Granular Media Stainless Steel Filter Underdrain

Have you seen Orthos’ MAXIMUS™ granular media filter underdrain? Its design solves a number of performance and installation issues and provides excellent distribution, robust stainless steel filter construction, and quick commissioning.



Retrofits of concrete-tankage, granular media filters are perfect applications for MAXIMUS, though because of its relatively-quick installation, new, “greenfield” applications are certainly deserving of consideration. 

After filter leveling, the perimeter frame of MAXIMUS is secured using anchor bolts using HILTI epoxy.  A gasket is placed between the perimeter frame, floor, flume support angle, and flume end plug, as necessary, to seal the bottom perimeter of MAXIMUS.  Nozzle plates are secured to the filter floor using square anchor tubes with epoxied anchors.  Span plates with gaskets are bolted through the nozzle plates and into nuts that are factory-welded to the underside of the nozzle plate.  Nozzle plates and span plates extend over the perimeter frame and are connected with bolts and gaskets to further seal the top of MAXIMUS. The thick, 10-gauge stainless steel perimeter frame, nozzle plates with its robust stiffeners, and anchors will withstand a minimum of 1600 lbs/ft2 uplift force.

Competition’s Triangular-shaped Metal Underdrain Laterals Present Three Concerns:

1. Spacing on 12” centers that creates large dead zones between lateral lengths

Lateral Maldistribution
Lateral Spacing

2. The inherent problem of maldistribution down each lateral in a header-lateral configuration

AWI maldistribution

Different holes sizes produce different results at different flow rates

3. The questionable structural integrity of 20 gauge (0.0375 inch) sheet metal

20 Gauge Metal Underdrain
Sheet Metal Failure

MAXIMUS solves all of these problems by effectively creating a 10 gauge (0.1406 inch—4x as thick) plate underdrain with free-flow orifices that in turn create an open plenum, and with nozzles on 6-inch centers each way, excellent flow distribution is assured.

If you must have a low-profile, quick-installing filter underdrain, MAXIMUS will deliver excellent distribution and long-term resiliency. 

Be sure to visit the MAXIMUS™ Free-Flow Filter page!


Stainless Steel Filter Underdrain

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Remember Orthos’ HUGE life cycle cost benefits– At the end of the filter’s life cycle (~25 years), in contrast to a complete plastic block or folded sheet metal underdrain overhaul, nozzles are simply replaced
potentially saving $Millions.

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