highly customized US-manufactured units.
Wilo	Municipal, Building Services, Industrial	Ceram coatings, efficient cooling systems, SOLID impeller technology.	Modern treatment plants looking for long lifecycle coatings and high-tech monitoring.	Market penetration in US muni sector is growing but historically lower than Flygt/KSB.

In-Depth Analysis of Top OEMs

The following analysis details the engineering philosophy and product capability of the locked list of manufacturers for the Submersible Pump category.

Flygt (Xylem)

Engineering Philosophy: Flygt, a brand of Xylem, is arguably the most recognized name in the submersible wastewater industry. Their engineering philosophy centers on hydraulic innovation to solve operational problems, specifically clogging. They pioneered the submersible motor concept in the mid-20th century and have maintained market dominance through continuous R&D.

Technical Highlight: N-Technology. The core of Flygt’s modern specification is the N-impeller. Unlike standard channel impellers, the N-impeller features a backswept leading edge and a relief groove in the volute. As solids land on the leading edge, they slide backward toward the periphery and are discharged, rather than accumulating. For chronic ragging issues, the “Adaptive N” allows the impeller to move axially upward to pass large debris, then return to its operating position.

Operational Context: Flygt pumps are often the default specification for municipal lift stations. Their “Concertor” line represents the new wave of “intelligent pumping,” integrating the VFD, pump controller, and motor into the submersible head. This reduces panel complexity but locks the utility into a proprietary ecosystem. Engineers must weigh the benefits of integrated intelligence against the limitations of single-source servicing.

Grundfos

Engineering Philosophy: Grundfos approaches the market with a focus on motor efficiency and intelligent controls. While they have a massive presence in clean water, their wastewater division (S-Series, SE/SL ranges) is engineered with a focus on wire-to-water efficiency and smooth hydraulic passages.

Technical Highlight: S-Tube Impeller. The S-Tube is a tube impeller design that eliminates edges where rags can catch. It essentially extends the pipework through the pump. This design maintains high hydraulic efficiency while providing free passage for solids comparable to the discharge diameter. Furthermore, Grundfos places heavy emphasis on IE3 and IE4 motor efficiencies, making them a strong candidate for projects with strict energy consumption mandates (Green Bond funded projects, for example).

Operational Context: Grundfos units are favored in treatment plants where SCADA integration is critical. Their dedicated controllers (MP 204) provide deep data granularity regarding motor health, phase imbalance, and power consumption. The trade-off is often a requirement to use Grundfos-specific monitoring relays to unlock the full diagnostic potential.

KSB

Engineering Philosophy: KSB represents traditional German heavy engineering. Their pumps are characterized by robust castings, stiff shafts (low deflection), and conservative safety factors. KSB often targets the most difficult applications, including deep tunnel systems and combined sewer overflows (CSO).

Technical Highlight: Cable Entry and Sealing. KSB’s Amarex line addresses the Achilles’ heel of submersibles: water intrusion. Their design typically includes a longitudinally watertight cable entry. If the cable jacket is damaged, water cannot travel down the strands into the motor. Additionally, their mechanical seals are often housed in a large oil reservoir designed to allow for extended maintenance intervals.

Operational Context: KSB is a strong fit for “critical” lift stations—those receiving large influent flows where failure is not an option. They are also prominent in the industrial sector. Their hydraulic designs, while efficient, prioritize non-overloading power curves and stable operation across the full H-Q curve over peak efficiency at a single point.

Sulzer

Engineering Philosophy: Sulzer has consolidated several legacy brands (most notably ABS and Paco) into a comprehensive submersible offering. Their focus is on handling difficult solids and high-head applications. The XFP series is their flagship municipal wastewater pump.

Technical Highlight: Contra-Block and Premium Efficiency. Sulzer markets the “Contra-Block” system (an ABS legacy), which includes a shredding function at the inlet to break down solids before they enter the impeller vane, differing from the “pass-through” philosophy of the S-Tube. Sulzer was also an early adopter of IE3 equivalent motors in the submersible submersible market, pushing for lower operational carbon footprints.

Operational Context: Sulzer is highly adaptable. They offer a wide range of wet-well and dry-well submersible options. They are particularly strong in large axial flow and mixed flow pumps for stormwater and flood control applications, where moving massive volumes of water at low head is the primary requirement.

Tsurumi

Engineering Philosophy: Tsurumi follows a different design philosophy than the European giants (Flygt/KSB/Grundfos). Originating from a construction and dewatering background, their sewage pumps are built for abuse. They often utilize air-filled motors rather than oil-filled, making them lighter and easier to service in the field.

Technical Highlight: Anti-Wicking Block and Oil Lifter. Tsurumi’s patented “Oil Lifter” is a simple mechanical device inside the oil chamber that lubricates the mechanical seal faces even when the oil level is low. This provides a fail-safe against poor maintenance. Their cable entry features a distinct anti-wicking block that physically separates the cable conductors from the motor chamber.

Operational Context: While Tsurumi is less frequently specified for massive 500HP+ municipal influent pumps, they are a dominant force in smaller lift stations, package plants, and industrial sumps. Their “C-Series” cutter pumps are extremely effective in apartment complexes or commercial developments prone to ragging. They are often viewed as the “operator’s pump” due to simplicity and stock availability.

Fairbanks Nijhuis (Pentair)

Engineering Philosophy: Fairbanks Nijhuis (part of Pentair) holds a legacy position in the North American municipal market. Their engineering focuses on customization and broad hydraulic coverage. Unlike some OEMs that push a specific impeller style, Fairbanks offers a wide variety of hydraulic ends including recessed, mono-port, and chopper designs.

Technical Highlight: Solids Handling Versatility. Fairbanks is well-regarded for their single-vane and dual-vane (Bifold) solids handling impellers. They maintain robust domestic casting capabilities, allowing for custom metallurgy specifications (such as CD4MCu) more readily than some import-only competitors. Their pumps are often designed to match existing competitor footprints, making them a strong player in the retrofit market.

Operational Context: Fairbanks is a strong fit for municipalities that require “Buy American” compliance or have unique piping configurations requiring custom volute discharge orientations. Their pumps are heavy, durable, and designed for long-term municipal asset management plans.

Wilo

Engineering Philosophy: Wilo competes directly with the top-tier European manufacturers, emphasizing precision engineering and advanced coatings. Their approach combines hydraulic efficiency with material science to extend the Mean Time Between Failures (MTBF).

Technical Highlight: Ceram Coatings and SOLID Impellers. Wilo promotes the use of “Ceram” coatings—internally applied industrial coatings that reduce friction losses and protect against abrasion and corrosion. Their SOLID impeller technology is designed to manage untreated sewage with high rag content, utilizing a geometry that balances free passage with hydraulic balance to reduce vibration.

Operational Context: Wilo is an excellent fit for modern, energy-conscious treatment plants. Their “Rexa” series offers a competitive alternative to Flygt and KSB. While their install base in the US is smaller than Xylem, their technical support and product quality are considered top-tier. They are often specified in applications where long-term energy modeling is a deciding factor in the bid process.

Application Fit: Matching OEM to Scenario

No single OEM is the superior choice for every application. The “best” pump depends entirely on the fluid characteristics and the installation constraints.

Municipal Wastewater (Lift Stations)

For standard raw sewage lift stations, Flygt and Grundfos are the market leaders. Flygt’s N-impeller is generally preferred where historical data shows high ragging frequency. Grundfos is preferred where energy efficiency rebates or strict OPEX limits are in place. Fairbanks Nijhuis is a strong contender here for municipalities requiring domestic manufacturing compliance.

Industrial Wastewater & High Abrasives

When the fluid contains grit, sand, or industrial byproducts, KSB and Tsurumi excel. Tsurumi’s use of high-chrome impellers as a standard in many lines makes them cost-effective for abrasive sumps. KSB’s heavy-duty bearing arrangements are better suited for the high radial loads caused by pumping slurries or uneven flows.

Stormwater and Flood Control

Sulzer and KSB are dominant in high-flow, low-head applications. Their axial and mixed-flow submersible columns are engineered to move massive amounts of water efficiently. Flygt also competes heavily here with their PL (propeller) series, but Sulzer’s legacy with ABS gives them a very strong portfolio for large-scale stormwater management.

Small Diameter / Grinder Applications

For low-flow pressure sewer systems or commercial pads, Tsurumi (C-Series) and Flygt (M-Series) are the logical choices. Tsurumi offers a rugged, cost-effective cutter pump that is easy to replace, while Flygt offers a more sophisticated grinder unit suited for larger networks.

Critical Considerations for Engineers and Operators

1. The “Or Equal” Trap

Engineers must be cautious with “Or Equal” clauses. A pump with the same flow and head does not necessarily have the same solids handling capability or motor service factor. When specifying, it is critical to mandate the minimum sphere pass diameter and the motor insulation class (Class H is superior to F). If a specific anti-clogging technology (like a backswept impeller) is required, it should be written into the performance specification, not just the brand list.

2. Guide Rail Compatibility

One of the biggest hurdles in retrofitting pumps is the guide rail system. Flygt pumps generally require Flygt discharge bases and rails. However, many competitors (like Fairbanks Nijhuis and Tsurumi) offer “adapter claws” or sliding brackets that allow their pumps to mount onto existing Flygt, ABS, or equivalent rail systems without draining the wet well to replace the base elbow. This is a critical maintenance consideration for older lift stations.

3. Proprietary vs. Open Architecture

The trend toward “Smart Pumps” (integrated VFDs and controllers on the pump head) simplifies installation but complicates long-term maintenance. If a “Smart Pump” fails, the operator cannot simply bypass the VFD and run the pump across the line; the entire unit must be pulled. Operators should decide if they prefer the intelligence to be in the panel (accessible, replaceable components) or on the pump (proprietary, submerged).

4. Cable Management

Cable failure accounts for a significant percentage of submersible pump issues. Engineers should specify stainless steel strain relief grips (Kellems grips) to ensure the weight of the cable does not pull on the gland entry. Furthermore, standardizing on cable lengths (e.g., specifying 50ft leads for all pumps regardless of depth) allows for easier inventory management and flexibility in moving pumps between stations.

Conclusion

The selection of a submersible pump OEM for water and wastewater applications is a decision that dictates the operational reliability of the facility for the next 15 to 20 years.

Flygt remains the benchmark for municipal standardization and anti-clogging technology. Grundfos offers superior efficiency and controls integration. KSB and Sulzer provide the heavy-duty engineering required for critical, high-volume, or deep-install applications. Tsurumi offers unmatched durability and simplicity for abrasive or contractor-driven environments, while Fairbanks Nijhuis provides customization and domestic support. Wilo serves as a high-tech alternative with a focus on coatings and long-term surface protection.

For the consulting engineer and the plant manager, the goal is to align the specific pain points of the application—be it ragging, abrasion, energy costs, or maintenance accessibility—with the specific engineering philosophy of the OEM. A lower capital cost at the bid tab usually evaporates after the first unscheduled pull-and-clean event. Specification should always prioritize hydraulic reliability and mechanical robustness over initial purchase price.

source https://www.waterandwastewater.com/top-oems-for-submersible-pumps-in-water-wastewater-applications/