Updated October 2026 · bypass water by bean density
Bypass water is hot water added to the cup after the shot. It has bypassed the coffee bed, so it adds volume without over-extraction bitterness. In the Coffee Recipe Series it rises with bean density, from none for the darkest roasts to 30 ml for the lightest, across all 121 espresso recipes.
The lighter the roast, the more hot water and the less milk. No bypass water for the darkest roasts, 15 ml at 0.390 g/ml and 30 ml for the lightest. Measure your beans and your recipe gives you the amount.
Why bypass water?
Light roasts need a low dose and a high ratio. Add a lot of milk, as most people do with flat whites, lattes and cappuccinos, and the delicate notes, fruit, acidity and aromas are easily overwhelmed. Replacing some of the milk with hot water brings out the full range of flavours.
Very dark roasts can be ashy and burnt-tasting. A large volume of milk makes a more palatable drink, so no bypass water is needed.
Bypass is commonly used for Americanos and long blacks. With the trend towards lighter roasts, it should start to be included in milk drinks too. Your coffee is likely roasted somewhere between the extremes, and the right amount of bypass water falls somewhere on the scale.
Across the series
As density rises across the series, bypass water climbs steadily from 0 to 30 ml while the steamed milk falls from 210 ml to 55 ml, and the cup gets smaller.
bypass with 210 ml milk in a 240 ml cup, 0.330 g/ml (Recipe 1)
bypass with 133 ml milk in a 220 ml cup, 0.390 g/ml (Recipe 61)
bypass with 55 ml milk in a 150 ml cup, 0.450 g/ml (Recipe 121)
Your recipe gives the exact bypass water, milk and cup size for your density, so the whole drink is balanced for that roast.
Find your bypassHow to add it
Before adding anything, stir the espresso and crema, dip a teaspoon in and taste. If it's sour or bitter, change recipe first using Extract More or Extract Less.
Add the bypass water from your recipe (optional). It reduces the blanket of milk and increases the coffee's apparent strength while keeping the volume up.
Top up with the steamed milk from your recipe. Adding 5–10 ml of cream to the milk before steaming can help the body and taste, and 15% coconut milk is another great option.
Keep reading
Find your starting recipe, then dig deeper into what drives extraction.
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