JasonLion said:You can get a flow meter for under $100. See for example this site. You need to have a couple of feet (pipe diameter * 14) of horizontal (or vertical with a different model) pipe with no other fittings to install the meter.
Pools should come with flow meters!
Jason, I was actually considering posting the other night to see if there would be any interest in a group buy that we could share. Get enough interested, and it would be pretty cheap to know your flow. I had thought of plumbing something so it could attatch to my return so I'd not have to mess with my other plumbing.