You don't want to add water now- you'll just water down your beer. I usually make 5.25 gallons in the primary and then have 5 gallons in the secondary. Still, I lose some to trub at times. I just settle for a little less beer that tastes great rather than worrying about the yield. I still might get 48 bottles of a batch, so that's fine with me!
Broken Leg Brewery
Giving beer a leg to stand on since 2006