Concept of Foundation water in a mash tun

I am preparing to brew my first all-grain 5 gallon batch, and I am going to be using a converted Rubbermaid 10 gal cooler as my mash/lauter tun. Just a clarifying question about the use of foundation water.

So basically, am I first draining the tun of the water, letting the grain bed settle? When do I add the foundation water? From my understanding, I am adding the 170 degree water just above the grain bed, holding it for a moment, and then sparging on top of the now floating grain bed. Is this correct?

Thanks!

I'm not sure I understand your question. "Foundation water" is just a fancy term for the water occupying the "dead space." In other words, it's the water that remains in the tun and doesn't drain when you open the valve. You need to account for it in your water volumes, but otherwise, you don't do any special procedure with it. You add your strike water to the tun, add your grain to the strike water, and mix it up. I think you're overthinking it.

I'd answer except that the term "foundation water" has no meaning to me. Does it have something to do with fly sparging? If you're new to all-grain, you may want to consider batch sparging, a simpler process.

If you are looking into batch sparging then visit http://www.dennybrew.com This site will instruct you not only in how to do it properly but also how to construct your tun.

I've only heard the term "Foundation water" when it's applied to a direct fire system that fills from the bottom up. Helps to keep the draff from clogging a false bottom.