Immersion chiller and keggle

Doing 5 gallon batches with the ability to do 10. If I'm making my own chiller what dimensions seem to work best? Don't have my lid cut yet but was planning on using a 5 gal keg to wrap around giving me about 9 inch diameter. Seems about 21 inches from bottom to the top of the outside of the keg. With the beginning and ending straight sections I was wondering if 20ft is going to be enough if I ever make 10 gal.

If you plan on making ten gallon batches you should go 50 feet. 20 won't be a very efficient chiller for 10 gallons.

Same question but would 20 be enough for only 5 gal batches in a keggle?

Yes it would work for five gallons, but more length will be faster. Also ground water temps are important to how effective the ic will be.

I'm not sure here the op lives but in WA, hose water is pretty cool. This is assuming I can get my propane burner that I want. We shall see.

Just bought a 50 footer from Nybrewsupply through Amazon, cheaper than on EBay. Don't really see myself doing 10 gallon batches but i like that the coils are stacked higher and the overall height, should be nicer for a keggle.