I tested mine through 15ft of silicone tubing at about 1.5ft of head, and it filled a gallon consistently at 22-24seconds, so around 150gh, or 2.5gal per minute. That's MORE than I'll need for my cfc
In terms of your chilling speed, that all depends on how much wort you want to cool, and your inlet temp. But yes, I'd you are chilling 5 gallons with recirculated ice water, under 20 minutes is doable. Hell, you could slow the outlet flow rate, and chill it in a single pass