Leftover water after mash and sparge

[SpinMaster]

Brand new all grain brewer here. How much water should be left in the mash tun after transferring to the boil kettle? I did my first all grain batch today and the water level was roughly the same as when I mashed in, about 18 litres. I figured that is kind of a waste of water to have that much left behind.

 

[Yooper]

If you're continuous (fly) sparging, that sounds about right. I normally sparge up to my boil volume, and don't do a continuous sparge, so I use just about the right amount of water total without much left in the MLT.

 

[Gnomebrewer]

As Yooper said, that's about right.

However, when I fly/continuous sparge, I stop the sparge water input when there's about enough water left in the mash tun to get the boil kettle to my pre-boil volume, thus the mash tun ends up with no (or little) water in it (if my boil volume is slightly low, I make it up with water).

What was your efficiency? Most new brewers (and probably the majority of more experienced home brewers) prefer batch sparging - it's easier, faster, more consistent, has no issues with astringency, and efficiency is nearly as high as a perfect fly-sparge (a perfect fly sparge isn't easy to get, so often batch sparging is more efficient). I batch sparge about 9 times out of 10.

 

[Francus]

Putting in my .02 on this. Sparging can be done down to a certain specific gravity of the runoff. For example, for a lighter colored beer stop the sparge when the runoff gets to 1.010-1.012. For dark beers you can go down to 1.005-1.008. Going below that can introduce a bitterness from the grain husks into the boil and on to the finished beer. It isn't noticeable so much in dark beers, but light pilsners or cream ales it can be. I usually sparge down to my boil volume or to the runoff gravity if if it hits that before boil volume. If you've dialed in your equipment you'll most likely never get down to the specific gravity but check anyway. What ever wort/water remains in the mash tun goes down the drain (or street, in my case).

A general rule of thumb is .5 gallons of sparge water for every pound of grain. That usually gets you in the ball park of the specific gravities I mentioned above. Use your hydrometer or refractometer to get you the rest of the way. Or just relax and have a homebrew. Or two.