Mashing and Sparging - How much water?

[Shoit]

I was just reading some of the brewdays threads and noticed this thread:

viewtopic.php?t=15516&postdays=0&postorder=asc&start=15

How do you know how much water to mash with and then how do you end up with the correct amount of wort?

Kevin

[Matt]

Shoit,

The SOP for mashing is 2.5 - 3 litres of water per kilo of grain.

There is a batch sparge water calculator on the site here

I fly sparge and simply use the same amount of water as my brewlength, so sparge with 23 litres of water. This makes about 32 litres after sparging and boils back down to 23.

Matt

[Danny]

The ratio for mash is anything between 2:1 or 3:1 really .. so for a 4.5kg grain bill you're looking at about 11litres of water or so ... for sparging you simply keep collecting until you reach a gravity of 1005 or you run out of room in your boiler ... so your collection in the boiler is likely to be anything around the 30l mark but after 90min boil you'll be back down to around 23l ..

[anomalous_result]

how do you end up with the correct amount of wort?

You work backwards. You know how much you want your length to be, say 23L. Well you know that you'll lose some to evaporation, during a 90minute boil it might be 15%, so you need (23/85)*100 = 27L to boil... except you'll also lose some to the hops/trub, so that's another litre or more, maybe 3. So you need to start the boil with 30L say.

Then it's just down to which technique, batch or fly sparging you use as to how you go about getting that figure in the boiler. If batch sparging you continue as follows...

To get 30L you'll want two equal batches of 15L from the mash tun, but there are losses in the mash too. There's some deadspace, volume that isn't drained, and the grain soaks up some water as well. Using DaaB's example say the deadpsace is 1L and the grain soaks up 4L (from a 4kg grain bill at 1L per kg) you'll actually need to add 20L to the tun to get your 15L batch. However you don't mash with all that. You mash at your ratio of say 2.5:1 which means with the 4kg bill you mash with 10L. After your 90 minutes or whatever you add another 10L, you let it sit for a bit then run it off.

For the next batch, because the deadspace will be full and the grain will be damp you just need to add the difference between what you've got from the first batch and what you need in the boiler (ideally 15L). Ie if you run off the first batch and find yourself short you can add a bit more for the second batch.

[MartialAnt]

Wow this makes interesting reading. I just buy 30L of water & hope for the best.