Identifying Flow Problems
Flow issues cause unpredictable and uneven extraction. You might use the same recipe but get wildly different brew times, flavor profiles, and final bed appearance.
Channeling
Water finds paths of least resistance. Some areas over-extract, some under-extract. Flavor is both sour and bitter.
Clogging
Fines block the filter, slowing flow to a crawl. Brew takes 5-7+ minutes. Risk of over-extraction and bitterness.
Fast Flow
Brew drains in under 2 minutes. Not enough contact time. Tastes weak, sour, and underdeveloped.
Channeling: Uneven Water Pathways
Channeling happens when water exploits cracks, gaps, or low-density areas in the coffee bed instead of flowing evenly through all grounds.
How to Spot It
After brewing, look at the spent bed. Signs of channeling:
- • Visible cracks or holes in the coffee bed
- • Uneven surface (some areas higher, some collapsed)
- • Grounds stuck high on the side walls
- • Flavor is simultaneously sour and bitter
Common causes and fixes:
1. Poor distribution before pouring
If dry grounds are piled in the center or clumped, water flows around the edges.
Fix: Level the bed by tapping the brewer or using WDT (Weiss Distribution Technique) to break up clumps.
2. Inadequate bloom agitation
If you do not stir the bloom, dry pockets remain. These create low-resistance pathways during main pour.
Fix: Stir or swirl bloom vigorously to ensure all grounds are saturated evenly.
3. Aggressive or turbulent pouring
High-flow pours or pouring directly in the center can excavate the bed, creating channels and pushing grounds up the walls.
Fix: Pour gently in circular motions. Avoid hitting the same spot repeatedly.
4. Uneven grind particle distribution
Low-quality grinders produce boulders and fines. Fines settle at the bottom, creating a dense layer. Boulders create gaps.
Fix: Upgrade grinder if possible. Or sift out fines and boulders for more uniform particle size.
Clogging: Too Much Resistance
Clogging happens when fines (ultra-fine particles) migrate to the filter and block water flow. Your brew slows to a trickle and takes 5-8+ minutes.
Cause 1: Grind too fine
When grind is very fine, the bed becomes dense and fines clog the paper filter.
Fix: Grind coarser. Aim for 2:30-3:30 total time for pour-over.
Cause 2: Excessive fines from low-quality grinder
Blade grinders and cheap burr grinders produce huge amounts of fines. Even at "medium" settings, these fines clog the filter.
Fix: Upgrade to a better grinder. Or use a coarser setting and sift out fines manually.
Cause 3: Excessive agitation migrating fines
Aggressive swirling or stirring can push fines to the bottom of the bed where they block the filter.
Fix: Reduce agitation intensity. Stir gently or only during bloom.
Cause 4: Very light roasts
Light roasts are denser and more brittle. Grinding them produces more fines, even with good grinders.
Fix: Expect slightly longer brew times (3:30-4:00). Or switch to a brewer less prone to clogging (like Kalita Wave with flat bed).
Fast Flow: Insufficient Contact Time
If your brew drains in under 2 minutes, water is moving through too quickly. Not enough time for proper extraction.
Grind too coarse
Low resistance means water rushes through. This is the most common cause.
Fix: Grind finer until brew time is 2:30-3:30.
Pour rate too fast
If you dump all water in 30 seconds, the bed never builds resistance. Water flows straight through.
Fix: Pour more slowly. Spread pours over 2-3 stages.
Channeling (bypassing)
Water finds a single fast pathway and ignores most of the bed. Total brew time is fast but extraction is uneven.
Fix: Improve distribution and bloom agitation (see channeling section).
Insufficient coffee dose
Very small doses (10-12g) do not create enough bed depth for resistance. Water flows through too quickly.
Fix: Use at least 15-20g of coffee for pour-over.
Target Brew Times
These are general guidelines for pour-over methods like V60, Chemex, or Kalita:
- • 2:30-3:30 = ideal range for balanced extraction
- • Under 2:00 = too fast, likely under-extracted
- • Over 4:30 = too slow, risk of over-extraction