Why does my moka pot coffee taste bitter?

Most often the heat is too high, which over-extracts the last of the brew in the upper chamber. Lower the flame and remove the pot when the flow turns pale and begins to sputter, before changing the grind.

How fine should I grind for a moka pot?

Finer than filter, coarser than espresso. CupTune's authored planning range is roughly 300 to 500 microns, and it should never be tamped into the basket.

Should I use preheated water in a moka pot?

It is a common technique, intended to reduce how long the grounds sit in the heating chamber. It also means handling a hot base, so follow your brewer's instructions and use a cloth.

Why is my moka pot sputtering violently?

Usually far too much heat for the size of pot, or a grind fine enough to block the basket. If it happens at a sensible heat, check the gasket and filter plate for old grounds.

Symptom by symptom

Moka pot troubleshooting

The moka pot is the most misunderstood brewer in most kitchens, and most of its faults come from heat rather than from coffee.

Water and the safety valve below, the coffee funnel in the middle, the collection chamber above. The valve is the reason the water line is not a preference.

Read the safety part first

A moka pot is a pressure vessel on a hob. Bialetti's own Moka Express instructions say to fill water below the safety valve, fill the funnel loosely without tamping, use low to medium heat and remove the brewer when the top chamber is full. Those are the manufacturer's instructions for their brewer, they override everything else on this page, and you should follow the instructions for the pot you actually own.

Do not open, shake or force a pressurised pot, do not block the valve, and do not leave it on the heat after it finishes.

Bitter, burnt, harsh

Usually heat, not grind. Too high a flame drives the water through fast and then keeps cooking the coffee in the upper chamber. Drop to a lower heat, and take the pot off as soon as the flow turns pale and starts to sputter — that is the point where you are extracting the last, least pleasant fraction. Some people run the base under cold water to stop it hard; that is a technique choice, not a requirement.

If low heat does not fix it, then go coarser. Moka wants a grind finer than filter and coarser than espresso — CupTune's grind chart puts it around 300–500 microns as an authored planning range.

Weak and watery

Usually an underfilled funnel. The basket should be filled level and loose — not tamped, but not half empty either. The other common cause is stopping too early because the first flow looked thin; the concentration builds through the pour.

Sputtering, spitting, erupting early

Heat again, or a grind so fine it has blocked the basket. Violent sputtering from the start usually means the flame is far too high for the size of the pot. If it happens with sensible heat, check the gasket and the filter plate for old grounds.

Nothing comes up, or it stalls

Stop and take it off the heat. A stall usually means the grind is too fine or the coffee was tamped, and the bed has blocked. Let it cool completely before opening. This is the one symptom where the answer is never "turn the heat up".

Metallic or stale taste

Old coffee oils in the funnel, the filter plate or the gasket. Rinse thoroughly after every brew, and replace the rubber gasket when it hardens or stops sealing — it is a consumable part.

What this page cannot do

It cannot assess your specific pot, your hob or the condition of your safety valve. CupTune does not evaluate pressure, burn or equipment safety, and a fault you cannot explain is a reason to stop using the brewer, not to experiment harder.