Civil wastewater: how to choose between submersible pumps and grinder pumps
Flow rate, wastewater type and head as the key selection criteria
In civil wastewater handling, the choice of pumping technology is never neutral. Inaccurate sizing or selecting a pump that does not match the application leads to clogging, repeated warranty claims, dissatisfied end users and reduced margins for both installers and distributors.
For this reason, when designing or retrofitting drainage systems in residential buildings, restaurants and light industrial applications, it is essential to clearly distinguish between conventional submersible pumps and grinder pumps. Lowara supports this choice with a product range engineered to cover every application scenario.
The three key selection parameters
1. Required flow rate (Q)
Flow rate determines the hydraulic sizing of the pump and must be calculated based on the number of connected fixtures, simultaneous use and any peak discharge conditions.
Lowara DN series submersible pumps, featuring an open impeller with abrasion-resistant rubber coating, are suitable for drainage applications involving clean or slightly dirty water with a limited presence of suspended solids.
2. Type of wastewater
The nature of the fluid is the main factor in pump selection.
For standard domestic wastewater, Lowara DOMO submersible pumps, in the versions suitable for the specific application, provide adequate free passage and ease of maintenance; the Lowara DN series, on the other hand, is specifically designed for draining clean or slightly dirty water.
Where the wastewater contains fibres, paper, stringy materials or where there is a real risk of foreign objects entering the system — as is often the case in restaurants, public facilities and small workshops — the correct choice is the Lowara DOMO GRI series with integrated grinder system. The grinder shreds solids before they enter the discharge line, preventing blockages even in small-diameter pipework.
A grinder is not a universal solution. It is a targeted technical choice to be adopted when there is a high risk of clogging or where the system is constrained by limited pipe diameter.
3. Total head (H)
Total head — geodetic head plus friction losses — directly affects pump curve selection. Where high risers are required or wastewater must be lifted from below sewer level, the actual duty point must always be verified.
In systems using Lowara DOMO GRI grinder pumps, the ability to operate with small-diameter pipework significantly simplifies installation in refurbishment projects or basement applications, reducing installation time and ancillary costs.
Typical applications and recommended Lowara solutions
Residential buildings and apartment blocks
Predominantly domestic wastewater, high service continuity and long-term reliability are the main requirements.
The reference solution is the Lowara DOMO family, in the versions best suited to the specific wastewater type; the Lowara DN series, on the other hand, is designed for drainage applications involving clean or slightly dirty water, with the added benefit of simplified maintenance.
Restaurants and public facilities
These applications involve a greater presence of fibres and undissolved materials, a higher risk of misuse and often compact installations with structural constraints.
In these applications, the Lowara DOMO GRI series — the grinder-equipped version of the DOMO family — is the most effective technical solution whenever solids need to be shredded and wastewater conveyed through small-diameter pipework, dramatically reducing post-installation service calls.
Light industry and small workshops
Wastewater characteristics may vary, with the possible presence of larger solid particles and a greater need for mechanical robustness.
In these applications, Lowara DN or DL pumps equipped with vortex or single-channel impellers provide the required flexibility. A vortex impeller reduces the risk of clogging, while a single-channel impeller is better suited to handling larger solids. Final selection should always be based on an analysis of the production process.
Clear or treated water drainage
For residential or commercial systems handling water without significant solids — such as rainwater or lightly contaminated process water — the Lowara DOC series is the compact and reliable solution, offering suitable materials and a reduced footprint.
The value for installers and distributors
Choosing correctly between a submersible pump and a grinder pump means fewer post-installation call-outs, greater reliability from the end user’s perspective and shorter installation times. It also means more efficient stock management, supported by a consistent product range and clear performance curves.
Lowara supports installers and distributors with detailed technical documentation, selection tools and continuity of supply, including genuine spare parts. The goal is to turn every generic enquiry into a technically justified proposal, delivering measurable benefits in terms of efficiency, reliability and profitability.
In civil drainage, the difference between a system that works reliably and one that generates recurring problems is almost always decided during the selection phase. Choosing the right product today is a tangible competitive advantage — both for the project and for the business.
Fabio Zanin
Business Developer, AW Trade, Italia & Iberia