Dead Space in Keggle's

I have recently made an all grain system using 15.5 gallon keggles. I want to use them on a 3 tier gravity system brewing 5 gallon batches. I am in the process of measuring dead space and was shocked when I found the dead space in my boil kettle to be 2 gallons (space from bottom of valve to bottom of the kettle). I was expecting around a gallon. Because the valve is in about the same place on my mash tun I expect to have around 2 gallons loss in my the mash tun as well but I have not measured it yet. My question is "Will this be too much loss due to dead space and how much will I have to adjust recipes to compensate?"

Get yourself some dip tubes from bargainfittings.com ... Awesome place! They connect via compression fittings at the bulkhead inside the keg and dip to the bottom. I have a center adoptive in my mashing (goes through the false bottom) and I lose a cup, if that. The BK will have the same setup soon as I've tried many ways to filter my wort to the fermenter. This seems th best fit (false bottom and center diptube) with my setup as I only use whole hops. I hear that the FB in a boil kettle can clog with pellets. Hope that helps!

You need to attach a dip tube to the inside of your drain outlet.
A dip tube will pick up the liquid below the level of the drain outlet and can be adjusted to remove all but the last pint or two of liquid in your keggle.

Just had an "Awe Duh" moment. Thanks guys. I saw those on bargain fittings when I ordered my valves and it didn't even click that's what they were for.

In my kettle and HLT I use 90* elbow, and the BK has a male hose barb attached to the elbow. In either case it takes the liquid pick-up level down to the bottom of the vessel. A pick-up tube is the same thing, I just made do with what I had laying around in extra SS parts.