Welcome to Thel-Mar!

Thel-mar is THE manufacturer of the Portable Compound Volumetric Weir.  We are a family owned and operated business for over 40 years.  All of our products are 100% made in Ohio, USA. Thel-mar distributes our weirs internationally.

The Thel-mar Volumetric Weir is the most accurate and affordable portable flow-measuring device in the industry. Our faceplates are laser engraved for longevity and have been proven to be the most accurate solution for highly variable, partially full pipe measurement.