How much sparge water do I need?
Whatever gets you to your pre-boil volume after the first runnings. Your equipment profile knows how much wort you need in the kettle, how much the grain keeps, and how much the tun hides — so sparge water is simply total water minus what went in at mash-in. For 11 lb on the default US profile that's 4.4 gal of sparge after a 4.4 gal strike; for 5 kg on the metric default, 17.3 L after 16 L. The full ledger — every volume from strike to keg — lives on the Total Water page; this page is about the two questions it doesn't answer: how hot, and how to split.
What temperature should batch sparge water be?
Every guide says "168–170°F", and every guide is quietly answering a different question. 168°F is the temperature you want the grain bed to reach — where the enzymes stop and the sugars run thin. But once you've drained the first runnings, the bed is a pile of grain at 150°F holding only the water it absorbed. Pour 168°F water onto that and the mix lands in the low 160s. To actually reach 168 the water has to be hotter, and it's the same heat balance as strike water, run forwards:
Twater = Ttarget + (0.2 × grain + retained water) × (Ttarget − Tbed) ÷ sparge volume
qt/lb/°F form; the calculator does it in whatever units you brew in. Retained water ≈ your grain absorption × grain weight.
Ten pounds of grain drained at 150°F, holding 5 qt, sparged with 17.6 qt to reach 168°F: the water needs to be 175°F. The metric default — 5 kg at 66°C, 17.3 L of sparge — wants 80°C. Neither is 170. This is why so many batch spargers report "I sparge at 168 and my bed never gets there": it can't.
| Bed at | Sparge water per lb of grain (qt) · per kg (L) | |||||
|---|---|---|---|---|---|---|
| 1.00 · 2.1 | 1.25 · 2.6 | 1.50 · 3.1 | 1.75 · 3.7 | 2.00 · 4.2 | 2.50 · 5.2 | |
| 146°F · 63°C | 183°F · 84°C | 180°F · 82°C | 178°F · 81°C | 177°F · 80°C | 176°F · 80°C | 174°F · 79°C |
| 148°F · 64°C | 182°F · 83°C | 179°F · 82°C | 177°F · 81°C | 176°F · 80°C | 175°F · 79°C | 174°F · 79°C |
| 150°F · 66°C | 181°F · 83°C | 178°F · 81°C | 176°F · 80°C | 175°F · 80°C | 174°F · 79°C | 173°F · 78°C |
| 152°F · 67°C | 179°F · 82°C | 177°F · 81°C | 175°F · 80°C | 174°F · 79°C | 174°F · 79°C | 172°F · 78°C |
| 154°F · 68°C | 178°F · 81°C | 176°F · 80°C | 175°F · 79°C | 174°F · 79°C | 173°F · 78°C | 172°F · 78°C |
| 156°F · 69°C | 176°F · 80°C | 175°F · 79°C | 174°F · 79°C | 173°F · 78°C | 172°F · 78°C | 171°F · 77°C |
Bed retaining 0.5 qt/lb (1.0 L/kg) of absorbed water; target 168°F / 76°C; heat balance from this page's engine. "—" would need water above boiling: raise the bed some other way or accept a cooler sparge.
The 170°F warning is about the bed: tannins come out of husks when the grain sits above ~170°F and the pH has drifted above ~6 as the sugars wash out — which is a fly-sparging failure mode, late in a long runoff. In a batch sparge the water is in and out in ten minutes and the pH barely moves, so 175–180°F water landing the bed at 168 is exactly right. Pouring boiling water on the bed and letting it sit for half an hour would be a different story; nobody does that.
Batch sparging with equal runnings
For a given number of sparges, you extract the most sugar when every runoff is the same size — the first runnings and each sparge. Denny Conn's method: choose your strike volume so that the first runnings equal what you'll sparge with. On the default US profile with 11 lb, that means striking with 5.2 gal (a thinner 1.79 qt/lb mash), draining 3.6 gal, and sparging with another 3.6 gal — versus the profile's 1.5 qt/lb strike and a 4.4 gal sparge. Total water is identical; only the split moves. The gain is a percent or two of efficiency; the cost is a thinner mash that holds temperature a little less well. Two sparges split it three ways and squeeze out a touch more, at the price of a second round of stirring and draining.
Drain the first runnings completely (vorlauf a couple of quarts until clear). Add the sparge water at the temperature above, stir hard to break up the bed and dissolve the sugar left in it, let it settle five minutes, vorlauf again, drain completely. Repeat if you're doing two. Measure what you collected against the plan; the pre-boil gravity and volume together tell you your efficiency before the boil even starts.
Fly sparging: temperature, rate and time
Fly (continuous) sparging is a different animal: the water trickles in as the wort trickles out, the bed never drains, and its temperature follows the water closely — so here 168–170°F water is the right answer, and the volume is the same sparge volume the ledger gives. What matters is rate: about a quart a minute for a homebrew batch (roughly a liter a minute), keeping an inch of water above the grain, which makes a 4.4 gal sparge a 18-minute job. Faster channels; slower lets the bed cool and the pH rise. Stop when the runoff gravity drops to about 1.010 or the pre-boil volume is reached, whichever comes first — that last quart of 1.006 wort is where the tannins live.