Slow day today, decided to see how well ^that rotameter's^ readings correlate to actual flow rates. Got the big scale out and tared a bucket, put a few gallons of water in the kettle and primed the March pump, set the stop watch for 60 seconds, and opened the valve to a one quart per minute reading.
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After 60 seconds I was amazed at how accurate the meter is at the bottom end as I had collected 2.05 pounds of water (one quart at room temp should be ~2.08). Repeated a couple of times and it was very consistent. Moved to 1/2 gallon per minute and that was equally accurate with the first trial ending with 4.12 gallons (vs ~4.17) and another at 4.13. Repeated for 1 and 2 gallons just for grins and it still read very close.
I was also pleased to see the meter doesn't really restrict the max flow much if at all. Although the indicated max flow is ~2.75 gpm I think it actually flows higher with the indicator slammed against the top of the meter body.
In any case I'm pleased with this thing so far. I've always wondered how fast I was actually recirculating the mash and especially when running out to the kettle as I have found slower runout = higher SG, and now I'll have a much better understanding of both.
Cheers!