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How troubleshooting works

The Troubleshooter asks four questions in the words you would use at the kitchen counter, then picks the published rules that match and orders them by which lever is biggest. Every rule it uses is on this page. Nothing is scored, and nothing is guessed about your cup.

The four questions

What’s wrong with the cup?Bitter or burnt · Sour or sharp · Weak or watery · Harsh, dry, or drying on the tongue · Muddy, with grit or sediment · Flat — nothing going on · Espresso runs too fast and thin · Espresso drips, chokes or stalls

How did you make it?Espresso machine · Moka pot · Pour-over / V60 / Chemex · French press · AeroPress · Drip machine · Cold brew · Pod / capsule machine

How is the coffee ground?Burr grinder at home · Blade grinder at home · Pre-ground, or ground at the shop

What changed recently?Nothing — it just tastes off · New bag of beans · New grinder, or a new grind setting · Different water · New brewer or machine

The idea behind every rule

Brewing pulls flavour out of ground coffee into water. Pull out too little and the cup reads sour, thin or flat; pull out too much and it reads bitter, harsh or drying. Four things set how much comes out: how fine the coffee is ground, how hot the water is, how long they are in contact, and how much coffee there is for the water. Grind size is the biggest of the four, which is why it is usually the first step. Each brewer gives you a different subset of those levers — a drip machine fixes time and temperature, a pod machine fixes almost everything — so the rules are written per brewer.

How the plan is ordered

Step 1 is the biggest lever for that brewer, usually grind size. Step 2 is time or temperature. Step 3 is the machine itself — cleaning, descaling, warm-up. Notes about what changed recently (new beans, new grinder, different water) sit alongside the plan because they can explain the whole thing on their own. Nothing is ranked beyond that published order, and no step is given a likelihood.

The rules

Bitter or burnt — any brewer except pods — Burr grinder at home / Blade grinder at home (step 1)

What it says: Grind one setting coarser.
Why it should help: Bitter usually means too much has been pulled out of the grounds. Coarser grounds give the water less surface to work on, so less comes out.
What it rests on: Bitterness is the classic sign of over-extraction, and grind size is the biggest single lever on how fast water extracts.
Goes deeper: Grind size chart

Bitter or burnt — French press / AeroPress / Cold brew (step 2)

What it says: Shorten the steep.
Why it should help: Every extra minute the grounds sit in water pulls more out of them. Less contact time means less of the bitter end.
What it rests on: In an immersion brew, contact time is the second lever after grind size.
Goes deeper: French press ratio and timing

Bitter or burnt — Pour-over / V60 / Chemex (step 2)

What it says: Use slightly cooler water: let the kettle sit for half a minute after it boils.
Why it should help: Hotter water pulls more out of the grounds, faster. A little cooler takes the edge off without changing anything else.
What it rests on: Water temperature is a lever on extraction; small changes at the top of the range are noticeable in a pour-over.
Goes deeper: Best pour-over brewers

Bitter or burnt — Drip machine (step 2)

What it says: Use a little less coffee, or a coarser grind. A drip machine gives you no other dial.
Why it should help: You cannot change a drip machine’s time or temperature. Grind and dose are the two things left in your hands.
What it rests on: Drip machines fix water temperature and flow; the reader controls grind and dose only.
Goes deeper: Best drip coffee makers

Bitter or burnt — Espresso machine (step 2)

What it says: Stop the shot sooner: a smaller drink from the same dose.
Why it should help: The last part of a shot carries most of the bitterness. Cutting it shorter leaves that in the puck.
What it rests on: Espresso extracts in sequence; the tail of a long shot is where over-extracted flavours concentrate.
Goes deeper: Espresso grind size

Bitter or burnt — Moka pot (step 1)

What it says: Use lower heat, start with hot water in the base, and take it off the stove the moment it starts to gurgle.
Why it should help: The gurgle is steam forcing its way through spent grounds, and that is where the burnt taste comes from. Hot water in the base means the coffee is in contact with heat for less time.
What it rests on: A moka pot over-extracts at the end of the brew; ending it early and heating gently are the two controls a reader has.
Goes deeper: Best moka pots

Bitter or burnt / Harsh, dry, or drying on the tongue — any brewer except pods — Pre-ground, or ground at the shop (step 1)

What it says: Buy a coarser grind (ask for a filter or French press grind), or grind at home with a burr grinder.
Why it should help: Pre-ground coffee is usually ground fine for drip machines. In a slower brewer that fine grind pulls out too much.
What it rests on: Grind size is the lever; without a grinder at home the only way to move it is what you buy.
Goes deeper: How to grind coffee beans

Sour or sharp — any brewer except pods — Burr grinder at home / Blade grinder at home (step 1)

What it says: Grind one setting finer.
Why it should help: Sour usually means too little has been pulled out of the grounds. Finer grounds give the water more surface, so more comes out.
What it rests on: Sourness is the classic sign of under-extraction; grind finer is the first move.
Goes deeper: Grind size chart

Sour or sharp / Weak or watery — Pour-over / V60 / Chemex / French press / AeroPress (step 2)

What it says: Use hotter water: pour within a few seconds of the boil.
Why it should help: Cooler water pulls less out of the grounds. If the kettle has been sitting, the brew starts cold and stays sour.
What it rests on: Water temperature is a lever on extraction; water that has cooled well below the boil under-extracts.
Goes deeper: Coffee-to-water ratio

Sour or sharp — Espresso machine (step 2)

What it says: Let the shot run longer (a bigger drink from the same dose), and give the machine a full warm-up first.
Why it should help: A short shot stops before the sweetness arrives, and a cold machine brews sour whatever you do.
What it rests on: Espresso extracts in sequence, acids first; yield and brew temperature both move a shot away from sour.
Goes deeper: Espresso machine troubleshooting

Sour or sharp / Flat — nothing going on — changed: New bag of beans (a note beside the plan)

What it says: Check the roast date. Many roasters recommend resting beans several days after roasting; a bag from the last few days can taste sharp and gassy until it settles.
Why it should help: Very fresh coffee releases gas that gets in the way of brewing. A few days of rest changes the cup on its own.
What it rests on: Roasters commonly print a roast date and suggest a rest before brewing; a bag inside that window is the first thing to rule out.
Goes deeper: How to store coffee beans

Sour or sharp / Weak or watery — Cold brew (step 1)

What it says: Steep longer, and use more coffee.
Why it should help: Cold water pulls flavour out slowly. If the brew is thin or sharp, it has not had enough time or enough coffee.
What it rests on: Cold brew relies on time and dose in place of heat.
Goes deeper: Best cold brew makers

Weak or watery — Pour-over / V60 / Chemex / French press / AeroPress / Drip machine / Moka pot (step 1)

What it says: Use more coffee: about 1 gram of coffee for every 15 to 16 grams of water is a common starting point.
Why it should help: Weak is most often just too little coffee for the water. Strength comes from the ratio before anything else.
What it rests on: Dose-to-water ratio sets strength; the 1:15–1:17 range is the usual starting band for filter brewing.
Goes deeper: Ratio calculator

Weak or watery — Pour-over / V60 / Chemex / French press / AeroPress / Drip machine — Burr grinder at home / Blade grinder at home (step 2)

What it says: Grind one setting finer.
Why it should help: If the ratio is right and it still tastes thin, the water is not getting enough out of the grounds. Finer helps.
What it rests on: Once dose is set, grind size is the next lever on how much the water extracts.
Goes deeper: Grind size chart

Weak or watery / Flat — nothing going on — Drip machine (step 3)

What it says: Descale the machine.
Why it should help: Scale makes a drip machine run cooler and slower than it should, and the cup goes flat.
What it rests on: Limescale on the heating element lowers brew temperature; descaling is routine maintenance.
Goes deeper: How to clean a coffee maker

Weak or watery — Espresso machine (step 1)

What it says: Use a little more coffee in the basket, or stop the shot sooner.
Why it should help: A thin shot is too much water for the coffee. More coffee, or less water through it, brings the body back.
What it rests on: Espresso strength follows dose and yield.
Goes deeper: Espresso grind size

Weak or watery / Flat — nothing going on — Pod / capsule machine (step 1)

What it says: Choose the smallest cup size, or run a second pod into the same cup.
Why it should help: A pod holds a fixed amount of coffee. Less water through it, or two pods, is the only way to a stronger cup.
What it rests on: Pod machines fix the dose; cup size is the reader’s one control over strength.
Goes deeper: Keurig not working?

Harsh, dry, or drying on the tongue — any brewer except pods — Burr grinder at home / Blade grinder at home (step 1)

What it says: Grind one setting coarser.
Why it should help: That dry, mouth-puckering feel comes with pulling too much out of very fine grounds. Coarser is gentler.
What it rests on: Astringency is associated with over-extraction and fine particles; coarser grind reduces both.
Goes deeper: Grind size chart

Harsh, dry, or drying on the tongue — Pour-over / V60 / Chemex (step 2)

What it says: Pour more gently: a slow, steady stream and less stirring.
Why it should help: Stirring and hard pouring churn up the fine particles and push more out of them.
What it rests on: Agitation raises extraction in a pour-over; a gentler pour is the low-cost control.
Goes deeper: Best pour-over brewers

Harsh, dry, or drying on the tongue — Espresso machine (step 2)

What it says: Stop the shot sooner.
Why it should help: The drying feel builds through the tail of a shot. A shorter drink leaves it behind.
What it rests on: The tail of an espresso shot carries the compounds behind astringency.
Goes deeper: Espresso grind size

Muddy, with grit or sediment — French press (step 1)

What it says: Grind coarser, wait a minute before pressing, and stop the plunger above the grounds instead of pushing to the bottom.
Why it should help: Fine particles slip through the mesh. Coarser grounds and a gentle press leave them in the pot, not the cup.
What it rests on: A French press filters with a mesh; fines pass through it, so the fix is fewer fines and less disturbance.
Goes deeper: Best grinder for French press

Muddy, with grit or sediment — Pour-over / V60 / Chemex / Drip machine / AeroPress / Moka pot (step 1)

What it says: Grind coarser.
Why it should help: Grit in the cup is coffee dust that got through the filter. Coarser grounds make less of it.
What it rests on: Fines are what pass a paper or metal filter; coarser grinding produces fewer.
Goes deeper: Coffee filters explained

Muddy, with grit or sediment / Harsh, dry, or drying on the tongue / Bitter or burnt — Blade grinder at home (a note beside the plan)

What it says: A blade grinder is the likely cause. It chops unevenly, so every batch has dust in it; a burr grinder is the lasting fix.
Why it should help: Blades make a mix of boulders and dust. The dust over-extracts and slips through filters whatever you set.
What it rests on: Blade grinders have no setting and produce a wide spread of particle sizes; burr grinders grind to a chosen size.
Goes deeper: How to grind coffee beans

Muddy, with grit or sediment — Espresso machine (step 1)

What it says: Clean the shower screen and basket, and check the basket for a damaged hole.
Why it should help: Grounds in an espresso cup usually come from a dirty screen or a basket that is letting them through.
What it rests on: An espresso basket retains the grounds; sediment points at the basket or screen, not the grind.
Goes deeper: Espresso machine troubleshooting

Muddy, with grit or sediment — Cold brew (step 1)

What it says: Grind coarser, and pour the finished brew through a paper filter.
Why it should help: A long steep pulls fine particles into the concentrate. Coarser grounds make fewer of them, and paper catches the rest.
What it rests on: Cold brew is strained rather than filtered; fines pass a mesh but not paper.
Goes deeper: Best cold brew makers · Coffee filters explained

Flat — nothing going on — any brewer except pods (step 1)

What it says: Check the roast date on the bag. Beans that are months past roasting taste flat whatever you do; buy fresher.
Why it should help: Coffee loses its aromatics steadily after roasting. No grind or ratio brings them back.
What it rests on: Staling is progressive after the roast; roast date is the first thing to check for a flat cup.
Goes deeper: Best coffee beans · How to store coffee beans

Flat — nothing going on — any brewer except pods — Burr grinder at home / Blade grinder at home (step 2)

What it says: Grind one setting finer.
Why it should help: If the beans are fresh and the cup is still flat, the water is not getting enough out of them.
What it rests on: A flat cup with fresh coffee is more often under- than over-extracted; finer is the next move.
Goes deeper: Grind size chart

Espresso runs too fast and thin — Espresso machine — Burr grinder at home / Blade grinder at home (step 1)

What it says: Grind finer.
Why it should help: Water finds its way through coarse grounds too easily. Finer grounds slow it down and let it pick up more.
What it rests on: Shot time follows grind size more than any other variable.
Goes deeper: Espresso grind size

Espresso runs too fast and thin — Espresso machine (step 2)

What it says: Use a little more coffee, distribute it evenly, and tamp level.
Why it should help: A thin or uneven bed lets water rush through one side. More coffee, spread evenly, gives it resistance.
What it rests on: Dose and puck preparation set the resistance the water meets.
Goes deeper: Portafilter sizes

Espresso runs too fast and thin — Espresso machine — Pre-ground, or ground at the shop (step 1)

What it says: Pre-ground coffee is almost always too coarse for espresso. Ask for an espresso grind, or grind at home.
Why it should help: Espresso needs a much finer grind than anything else, and it goes stale within minutes of grinding.
What it rests on: Espresso grind is finer than standard pre-ground; a burr grinder is the usual answer.
Goes deeper: Grinder pairing tool

Espresso drips, chokes or stalls — Espresso machine — Burr grinder at home / Blade grinder at home (step 1)

What it says: Grind coarser.
Why it should help: Grounds that are too fine pack into a wall the water cannot get through.
What it rests on: Shot time follows grind size more than any other variable.
Goes deeper: Espresso grind size

Espresso drips, chokes or stalls — Espresso machine (step 2)

What it says: Use a little less coffee, and tamp with less force.
Why it should help: Too much coffee or a very hard tamp adds resistance on top of the grind.
What it rests on: Dose and tamp pressure both add resistance; they are the second and third levers after grind.
Goes deeper: Portafilter sizes

Espresso drips, chokes or stalls — Espresso machine (step 3)

What it says: If it is still slow at a coarse grind, backflush and descale.
Why it should help: A blocked screen or scale in the boiler chokes the flow no matter how you grind.
What it rests on: Restricted flow with a coarse grind points at the machine, not the coffee.
Goes deeper: Espresso machine troubleshooting · Espresso machine cleaners

Espresso drips, chokes or stalls — Pour-over / V60 / Chemex (step 1)

What it says: Grind coarser, and stir less.
Why it should help: A pour-over that stalls is clogged with fine particles. Coarser grounds and a still bed drain freely.
What it rests on: Fines migrate to the filter and block it; coarser grind and less agitation are the controls.
Goes deeper: Grind size chart

Espresso runs too fast and thin / Espresso drips, chokes or stalls — any brewer except pods (a note beside the plan)

What it says: Flow problems are an espresso thing. For this brewer, the closest match is grind size: coarser if it drains slowly, finer if it runs through in seconds.
Why it should help: Only an espresso machine pushes water through under pressure; everywhere else, drain time is grind size.
What it rests on: Drain time in a filter brewer tracks grind size.
Goes deeper: Grind size chart

Bitter or burnt / Harsh, dry, or drying on the tongue — Pod / capsule machine (step 1)

What it says: Choose a larger cup size, and descale if it has been a while.
Why it should help: A pod machine gives you cup size and not much else. More water through the same pod makes a milder cup; scale makes any pod machine taste worse.
What it rests on: Pod machines fix dose and temperature; cup size and descaling are the reader’s controls.
Goes deeper: How to descale a Keurig · How to descale a Nespresso

Sour or sharp / Muddy, with grit or sediment — Pod / capsule machine (step 1)

What it says: Run a hot-water cycle first, choose a smaller cup size, and descale if it has been a while.
Why it should help: A cold machine brews sour and a scaled one brews badly; the small cup keeps the coffee concentrated.
What it rests on: Pod machines fix dose; warm-up, cup size and descaling are the reader’s controls.
Goes deeper: Keurig not working? · Nespresso not working?

changed: Different water (a note beside the plan)

What it says: Water is most of the cup. If it changed, brew once with filtered water and change nothing else.
Why it should help: Very hard, very soft or heavily treated water changes the taste on its own, so it needs ruling out first.
What it rests on: Water chemistry affects extraction and flavour; a single control brew isolates it.
Goes deeper: Coffee-to-water ratio

changed: New grinder, or a new grind setting (a note beside the plan)

What it says: A new grinder needs dialling in from scratch: settings do not carry over. Move one notch per brew until it tastes right.
Why it should help: The same number means a different size on every grinder.
What it rests on: Grind settings are not standardised across grinders.
Goes deeper: Grinder pairing tool

changed: New brewer or machine (a note beside the plan)

What it says: A new brewer is its own variable. Run the manual’s first-use cleaning cycle, then dial in from a standard ratio before judging the taste.
Why it should help: New machines carry factory residue and often brew hotter or cooler than the old one.
What it rests on: Manufacturers specify a first-use rinse; brew temperature differs between machines.
Goes deeper: Coffee-to-water ratio

Sour or sharp / Weak or watery / Flat — nothing going on / Espresso drips, chokes or stalls / Muddy, with grit or sediment — Pre-ground, or ground at the shop (a note beside the plan)

What it says: Some of the usual fixes need a grinder. Without one, dose, water and time are your levers; a burr grinder would unlock the rest.
Why it should help: Grind size is the biggest lever there is, and pre-ground coffee has already set it for you.
What it rests on: Grind size is the primary extraction control; it is unavailable without a grinder.
Goes deeper: How to grind coffee beans

Gear the plan may show

Most fixes are a setting, and a setting is never a purchase. A few are an object the reader has said they do not have — a burr grinder when the grinder is a blade, a descaler for a descale step, a scale for a ratio step. Under those plans, and only those, the tool shows the pick the relevant guide already makes. One pick per kind, fixed here in writing, never chosen by price or commission, and never shown inside a step.

A burr grinder — Baratza Encore ESPThe budget pick in our grinder catalogue: conical burrs with a fine-adjust range that covers espresso through French press, so one grinder serves every brewer on this page. The guide →

A descaler — Dezcal Descaler, 900 gThe universal descaler our cleaning guides already recommend, listed for drip and espresso machines alike. The guide →

Backflush tablets — Cafiza Espresso Machine Cleaning Tablets, 100The espresso cleaning tablets our cleaning guide already recommends, for the backflush step. The guide →

A coffee scale — Black Mirror Basic 3.0 coffee scaleFrom our coffee-scale guide: 0.1 g precision and a timer, which is all a ratio step needs. The guide →

A temperature-control kettle — 1 L digital variable temperature gooseneck kettleFrom our gooseneck-kettle guide: one-degree temperature control, which is the point of a water-temperature step. The guide →

Paper filters — #2 Unbleached Cone FiltersFrom our coffee-filters guide: a standard cone paper filter, which catches the fines a mesh lets through. The guide →

A distribution tool — Normcore WDT Tool V2 (9 prong)From our espresso-accessories guide: the tool for breaking up clumps so the puck is even before tamping. The guide →

What the Troubleshooter never does

It never tastes for you, never promises a fix will work, never gives a percentage or a most-likely-cause label, never shows a product beside a problem a setting can solve, and never uses a model that cannot explain itself. If it has no rule for your combination, it says so.

Questions

Has the Troubleshooter tasted my coffee?

No. It works from what you tell it — the taste you describe, the brewer, the grinder and what changed — and from published brewing principles: what grind size, water temperature, contact time and dose each do to a cup. It never sees the cup.

Why one change per brew?

Because two changes at once cannot be told apart. If you grind finer and use hotter water and the cup improves, you do not know which one did it, and the next bag will send you back to the start.

Why is there no most likely cause percentage?

A number would have to rest on a tasting we did not do. Instead the rules are ordered by which lever is biggest — grind size first, then time or temperature, then the machine — and each card shows its reason so you can judge it yourself.

Fix my coffee →