Espresso equipment fails in taste before it fails mechanically. Rancid coffee oils build up in the group head and the basket, and they contribute a bitter, stale note to every shot long before anything stops working. Most people diagnose this as bad beans.
There are two separate maintenance jobs, and they are frequently confused. Backflushing removes coffee oils. Descaling removes limescale. Different chemicals, different intervals, different parts of the machine.
Daily
- Purge the group for a second or two before and after each shot.
- Wipe the group gasket with a damp cloth and brush the underside of the shower screen with a group brush after the last shot of the day.
- Purge and wipe the steam wand immediately after every use. Milk that dries inside a wand is difficult to remove and it is the least pleasant part of a neglected machine.
- Rinse the portafilter and basket in hot water. Do not leave a puck sitting in the basket overnight.
The steam wand point is worth emphasising: purge into the drip tray for a second immediately after steaming, before wiping. That clears milk from inside the tip, where a cloth cannot reach.
Weekly: backflushing
Backflushing forces water and detergent backwards through the group head, flushing out oils that accumulate above the shower screen. It requires a machine with a three-way solenoid valve — most pump machines with a proper group have one; many entry-level and pressurised-basket machines do not. Check the manual before attempting it.
- Put a blind basket — the one with no holes — in the portafilter.
- Add roughly 3 g of espresso machine detergent (Cafiza, Puly Caff or equivalent).
- Lock the portafilter in and run the pump for 10 seconds, then stop for 10. Repeat five times.
- Remove, rinse the portafilter and basket thoroughly.
- Repeat the whole cycle with no detergent, five more times, to rinse the group.
- Pull a shot and discard it.
Detergent residue in a group head tastes appalling and it is a common outcome of skipping step 5. Rinse more than you think you need to.
Soaking the portafilter and baskets
Weekly, dissolve a little of the same detergent in hot water and soak the baskets, the shower screen if it removes, and the portafilter basket only. Keep the portafilter handle out of the water if it is plastic or wood, and do not soak brass or chrome for long.
Monthly to quarterly: descaling
Scale forms on the boiler and in the water paths. It reduces heating efficiency, causes temperature instability, and eventually blocks passages.
Do not use vinegar. This matters more in espresso machines than anywhere else. Acetic acid attacks the brass, aluminium and rubber seals used in boilers and group heads, and the smell is extremely difficult to purge from a machine with significant internal volume. Use the manufacturer’s descaler, or a sulphamic or citric acid product made for espresso machines.
- Empty the water tank and fill with descaling solution at the stated dilution.
- Run solution through the group in stages, and through the steam wand and hot water tap, following the machine’s procedure.
- Leave it to dwell for the stated time.
- Flush with at least two full tanks of clean water.
- Discard the first shot afterwards.
How often
| Water | Descale |
|---|---|
| Soft or filtered | Every 6 months |
| Moderate | Every 3 months |
| Hard | Monthly to every 6 weeks |
The better answer is to stop the scale arriving. A filter jug, an inline filter, or bottled water with a low mineral content removes most of the problem — though note that fully deionised water is not ideal either: it tastes flat, some minerals are needed for extraction, and pure water is corrosive to some boiler materials. Aim for low-to-moderate mineral content rather than zero.
The gasket
The group gasket is a rubber ring that seals the portafilter. It hardens and shrinks with heat over time. Symptoms of a worn gasket:
- Water leaking around the portafilter during a shot
- The portafilter handle sitting progressively further round to lock
- Difficulty locking it in at all
Replace every 9 to 12 months with regular use. It is an inexpensive part and a straightforward job — lever the old one out with a screwdriver or a gasket tool, clean the seat, press the new one in. Replacing the shower screen at the same time is sensible.
A working schedule
| Task | Frequency |
|---|---|
| Purge and wipe group, purge steam wand | Every use |
| Brush group, rinse portafilter | Daily |
| Backflush with detergent | Weekly |
| Soak baskets and shower screen | Weekly |
| Descale | 1–6 months by water hardness |
| Replace gasket and shower screen | Annually |
| Clean water tank | Monthly |
If shots have gone bad
Before changing beans or grind, work through this: backflush thoroughly, soak the basket, replace the shower screen and gasket, and descale. A machine with six months of oils in the group produces bitterness that no adjustment to the recipe will fix — and the difference after a proper clean is usually obvious in the first cup.
Common questions
Why should I never use vinegar in an espresso machine?
Acetic acid attacks the brass, aluminium and rubber seals used in boilers and group heads, and the smell is extremely difficult to purge from a machine with significant internal volume. Use the manufacturer’s descaler or a sulphamic or citric acid product made for the purpose.
What is the difference between backflushing and descaling?
Backflushing removes coffee oils from the group head using a detergent and a blind basket — weekly. Descaling removes limescale from the boiler and water paths using an acid — every one to six months by water hardness. They are different chemicals solving different problems.
My machine has no three-way valve. Can I still backflush?
No — without a solenoid valve there is nowhere for the backflush water to go, and forcing it can damage the pump. Instead, soak the portafilter basket and shower screen weekly in the same detergent solution, and keep the group brushed.
Why do my shots taste bitter even with fresh beans?
Before changing the recipe, work through the maintenance: backflush thoroughly, soak the basket, replace the shower screen and gasket, and descale. Six months of rancid oils in a group head produce a bitterness that no adjustment to grind or dose will fix.
How do I know the group gasket needs replacing?
Water leaking around the portafilter during a shot, the handle sitting progressively further round to lock, or difficulty locking it at all. Replace every nine to twelve months with regular use — it is an inexpensive part and a straightforward job.