Wort chiller for 15 gal Megapot

[dbr549]

I need a wort chiller for my 15 gallon Megapot. I plan on doing 5-8 gallon batches. Do I need a 25' or 50' copper chiller. Since 5 gallons is so low in volume, I wonder if 25' would be sufficient. I like to brew dark beers. Any suggestions?

 

[lumpher]

25' would be plenty, but might you go to 10 gallons? If so, go with 50. If only ever 5 gallons, go with 25. Dark or light beers is not a consideration.