Charles M. Allen High Reynolds Number Facility

Achieving a high Reynolds number and a low level of uncertainty are the hallmarks of our Allen test facility.

Water to the Allen facility is supplied from a 200,000 gallon sump that is typically heated to 105°F, but can reach temperatures up to 120°F when needed. Since kinematic viscosity is a strong function of water temperature, we can achieve a high Reynolds number simply by reducing the water’s viscosity by heating the water.

Depending on meter style and pipe size, the facility’s maximum flow is about 20,000 GPM, with a minimum flow of 0.05 GPM. The accredited uncertainty of the Allen facility is less than 0.10% for flows from 1 to 20,000 GPM.

The Allen facility is ISO/IEC 10725 accredited.

Leslie Hooper Low Reynolds Number Facility

Our original flow meter calibration facility, the Hooper facility, was constructed over 100 years ago and still operates today. Flow is supplied from a 150-acre reservoir through a 40-inch penstock, which means that flow can be provided without the use of pumps—for clients with sensitive electronic meters, this is very beneficial.

Water temperature varies seasonally from 32° to 75°F. Because of the low noise gravity feed available in the Hooper facility, we can ensure low differential pressure measurements for low Reynolds number testing.

The maximum flow of the Hooper facility is approximately 35,000 GPM, depending on meter style and pipe size, with a minimum flow of 0.05 GPM. The Facility uncertainty is 0.25% using weigh tanks and 0.50% for flows above 8000 gpm using a secondary standard.


"I've always been happy with the Alden team. Their technical skills, quality of work, and willingness to adapt is what makes them industry leaders."

Nat Sekhar

Environmental Services Professional