• Duke Energy

  • USDA

  • USGS

  • U.S. Army Corps of Engineers

  • Lockhead Martin

  • Central Park Conservancy, NY 

  • KCI Technologies, Inc.

  • Baltimore County Government

  • ELSCOLAB N.V. Belgium Co.

  • City of Tacoma Public Works, WA

  • Riverside, CA Flood Control


  • Boston University

  • Texas A&M

  • University of Cincinnati

  • University of Maryland

  • University of Massachusetts

  • University of Connecticut

  • Ohio State University 

  • Santa Clare University




Thel-Mar, LLC

Portable Volumetric Weirs

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Purchase directly from us, or feel free to use one of our valued distributors. 


thel-mar brochure

The Thel-mar Volumetric Weir is the most practical and economical calibrated measuring devise used to determine infiltration in newly installed sewer lines, as well as substantial flows in existing pipes.  Our weirs offer the advantage of a 90 degree v-notch for measuring small infiltration flow where accuracy is of prime importance.  The rectangular portion of our compound weir measures larger volume flow rates.

Who uses our weirs?  Municipalities, the USDA, the USGS, the cranberry fields of Massachusetts, Universities, and Commercial and Residential developers.

Our weirs can be manufactured with an optional bubbler tube. They are produced with a 1/8" O.D. stainless steel tube attached to the right side of the adjustable ring to accommodate data logging equipment for continuous remote monitoring.

Our Volumetric Weirs come in 6", 8", 10", 12", 14", 15", and 16" sizes, both as a standard weir or with the bubbler tube. We also carry adapters that house our 15" weir in pipes of 18", 21", 24", 27", 30", 36", 42", and 48" sizes.

The Thel-mar Volumetric Weir offers rugged construction and non-corroding materials that make our weir extremely reliable.  Lehigh University testing showed the Thel-mar Weir measurements to have a +/- 5% accuracy, with a 2% accuracy at moderate and high flow rates.