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Water makes up more than 90% of the final product. Yet for many brewers, it remains the most difficult variable to master. Even before talking about chemistry or minerals, the first step to success lies in mastering your volumes.
Nothing is more frustrating than ending up with 15 liters in bottles when you were aiming for 20, or getting a beer that is too light because you oversparged your grains. Here’s how to take control of your setup.
1. Understanding the volume chain
To stop brewing “by feel”, you need to break your brew day down into three distinct volume stages:
- Mash volume: This is the water you heat first to mix with your malt. A ratio of 2.5 to 3 liters of water per kilo of grain is generally used.
- Sparge volume: This is the water (often at 78°C) that flows through the grain bed to extract the remaining sugars.
- Pre‑boil volume: This is the total amount of liquid in your kettle before turning on the heat for the hopping stage.
2. The loss chart: Why does your water “disappear”?
Between the mash tun and the bottle, your water undergoes several unavoidable losses that must be anticipated:
| Loss source | Average estimate | Impact on 20L |
|---|---|---|
| Grain absorption | 0.8L to 1L per kg of malt | ~5L (for 5kg of grain) |
| Evaporation (Boil) | 10% to 15% per hour | ~3L to 4L |
| Kettle trub & break material | Sediment at the bottom of the kettle | ~1.5L to 2L |
| ESTIMATED TOTAL | Cumulative losses | ~10L to 12L |
Note: To obtain 20 final liters, you will therefore need to heat between 30L and 32L of water in total.
3. The golden rule for quick calculation
If you don’t use brewing software, here’s a simplified method that works in 90% of cases:
Total Volume = (Desired bottled volume × 1.25) + (Grain weight in kg)
The team’s anti off‑flavour tip
If you use municipal tap water, it contains chlorine. Although necessary for potability, chlorine can react with malt compounds and create phenols (plastic or medicinal flavours).
The solution? Very simple: draw your total water volume the day before your brew day into an open vessel. Chlorine is volatile and will naturally evaporate overnight. Your beer will be all the better for it!