I use one and it works great. Once you start agitating at a fairly high speed the wort it will begin to whirlpool, then just use an up and down motion going from the top of the wort to the bottom and this will draw the air into the wort.
I eliminated the worry by sweating a couple extensions onto my wort chiller so the hose connection were outside of the kettle. It also helps keep the hoses away from the flame while the chiller is in the kettle.
I'll have to try your method the next time I brew. I did the snowbank and stir method for my last batch and it took an hour and forty-five minutes to bring the temp down to 70°.
If you have any snow outside you can put the kettle in a snowbank, pack snow around it as needed and stir the wort occasionally to help it cool. Its definitely allot slower than an IC, but it works. I made a batch last week and used the above method and it took about an hour and forty-five...
I have a 52 Qt Coleman Extreme with a stainless steel braid and I am consistently hitting at or above 75% efficiency using grain that I crush at my LHBS.
Have you checked you thermometer to make sure it was accurate?
If you don't see yourself brewing more than 5 gallon batches the 9 gallon pot will be more than sufficient. If you think you may eventually brew larger batches then consider a keggle or the largest pot that is within your budget.
A 36 qt or larger pot would be the best but you can also get by with a slightly smaller one. I use a 32 qt. pot and have boiled as much as 7.75 gallons without boiling over using the technique EdWort demonstrates in his video.
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