Not getting enough through my tun

So I did a brown ale this weekend and had some problems. I would love for some help cause is cannot figure out where I went wrong. I was making a 5 gal batch and only ended up with about 4 gallons after I sparged. Total water used was 7.2 gallons. Did the grain soak that much up and what can I do to next time this happens.

Let us know what equipment your using.

How much grain?

How much wort left in the bottom of the tun (dead space)?

What equipment are you using.

How much dead space? How much grain?

With my system, for an average grain bill of about 12 lbs I can count on using about 8 gallons to get 6.5 pre boil, ending up with 5 gal in the fermenter.

Th e easy way to figure it out is to know how much your boil off is. Mine is about 1.5 gal. Then shoot for that amount after sparge. I measure what I get after the first run off. For example I can use 4 gal, but after mash I usuallly end up with about 2.5 gal. I then know that I neeed 4 more gallons to get rhe 6.5 that I neeed .Since the dead space is full and the grain cannot absorb any more water, i know I need 4 gallons pf sparge to get my 6.5 target.

Simple.