Using a salvaged water heater fan

[duhdrew]

i have access to water heater fans they blow thru a 2 and half inch abs pipe anybody have a clue on the cfm or if its possible

 

[dogstick]

I have heard people using an anemometer, which I have one for wind when I go kiteboarding and can't figure out the precise wind but really don't know how you would convert it to cfm. My best guess would be able to compare it to vortex or some other type of fan that you know the cfm of it. Sry I can't help but let us know if you figure it out or not.

 

[dogstick]

I looked for the answer and the conversion from mph to cfm is way over my head in the math subject.