LAZERFLO® Low-Profile Underdrain

Simple, Versatile Stainless-Steel Filter Underdrain System

WesTech’s LAZERFLO® is a low-profile, laser-slotted filter underdrain system that provides an alternative to higher-profile plastic-block and stainless-steel teepee-design underdrains. Its interlocking design features factory-assembled strips that nest together and are sized to fit the length of the filter cell. The strips bolt directly to the cell floor, providing true strength to the installation. A small amount of grout seals the space between the filter cell walls and the ends of the underdrain system.

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This simple, yet versatile design is easier to install than block or monolithic underdrain systems, requires no special installation tools or skills, and eliminates installation delays associated with grout-secured underdrains. Installers can walk on the underdrain right away, and because its floor is flat and free of tripping hazards such as nozzles and other protrusions, walking on it is safer for workers.

LAZERFLO strips nested together get bolted to the cell floor
Factory-assembled strips that nest together and bolt to the filter cell floor

The LAZERFLO underdrain’s structural components are constructed of corrosion-resistant stainless-steel materials. The surface includes a proven, laser-cut slot system that supports fine media retention (0.25 millimeter and above) without the need for support gravel. The open plenum support structure provides even, multidirectional air and water distribution throughout the filter cell, eliminating the potential flow-blockage concerns that attend block and teepee lateral underdrain systems.

Only 6 inches (15 centimeters) high, the LAZERFLO allows for deeper media beds in a given-size filter cell. It is also compatible with WesTech’s MULTIWASH® backwash process, which features simultaneous air and water backwash while overflowing trough weirs to help prevent media loss during the backwash process.

LAZERFLO installed with MULTIWASH backwash system
LAZERFLO installation with MULTIWASH backwash


Laser-cut slot openings on the top surface of the LAZERFLO allow water that has passed down through the filter cell and media to enter a secondary chamber that lies below the surface. Regularly spaced nozzles in this secondary chamber include vertical tailpipes that extend to the filter plenum. The openings in each nozzle allow filtrate in the secondary chamber to pass through the tailpipe into the plenum.

LAZERFLO filtration process diagram
Diagram of LAZERFLO filtering process

The LAZERFLO supports both water and air-and-water backwash processes during backwash using the same nozzle and tailpipe system that carries water to the plenum. During the backwash process, water enters the filter cell through a flume in the cell’s floor or side. For backwash processes that include air, an air header, typically within the flume, provides primary air distribution within the filter cell. Air metering orifices are arranged vertically along the sides of the tailpipes. The tailpipes meter air and water, which pass up to the secondary chamber through the tailpipe. The air and water then pass through the secondary chamber and flow up through the LAZERFLO underdrain’s slotted surface and up through the media bed into a backwash water collection system. The LAZERFLO underdrain supports multiple flume and air header configurations.

LAZERFLO backwash process diagram
Diagram of the LAZERFLO backwash process

Benefits and Features

  • Easier to construct and install: interlocking factory-assembled sections that anchor to the floor
  • More effective: an open-plenum design that allows water and air to move in all directions below the floor
  • Better for retrofits: a lower profile that provides greater media depth for retrofits
  • Safer for employees: a completed floor that is flat and free of obstructions
  • Lower profile: 6-inch (15-cm) profile (lower than those of block and monolithic underdrains)
  • Interlocking construction: simpler installation, shorter overall project schedule
  • Laser-cut top deck: fine media support (0.25 mm and above) without the need for support gravel
  • Corrosion resistant: stainless-steel structural components
  • MULTIWASH compatibility: highly effective backwash cleaning system that prevents continual media loss
  • Efficient design: even distribution, minimized feed locations
  • Industrial and municipal gravity filter plants
  • Existing gravity filter retrofits
  • Steel filters, including package plants

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