I am brewing with a 25l HLT, 30l Mash tun and 52l boiler.

I am boiling 20l to 25l water in the HLT and losing some water during the Mash and Sparge.

By the end of the sparge I am getting about 15l in the boiler. However I am losing lots during the wort boil, with my latest brew I ended up with less than 9 liters.

Any ideas of ways I can stop the loss of so much liquid?



  • What's a HLT? And is this about evaporation during boil or about amount of liquid kept in used malt? Because answers would be totally different.
    – Mołot
    Sep 22, 2015 at 11:18
  • HLT = Hot Liquor Tank Sep 23, 2015 at 12:27
  • Hi Bob. Other users have tagged this question to be closed as "unclear what you're asking". Perhaps you can add some detail about: 1/ what sort of mash liquid:grist ratio you're using, 2/ what sort of heating (electric element? propane burner?), 3/ how long you're boiling, 4/ any other process details you can add.
    – jsled
    Sep 23, 2015 at 12:44

3 Answers 3


Losses of water in the brewing process are common. There are some that are unavoidable and some that are controllable to a point.

1. Absorption by Grain: Your dry grain will absorb water at a rate of 0.96*(weight of grain). The 0.96 is a ratio, so if you use kg of grain, for every 1 kg of grain, you will lose 0.96 kg of water (~960 mL). If you use pounds, 1 lb of grain will lose 0.96 lbs of water (~436 mL).

2. Losses to Evaporation: Boiling water inherently creates steam. Evaporation rates are highly dependent on vessel size, shape, vigor of boil, ambient humidity etc. etc. etc. So it is impossible to predict yours. Generally evaporation rates are between 5-15% per hour. Only through experimentation will you be able to determine this. It may even change between recipes and brew days! You can do things to limit this by reducing the vigor of the boil (simmer at 100 C / 212 F, as opposed to rolling boil). Additionally, you can reduce the exposed surface area (put a lid half-on your pot), keep in mind however, that in doing so you risk retaining volatile compounds like DMS/DMSO that can give a creamed-corn aroma/flavour if not boiled off, generally considered a flaw.

3. Contraction: If you measure your volume while its boiling and immediately after knocking-out (cooling) you will notice a 4% difference. This is simply due to water occupying more space while hot. This is less of a loss and more of an accounting / recipe development affair.

4. Losses due to Trub and Process These are just part of the process, losses in transfer, to hop material, what is adsorbed by proteins etc. We account for 2% here, but your mileage may vary.

What it comes down to, is that there will be losses no matter what you do. Breweries are forever trying to improve their water consumed : beer produced ratio. A 4:1 is considered good! You will see improvements as you learn and refine your system and process. You are on the right track simply by starting to consider how to do it. Keep that in mind while you're brewing and look for ways to improve.


There are two stages you are "loosing" water, and each have different mechanism:

  1. Mash and sparge

  2. Boil

Let's talk them one at a time.

Mash & Sparge loses

There are two reasons for that. First is stuck filtering. If your malt is dripping wet, but nothing comes from the filter, this is the case. See Preventing a Stuck Sparge for details how to deal with it.

Second reason is water that will simply stay in the grain. If you sparge properly, you want to lose it. It should not contain any fermentables in usable amount, but it will contain tanins and other bad tasting, slow to dissolve substances.


Reduce time of the boil if needed. Make boil less vigorous. Add more water to compensate. Whatever. Don't cover your boil kettle - it will prevent purging DMS out of your beer. If you brew with grains that does not have much of DMS precursors, you can try partially covering your kettle.

The key word is measure. Measure OG of wort before boil. Calculate the amount of liquid you need to have desired OG. If it's lower, let it boil down to that amount. If higher, add boiled water. Then, if you need more boil, continue adding water to cover for boil looses. That's all.


I have two very rough guesses.

First, are there any points where you are boiling uncovered where you could change and cover the pot?

Second, your boiler is 52l? Given how large that is I expect you're producing a lot of steam in the boiler due to its increased surface area. Try skipping the boiler, sparge back into your HLT instead of the boiler. Having the volume of the vessel be closer to the volume of your liquid should slow down your water loss. Try this and see if it helps.

One comment, if you're not worried about water efficiency and are only bothered by the loss of volume, then feel free to add more sterile water at the end.

  • 1
    See @Molot's answer when it comes to when you should not cover the boil.
    – BBS
    Sep 22, 2015 at 15:05
  • I agree that a 52l kettle is probably quite wide and would result in a larger surface area and evaporate more. Using a smaller kettle would probably help. I normally boil off less than 3 liters in 60 minutes. Sep 23, 2015 at 12:32

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