A Sampling of Commercial Flow Meters


Here are a few commercial flow meters that are on the low end of the cost scale (but still not that cheap).


If you find something better, please let me know.



Venturi with Target
www.watermeters.com -- home of the dlj meter



They sell a wide variety of water meters, including hot water meters, and meters that also output a pulse count for loggers.  As low as $45.

(thanks to Chuck for suggesting this)



King Solar

Look for: FL45101, FL6300, FL46302

Look for Series UV, VFCII

In these meters, the flow pushes a target up a tapered flow -- the greater the flow, the higher the target rises. Easy to read the flow at a glance.  Normally no electronic output.  Mount vertically.

Moderate pressure drop.  Some models can handle the full temperature and pressure range encountered in solar thermal projects.

$75 and up -- over $200 for full temperature and pressure capability.


Look for FLMW, FLMH, FLMW201, ...

Look for series HF


In these meters, the flow deflects a turbine or disk which is restrained by a spring.

High operating temperature and pressure capability.  Moderate to high internal pressure drop.   Mount in any orientation.

$65 and up

Paddle Wheel Meters

Look for RFA, RFI, and RFO series

Look for series SF series


In these meters, the flow rotates a paddle wheel which in turn produces an electronic output signal that is proportional to the flow rate.

Some models can handle the full range of solar thermal temperatures and pressures.

$150 and up -- maybe the cheapest flow meters with electronic output?

Clamp on Flow Meter



Drill a hole in the pipe that is to have its flow measured, and clamp this meter on.

$50 -- up to 120F.