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Plastic Underdrain Filter

​Trilateral® HDPE
 Plastic Underdrain

The Roberts Filter Group’s Trilateral® plastic underdrain filters incorporate innovative hydraulic design to uniquely guarantee balanced flow backwash distribution. Drawing on more than 125 years of industry expertise, the triangular internal chamber is engineered to optimize air scour capabilities in any conditions, without the need for custom design. And because Roberts can simulate any system’s characteristics at our own manufacturing and testing facility, you can trust your installation will perform even before it’s shipped. 

Plastic Underdrain Filters 
Trilateral HDPE Plastic Underdrain

Plastic Underdrain

Manage Filter Backwash

During a filter backwash cycle, the internal structure must efficiently balance air and water, regardless of changing flow rates or seasonal water temperature fluctuations. If not, conventional filter backwash cycles will be ineffective, maldistribution of water will lead to poor washing, and your system’s effectiveness will be undermined.

Trilateral HDPE Plastic Underdrain
Trilateral HDPE Plastic Underdrain

Affordable Solution

Roberts many years of experience with designing and producing new products, affords Roberts to be a leader in the industry. Although not being the first to introduce Trilateral®, at Roberts, we study, evaluate, and Improve where we see a product lacking the final designs to make the product reliable.


Combined with a reinforced porous plate and long-lasting material, the Trilateral® plastic underdrain filter is the industry’s most reliable and economical solution. 

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