Water volume calculation

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ben_sa

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Hi Folks,

I'm brewing my biggest ever beer today, q west coast ipa with a grain bill of 8kg for a final volume of 23-24Litres and I am struggling with my water volumes required...


I normally use the calculation of
2.5L/kg mash in
1.25L/kg mash out
2.5L/kg sparge.

So a normal 6kg batch is about 15/7.5/15

Today I'm brewing an ipa, and using those calculations for 8kgs
20L in
10 out
20 sparge

That sounds like a lot of water???

Am I missing something? I obviously need to up my mash in volume due to extra losses... but 50l for a final volume of 24 seems a lot...

Cheers
Ben
 

Meddo

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How far down the rabbit hole do you want to go? :p

Without knowing the specs of your rig a rough number to look at would be the liqour loss due to retention in the grain. This is typically going to be about 1 l/kg of your total water (after sparging) so you would need to bump your total water up by that amount ( 2 litres total). If you're brewing a hop bomb then you will need to add a bit more to allow for increased kettle/trub loss, say half a litre. So instead of your typical 37.5 l total call it 40 l.

Regarding the distribution of that 40 l, if the mash out volume is for a temperature infusion then you'll need to keep the ratio of strike to infusion (mash out) water roughly the same as you do currently (not exactly but more information would be needed to improve on that as a guide). Note that the temperature loss at mash in will also be a little bit different if you vary your water/grist ratio. For simplicity I'd be inclined to reduce your ratios proportionately to hit the 40 l total, i.e. 16 / 8 / 16 litres (2.29 / 1.14 / 2.29 l/kg). Depending on whether you pre-heat your tun you might need your strike water ~1-2 degrees higher for mash-in, and something similar for your mash-out (reason: the grain is a larger overall component of the total heated mass, so it needs more heat energy to raise to mash temperature and more heat energy to raise to mash-out temperature, but the water volumes are smaller proportionately so need to be hotter).

Note - I'm a 1V RIMS recirc brewer and have never driven a 3V rig - I do have a reasonable handle on the maths but if anyone with more practical experience on such a system wants to overrule me please feel free.
 
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philrob

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I use a 3V system, and simply never bother to calculate water volumes.
On my system, I heat my HLT to 5ºC over my desired mash temperature in summer, 6 to 7ºC over it in winter.
I use a digital thermometer to monitor the mash temperature as I mash in and just slowly add water till I hit my mash temperature spot on.
Post mash I top up the mash tun with 90ºC or so water for my batch sparge mash out, do my run off, and then top up the mash tun again for the sparge.
Hey presto, just like magic, I end up with 34 to 35 litres preboil every time I brew.

I don't know why people fret so much over water volumes. Just brew and keep notes so you know what your system delivers, and it becomes repeatable each time.
Using 1 or 2 or so litres extra or less doesn't affect the quality of your beer.
 

Meddo

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Not sure it's about fretting, but there's two valid ways to approach it. If you're limited in your frequency of brewing, have made changes to your rig, or regularly vary your batch size or target OG you may not get the consistency / muscle memory so it can be handy to do the maths to know in advance what you need and what you'll get. Or you might just enjoy knowing how it works, not just that it does.

If @ben_sa went down the path of 50 l total with that grain bill on his rig he'll wind up with roughly the same beer he always brews in terms of OG unless he increases his boil length substantially to boil off the excess water.
 
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ben_sa

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I actually sat down and thought about it before I brewed, and realised whether you brew 5l or 50l your boil off evap rates will be the same...

Bear in mind I do not ever measure pre boil volumes because I am lazy, something I intend to change asap (after 14 years of brewing haha)

I wound up with 20l mash in, yielded about 13l, 8l mash out of boiling, and a sparge around 13l so just around 41l total.

Would up with 2l trub in the kettle, and it's just chilled so I'll be interested to see if I get my 1.057 I was chasing.

I have learnt that one calculation, is not going to transfer over to a completely different batch, 2.5/1.25/2.5 doesnt mean much unless the grain bill is same weight.

Time to buy a refrac and a measuring stick for the kettle...

Cheers for the help guys, appreciate it. I was really scratching my head earlier but hopefully all has worked out well
 

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