First solo AG batch

Hey all, so I am about to do my first AG batch. I brewed a 10gal batch on national homebrew day with the help of my neighbor, he pretty much just hung out and made sure I didn't screw up, I couldn't have asked for a better beer, it came out great.

So today I am going to do a 10 gal batch and it is a decoction mash using 26.75 pounds of malt. The only question I have is about how much water am I going to need. Here are the numbers and steps I came up with.

7 (6.8) gallons mash water
26pounds malt
Mash at 140-145f for 30min
Remove 2.25gal grist and boil for 15min
Return grist to mash, stabilize and hold temp for 30min or until conversion complete
Sparge with 9-10gal at 170-180f

So I just need some help with the ammound of water I am going to need. Do my numbers look right? Right now I am going to pick up some propane, thanks for the help in advance!

depends on how much quarts per lbs your going to use

Well my plan is to go for the 1-1 ratio (1 pound grain to 1 quart water)

ok well it looks right according to promash about 7 gal mash and 8 or 9 for sparging