How often to clean what

Milk that dries inside the tip cooks onto the steel and will not brush off later. A wand cleaned within seconds of use stays clean indefinitely; one cleaned tomorrow needs soaking.

You need: A damp cloth kept only for the wand. A pin or the tip key for the holes. Milk-system detergent such as Rinza or Puly Milk for the weekly soak.

What goes wrong: Wiping without purging, so milk stays inside the tip and sours. Letting the wand cool before wiping. Opening the tip holes out with a drill bit or a thick needle, which permanently ruins the steam pattern. Using the same cloth for the wand and the drip tray.

An automatic milk system is a pump, a tube and a frothing head, all holding milk at room temperature between drinks. It is the least forgiving part of a super-automatic and the usual reason one starts to smell.

You need: The maker's milk-system cleaner from Jura, DeLonghi or Philips, or a milk detergent such as Rinza where the manual allows it. A container for the rinse output.

What goes wrong: Relying on the automatic rinse and never taking the head apart. Missing the air-intake hole, which makes the froth collapse and reads as a broken machine. Using coffee detergent on milk protein. Leaving the tube sitting in the milk carton in the fridge.

A film on the prism is a measurement error you cannot see.

You need: Lint-free cloth or lens tissue. Distilled water. The cap it came with.

What goes wrong: Wiping with a paper towel, which scratches the prism. Zeroing against tap water, whose dissolved solids are the thing you are trying to measure. Reading a hot sample, which reads differently from a cooled one.

The injection jet is a narrow hole, and a blocked one changes the brew completely.

You need: Hot water. Washing-up liquid weekly. Nothing abrasive.

What goes wrong: Storing it with the plunger pushed in, which flattens the seal over time. Poking the jet with wire, which widens it and permanently changes the flow rate.

Milk dries onto a thin wire coil in minutes and is very hard to remove later.

You need: Hot water. Washing-up liquid weekly. A cloth.

What goes wrong: Running the motor body under the tap, which is how most of these die. Letting milk dry on the coil and then scraping it off, which bends the wire. Leaving it standing in a wet mug.

Aluminium phins hold oil in the perforations and go rancid quietly.

You need: Soft brush. Washing-up liquid. A dry cloth.

What goes wrong: Putting it away wet and stacked, which is how a phin starts tasting stale. Scouring aluminium with a metal pad, which scratches it and gives oil somewhere to sit. Running it through a dishwasher, which will dull and pit the metal.

Glass and a slow valve are where cold brew grows things.

You need: Bottle brush long enough for the tower. Washing-up liquid. Spare paper filters, or a cloth filter kept wet.

What goes wrong: Letting a cloth filter dry out, which locks the trapped oils in and taints every later brew. Leaving the valve half-open to dry, which lets it stiffen. Cleaning the glass with anything abrasive.

The three-way valve lets you push water backwards through the shower screen and out to the drain, which is the only way to clear the oil and grounds that collect behind it. Neglect it and every shot picks up a stale, ashy edge no matter how good the coffee is.

You need: A blind, or blank, basket for your portafilter and a coffee detergent such as Cafiza or Puly Caff. About 3g of powder - a level scoop, not a heaped one.

What goes wrong: Backflushing a machine with no three-way valve. Overdosing the detergent. Stopping after the detergent stage, so the next four shots taste of soap. Never brushing the screen, so the detergent lifts the oil and it settles straight back onto it.

Coffee leaves a brown film on glass and a duller one on steel. It is not a stain, it is oil, and it goes rancid - a thermal jug that has never been properly cleaned adds a stale note to everything poured into it.

You need: A long-handled brush. Bicarbonate of soda, an oxygenated cleaner such as Cafiza, or a denture tablet. Hot water.

What goes wrong: Leaving the pot on the hot plate to dry out, which bakes the film on hard. Cleaning the jug and never the lid. Dishwashing an insulated jug. Taking a scourer to glass and leaving scratches that hold more oil than before.

A basket that looks clean has oil in every one of its holes and around the rim where it meets the gasket. It changes the flow pattern before it changes the taste, so it shows up as channelling first.

You need: Cafiza or Puly Caff. A jug of hot water. A brush. A towel.

What goes wrong: Soaking the whole portafilter, handle and all. Under-rinsing. Taking a wire brush to a precision basket and enlarging the holes. Skipping the rim, which is exactly where the gasket seals.

A sieve with fines welded into the mesh sorts nothing.

You need: Soft brush. Warm water monthly. A dry towel.

What goes wrong: Pushing a brush hard into the mesh, which deforms the apertures and quietly changes what the sieve does. Stacking them damp. Using a wire brush.

A siphon cloth holds oil and dries out hard. A dried filter brews slower and tastes of the last four brews at once, and one that has been left dry even once never fully recovers.

You need: A small pan for boiling. Water only, no soap. A sealed container for the fridge.

What goes wrong: Washing it with soap. Air-drying the cloth between uses, which is exactly what ruins it. Storing it in water at room temperature, which grows mould in days. Persevering with a filter that has gone grey and slow instead of replacing it.

A group brush lives in coffee oil and heat, and it is the dirtiest tool on the bench.

You need: Espresso machine cleaner. Hot water.

What goes wrong: Never cleaning it at all, which is normal and makes it a source of rancid oil. Leaving it bristles-up so water sits in the head. Replacing it later than every six to twelve months.

The screen and the recess above it hold a film of coffee oil that no amount of shot-pulling shifts. It is the most common reason a well-dialled machine slowly starts tasting muddy.

You need: A screwdriver or hex key for the screen bolt, a soft brush, and Cafiza or Puly Caff for the soak. A group brush for the underside.

What goes wrong: Working on a hot group and burning a hand. Overtightening the bolt and dishing the screen. Soaking and refitting without brushing the recess, so the oil is still there. Losing track of the dispersion block's orientation.

A gooseneck kettle scales faster than anything else on the bench, because it boils every day and never gets rinsed. Scale on the element makes it slower and noisier, and flakes end up in the brew.

You need: Citric acid, about 10g, or white vinegar, about 200ml. Water. A soft cloth.

What goes wrong: Scouring the element and destroying the coating, which then scales faster than before. Rinsing once and brewing a pour-over that tastes of vinegar. Descaling the body and ignoring the gooseneck, so the flow rate stays wrong and you re-dial your pour for nothing.

The plunger is three or four separate discs that trap grounds and oil between them. Rinsing the beaker does nothing about that, and the trapped oil is what makes an old press taste rancid.

You need: Washing-up liquid, or a scoop of oxygenated cleaner for a soak. A bottle brush. A tea towel.

What goes wrong: Rinsing the beaker and never taking the plunger apart. Reassembling wet. Forcing a distorted mesh back into service and blaming the grinder for the sediment. Putting an insulated steel press through a dishwasher.

Cold brew runs for 12 to 20 hours at room temperature with the filter holding wet grounds the whole time. A filter that has been rinsed but never cleaned develops a musty note that carries straight into the concentrate.

You need: Hot water. Washing-up liquid for mesh filters, water only for felt. A soft brush. A sealed container for the fridge if the filter is felt.

What goes wrong: Soap on a felt filter. Letting a felt filter dry out. Cleaning the vessel and forgetting the spigot. Storing everything damp and sealed, which is how the mustiness starts.

A stepped conical grinder holds stale grounds in the chute more than in the burrs.

You need: Stiff dry brush. Dry cloth. Optionally grinder cleaning tablets every few months.

What goes wrong: Washing burrs in water, which rusts them. Putting the hopper back without seating the burr ring, which throws the grind off completely. Using a damp cloth inside the burr chamber.

No pump and no boiler, but the cylinder and piston seals still collect oil and scale.

You need: Espresso machine cleaner such as Cafiza. Food-safe silicone grease for the seals. A soft cloth.

What goes wrong: Greasing the seals with anything not food-safe. Leaving cleaner in the cylinder and pulling the next shot through it. Forcing the levers when the piston is dry, which tears the seals.

A vacuum canister is only as good as the gasket, and coffee oil hardens it.

You need: Warm soapy water. Damp cloth. A spare gasket, since it is a wear part.

What goes wrong: Submerging or dishwashing the lid, which kills the pump. Never checking the gasket and assuming the vacuum still works. Storing beans in it while damp inside.

Scale on the boiler wall and in the group's water path drops brew temperature, blocks the steam tip, and eventually coats the temperature probe so the machine no longer knows how hot it is. On a tank machine this is the maintenance that decides whether it lasts five years or fifteen.

You need: Citric acid powder, about 15g per litre, or a proprietary espresso descaler. A vessel to catch the output. Your machine's manual - the sequence differs per boiler layout.

What goes wrong: Descaling hot, which etches brass. Mixing the solution as strong as a kettle descale. Flushing once and then pulling a shot that tastes of lemons. Ignoring the steam path, so the wand stays blocked and the boiler probe stays coated. Using vinegar in a machine whose maker forbids it - most espresso makers do.

The cartridge in the tank is what keeps scale off the element between descales. An exhausted one stops filtering and starts shedding - carbon fines, and whatever it has been holding onto.

You need: The correct cartridge for your machine - Breville BWF, Jura CLARIS, DeLonghi or Philips AquaClean, Keurig charcoal, or the maker's equivalent. A jug of water for soaking.

What goes wrong: Skipping the soak, then wondering why the pump rattles and runs dry. Forgetting to reset the counter. Treating the filter as a replacement for descaling. Leaving an exhausted cartridge in for months, which is worse than running no filter at all.

Scale insulates the heating element, so the water never reaches brew temperature and the coffee comes out thin and sour. It also shortens the element's life - a scaled machine runs hotter internally to deliver cooler water.

You need: Citric acid powder, about 30g per litre, or a proprietary descaler. Two reservoirs of fresh water for rinsing. No paper filter in the basket.

What goes wrong: Leaving the paper filter in, which collapses and floods. Under-rinsing, so the next three pots taste of citric acid. Using vinegar on a machine whose manual forbids it. Descaling on a fixed calendar while ignoring water hardness, which is what actually drives the rate.

On a saturated-group or plumbed machine the maker's position is to prevent scale rather than dissolve it. Descaling one of these yourself can shift a flake into a gicleur or onto a probe and turn a service into a rebuild.

You need: Hardness test strips or a TDS meter. Whatever softener, resin cartridge or RO and remineralisation setup feeds the machine.

What goes wrong: Running pure RO water and corroding the boiler. Changing cartridges on the calendar while the hardness reading says otherwise. Doing a DIY citric descale on a plumbed machine and dislodging scale into the group. Testing the treated water once at installation and never again.

A super-automatic will not let you reach the boiler, so the built-in program is the only route in. It also counts litres itself and will lock out brewing entirely once it decides you are overdue.

You need: The tablets or liquid the maker specifies - Jura, DeLonghi and Philips each sell their own. A container of at least 1 litre for the output.

What goes wrong: Leaving the water filter fitted, which sacrifices a cartridge. Interrupting the program, which on some Juras forces a restart with a second dose. Skipping the rinse cycles, so the first two coffees taste chemical. Ignoring the machine's prompt for weeks until it refuses to brew at all.

Pod machines have a small thermoblock and a narrow water path, so scale shows up as a weak, slow, spluttering extraction long before anything actually breaks.

You need: The maker's descaling kit, or citric acid at about 10g per litre if the manual allows it. A container for the output.

What goes wrong: Descaling with a capsule loaded. Using undiluted vinegar, which perishes the small internal seals these machines use. Rinsing with one tank instead of two. Treating a blocked pod-piercing needle as scale when it is dried coffee - that needs a paperclip, not descaler.

Scale builds on the copper heating element and drops your brew temperature below the 96°C the machine is built around. A scaled Moccamaster brews cooler and flatter, and the element works harder to get there.

You need: Citric acid powder, about 30g, or a citric-acid based descaler such as Durgol Swiss Espresso. Fresh water for two rinse cycles. No paper filter.

What goes wrong: Leaving the paper filter in the basket, which floods the counter. Rinsing only once, so the next pot tastes sour and metallic. Letting the machine sit switched off with descaler in the reservoir overnight, which attacks the element instead of the scale. Using vinegar and then wondering why the coffee smells of vinegar for a fortnight.

The group gasket hardens and compresses with heat. A dead one leaks around the portafilter, makes the handle sit further and further clockwise, and lets pressure escape that should be going through the puck.

You need: The correct gasket for your group - 8mm or 8.5mm thickness for an E61, model-specific elsewhere. A gasket removal tool or a corkscrew. Food-safe silicone grease, optional.

What goes wrong: Choosing thickness by guess instead of measuring the old one. Scarring the group seat with a screwdriver. Leaving fragments of the old gasket in the seat. Replacing on a schedule while ignoring the handle position, which is the actual indicator.

The rubber gasket is what lets pressure build in the lower chamber. A hardened one leaks steam at the seam, the pot takes forever, and the coffee comes out weak. The perforated filter plate clogs at about the same rate.

You need: A gasket and filter-plate set sized to your pot - 3-cup, 6-cup and 9-cup are all different. Hot water.

What goes wrong: Buying a gasket for the wrong cup size. Dishwashing an aluminium pot. Fitting a new gasket and reusing a clogged filter plate. Overtightening the chambers to stop a leak, which distorts the seat and makes it worse.

The rubber seal is the only thing making an AeroPress a pressure brewer. Once it hardens the plunger slides too easily, air escapes past it, and the brew goes weak and thin with no obvious cause.

You need: A replacement seal for your model - the XL seal is not the standard one. Warm soapy water.

What goes wrong: Storing it compressed, which flattens the seal within months. Diagnosing weak coffee as a grind problem when the seal is passing air. Buying the wrong model's seal. Putting oil or grease on the rubber, which swells it.