Mash Turn

I am just getting into "All Grain" brewing after doing the Extract for a couple of years.  I brew in 5 gallon batchs.  The problem I have is that the book "How to Brew" stated that the mash turn should be sized to the brew size.  My thought was to use a round ingloo cooler but not sure if I should use the 5gal or 10 gal.  The statement in the book is that there may be an issue with a larger size as to sparging the mash and it compacting to much.  Can anyone help a newbe. 

Thanks  Carl

I'd getty bigger than 5 gallons.  I use a 12 gal tun for 5 and 10, gal batches.

  I also recomend a minimum of a 10 gallon Igloo.  For most brews it has enough volume, although I have a couple recipes that I need my 15 "Cube".  My manifold w/ false bottom fits both. 
  I have only had 1 stuck sparge and that was because of my own error (installed the manifold upside down, duh) and too fine a grain crush.  I ran 2 brews that day with the same grind.  The second brew I installed the manifold correctly and added rice hulls, it worked perfectly even with a powdery grain bed.  Just be patient and draw off the mash SLOWLY!

A mash-tun that is the same as your batch size can make a beer up to about 1.050 gravity.  You can squeeze a couple extra points out by filling it to the brim, or with a really thick mash....but, I've done that a few times and it kinda sucks all the fun out of a brew. 

A mash tun that is twice your batch size allows you to make pretty much anything below 1.100.  It might still be a struggle to make a 1.120 all-grain, barley-wine.  In that case though extract or simple sugar is almost always part of the grain bill anyway. 

I used a 5 gallon round cooler for many years.  It worked fine for all those 1.050-1.055 "standard" beers.  Both of the round coolers make for a very deep grain bed, when full.  This CAN be an issue for causing a stuck sparge.  I never had any actually get STUCK, but I did have a few that drained VERY slow.  I would be concerned that the 10 gallon would be worse if it were full.  I know a lot of people use them successfully though. 

I have a 12 gallon Ice Cube, now.  I simply moved by old 5 gallon round false-bottom over to the cube.  NOTE: I batch sparge.  The small false bottom would not be ideal if I fly-sparged.  I wouldn't get good flow near the cooler walls, especially in the corners.  But, since I batch sparge..its a non-issue.  I like the shorter mash-bed afforded by the greater footprint of the Ice Cube.  Plus, the Ice Cube coolers are a lot cheaper for the volume you get compared to the round coolers.

With the 12 gallon cube I can easily stir the mash without worrying about splashing over the sides.  I can drain without worrying about  stuck sparge.  I can basically make any beer I want, 5 gallons up to 1.110ish, 10 gallons up to 1.070ish, 15 gallons 1.045ish.