I recently installed a water flow meter so I could monitor my GPM flow rates. I have a variable speed pump and I was curious as to how low I could run the pump and still get an adequate turn rate. After searching for flow meters I found all different types. Many were hundreds of dollars and meant for commercial applications. I ended up finding a good compromise with an acrylic clamp on style flow meter. The manufacturer is Blue-White and it cost around $100 shipped.
Here are some pix of the installation:
The instructions said for 2" pipe to mount the flow meter 20" from any bends in the pipe before the flow meter, 8" away from any bends after the flow meter. It worked out that I had a section of return pipe that worked out great.
It needed a 5/8" hole in the pvc to insert the meter into the water flow.
You use simple clamps to secure the flow meter to the pipe.
I then tested running my pump at various speeds until I had it running as slow as possible and still giving me the turn rate I wanted. Let me know if anyone wants any more info about it...