How Do Different Water Flow Rates Affect Pour-Over Coffee Brewing? How to Measure Water Pouring Speed?

Large flow and small flow—these are not just recurring topics in FrontStreet Coffee's articles, but also terms frequently mentioned by coffee baristas when discussing brewing! However, many friends have some misconceptions about the definitions of these two concepts. Today, FrontStreet Coffee will share what constitutes a large flow and what constitutes a small flow!

Misconceptions About Water Flow

Many people's misconception about water flow lies in thinking: "small flow means the poured water is gentler, with weaker stirring force; large flow means a rugged, impactful water stream!" But in reality, large and small flows refer to the speed of the water flow—how much water is poured per second during brewing. The water flow impact mentioned above is mainly related to brewing techniques and pouring height. A small flow can also have strong penetrating power that makes the coffee grounds tumble, while a large flow can also be poured very gently.

Secondly, as described in yesterday's article from FrontStreet Coffee, the kettle spout creates differences in water flow! With the same amount of water and the same pouring angle, different types of spouts can create variations in water volume. Water poured from narrow spouts is generally smaller in volume, while water from wide spouts is generally larger in volume. Therefore, when discussing water flow issues, differences in spouts often lead to communication gaps.

At this point, some friends might ask: "How can I measure my water flow speed?" It's actually quite simple. Many electronic scales now have speed measurement functions that can measure the flow rate while recording the weight.

But what about friends who haven't purchased such electronic scales with speed measurement functions? No worries! FrontStreet Coffee will now share a method to measure your water flow speed!

How to Measure Your Water Flow Speed

First, we still need to prepare an electronic scale—a regular one will do, it doesn't need to have speed measurement functionality! Then, place any container on the electronic scale. Next, we pour water using our usual pouring method and start timing.

Time for ten seconds, then divide the amount of water poured during these ten seconds by 10, and you'll get your pouring speed per second! FrontStreet Coffee uses a copper kettle modified with a hawk spout, and with a vertical water stream, the minimum flow rate is 2.2ml/s, and the maximum flow rate is 9ml/s. Then switching to a Kalita copper kettle with an elephant trunk spout, with a vertical water stream, the minimum flow rate is 4ml/s, and the maximum flow rate is 12ml/s. In multi-stage brewing, people generally don't use a single water flow throughout, because the coffee brewed this way isn't necessarily bad-tasting, but rather not as delicious. So, friends can match and combine according to their own brewing methods and the effects brought by large and small flows.

What Different Effects Do Large and Small Flows Have?

You can see their effects very intuitively just by brewing a pour-over coffee using large and small flows respectively! The brewing parameters are as follows: using Guatemala New Eastern Geisha beans, ground to EK43 setting 9.5, with a coffee-to-water ratio of 1:15 (15g beans, 225ml water at 92°C), using a three-stage brewing method.

First, brewing time: Using only small flow throughout took 2 minutes and 5 seconds, while using only large flow throughout took 1 minute and 57 seconds. From this, we can see that when the brewing parameters are the same, brewing with small flow takes longer than with large flow!

Second, coffee bed height: What we often call raising the coffee bed means that when the drainage rate is lower than the pouring rate, the position of the coffee bed will be raised. The larger the difference between drainage rate and pouring rate, the faster the coffee bed rises. Therefore, combining with the first point, we can know that using small flow to raise the coffee bed will be slower, while using large flow will be faster.

And when we talk about raising the coffee bed, it generally refers to using large flow to create a gap between drainage rate and pouring rate, allowing the coffee bed to be raised in the shortest time possible.

Third, flavor performance: Due to the slower drainage rate of small flow, coffee brewed entirely with it will taste richer with concentrated flavors, mainly because the extraction time is longer and there are more stirring instances. Meanwhile, large flow drains faster, so coffee brewed entirely with it will have more prominent and clear flavors, but compared to coffee brewed with small flow, it will be relatively lighter and thinner.

When to Use Large Flow and When to Use Small Flow?

Regarding the choice between large and small flows during brewing, FrontStreet Coffee suggests: "be flexible." This is mainly because the choice depends on the brewing method used, the current state of the coffee bed, and the brewing time. If you're used to using large flow when brewing, then when the following situation occurs during the brewing process, it's best to adjust to small flow!

If the drainage rate is much faster than usual: The water level should be in the middle of the filter cup at this time point, but due to overly coarse grinding, the drainage is too fast and about to finish! In this case, you need to switch to small flow to extend the extraction time and avoid under-extraction.

If you're used to using small flow when brewing, then when the following situation occurs during the brewing process, it's best to adjust to large flow!

If the extraction time is too long: Although long extraction can yield more coffee substances, it easily extracts bitter compounds! If blockage occurs during brewing or if the grinding is too fine causing slow drainage, you need to switch to large flow to speed up drainage and reduce over-extraction.

When you need to raise the coffee bed: Small flow pours less water, creating a smaller gap with the drainage rate, so raising the coffee bed will be slower. Therefore, when we need to raise the coffee bed, it's best to use large flow in the stage after blooming to quickly raise the coffee bed, allowing all coffee grounds to receive ample and even extraction!

Of course, when FrontStreet Coffee says to increase/decrease the water flow, it means adjusting based on your original flow rate. The fluctuations during pouring should not be too drastic—small adjustments are sufficient~ For example, if FrontStreet Coffee uses a flow rate of 5ml/s during brewing, and we need to increase the flow, raising it to 6-7ml/s is enough, no need to push it to extremes like 8-9ml/s~

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FrontStreet Coffee

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