What Causes Water Accumulation in the Portafilter Basket After Espresso Extraction and How to Solve It

A friend with an espresso machine asked FrontStreet Coffee, "I've recently encountered a phenomenon during espresso extraction. After extracting the coffee, when I remove the portafilter, I notice water pooling in the filter basket, and the extracted puck isn't in a complete state—it's soggy?" He then added, "At first, I thought the coffee grounds were too fine, so I adjusted the grinder to a coarser setting, but there's still water pooling. I'm completely puzzled?"

Under normal circumstances, the espresso puck after extraction should be relatively dry, and the extracted coffee puck should form a relatively complete, solid cake. If the coffee puck appears soggy and soft, or even shows signs of water pooling on its surface, this is not a normal phenomenon and requires identifying the cause and making corrections.

Coffee Grounds Too Fine

Just like the friend who posed this question, his first thought upon noticing water pooling was, "Is there an issue with the coffee grind size?" When coffee grounds are too fine, water passes through the coffee layer more slowly. At the end of extraction, some water may not have had enough time to pass through the coffee layer. When the puck contains too much water, it appears in a soggy, muddy state, and in severe cases, water pooling occurs.

However, under normal circumstances, it's quite easy to determine if coffee grounds are too fine, because overly fine grounds cause the espresso to flow slowly, resulting in a longer extraction time. Therefore, this cause is very easy to identify.

Stale Coffee Beans

But there's one exceptional situation where it's difficult to detect if water pooling is caused by overly fine coffee grounds: when the coffee beans aren't fresh. This situation often occurs among home brewers with lower consumption volumes. Generally, with typical daily espresso consumption, a bag of espresso beans might last for a month, during which the carbon dioxide content in the coffee beans continuously decreases.

When coffee beans contain carbon dioxide, during extraction, hot water first moistens the puck, and the coffee grounds expand to fill the gaps between particles. If the coffee beans contain little to no carbon dioxide, they won't expand, and with the same grind size, espresso will flow relatively quickly. To compensate for insufficient extraction time, one would normally adjust to a finer grind. In this case, it's possible that coffee grounds become too fine, leading to water pooling.

Puck Too Far From the Shower Screen

FrontStreet Coffee will briefly explain the espresso extraction process. When the extraction button is pressed, the group head releases water at 9 bar pressure. After passing through the shower screen, this water divides into several streams that evenly extract substances from the coffee puck. When the extraction button is turned off, the pressure relief valve opens, creating backpressure that draws excess water from the coffee puck back through the pressure relief valve for discharge.

Different models of filter baskets can accommodate different amounts of coffee grounds. Too much coffee will stick to the shower screen, while too little will be too far from it. When the distance between the coffee surface and the shower screen is too large, some water may not be drawn back by the backpressure, remaining in the filter basket and forming water pools.

Therefore, to determine if the coffee amount is appropriate, you can tamp the coffee firmly and observe if it just reaches that indent line. If it's quite far from that line, it means there's not enough coffee; if it exceeds that line, it means there's too much coffee.

Insufficient Pressure

This cause is more common in some home espresso machines where the pressure during extraction isn't very stable. While maintaining higher pressure in the early stages, the pressure drops in later stages, resulting in insufficient backpressure during the final phase, which leaves water pooling in the filter basket.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473