See if this looks right before I start

Before the flames begin, let me say that I'm wanting to brew 1/2 batches for a reason. I know that it takes no more time to brew a full batch, but I'm wanting to experiment with some recipes and get the process down before I make a whole batch. That being said, here's what I'm going to do. Feel free to offer any advice or point out flaws in my thinking.

This recipe is for a German Pilsner beer using Altbier yeast (something like Wyeast 1007) so I can ferment it around room temp.

- mash 5 pounds of German Pilsner malt with 1.75 gallons of water at 150 degrees for 60 minutes
- sparge with 1.5 gallons of water at 170 degrees (I know I should use more, but I don't want to have to boil off several gallons so it'll go into my 3 gallon carboy)
- boil 3.25 gallons from mash and sparge for 60 minutes

Hops
- .5 ounce Hallertau for 60 minutes
- .5 ounce Hallertau for 10 minutes
- .5 ounce Saaz 0 minutes
- I may dry hop with another .25 to .5 ounce of something...I don't know

Promash estimates the OG to be 1.057 with a Plato of 14.04 with an ABV of 4.6%.

I like the idea but I would seriously sparge more and just boil off the rest. my $0.02

How much would you sparge? 3 gallons?

Reduce your mash to 1 1/4 gallon then sparge with 2 1/2 gallons. You will end up with about 3 to 3 1/4 gallons in your brew pot. A 60 minute boil will reduce the volume even more. You might even need to add a bit of water.
Also, remember that you are doing a smaller boil so there is a chance that the wort may darken a bit. This may not be desirable for a pilsner.

EDIT: Remember that approximately .1 gallon of water is absorbed per pound of grain during the mash so you will be losing about 1/2 gallon of water.

Thanks for the input. I'm hoping to start the brew in about a week and a half. I'll let everyone know how it turns out.

I dont know about your system, But... Mine will boil out 2+ gal of H2O in a 60 minute boil. to test your system just add 3 (ar however many) gal of water to your brewpot and just boil away for 30 min cool and re check your volume mulitply by 2 and there you go. this measurment youll need to know for all your recipe formulations in the future. to be 100% boil the whole 60 min then recheck your volume
Good luck
JJ