Flow restriction via mains tap?

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#1: Post by Timovzl »

I thought it might be fun to experiment with Michael Cameron's low-pressure recipe (https://strivefortone.com/2016/05/18/th ... re-rehash/), but it calls for reducing the water debit. My Ascaso Baby T Plus does not offer flow control, so I've been thinking:

Could one restrict the water debit using a tap on the mains connection?

Is this fine, or could the reduced water input be a problem for the rotary pump or other components?

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#2: Post by JRising »

Intentionally cavitating the pump would not be good for it, no. Never allow the pump to be starved for water.

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#3: Post by Pressino »

Not only that, but throttling the pump would not do the same thing as placing a "flow control valve" just above the brew chamber. The pump is designed with a pressure regulator to deliver water at a particular maximum pressure setting (measured at the output side of the pump). For flow/pressure "profiling" you want to adjust the flow/pressure as close to above the brew chamber as possible. Think about the layout of the water distribution in espresso machines and you will see why trying to adjust brew flow/pressure by throttling at the pump input will not achieve what you want.

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#4: Post by Jeff »

First, kudos to taking on exploring extraction space. I have found many rewards moving away from traditional parameters.

On "water debit" or basket-fill rate, on most machines it is typically limited by a tiny hole in the path before dispersion block. On commercial machines there are sometimes different choices, perhaps 0.6 and 0.4 mm. The smaller the hole, the lower the flow. Also, the lower the pressure difference across the hole (roughly pump-to-basket), the lower the flow. With a home machine you probably don't have huge fill rate to start with. Dropping to 6 bar or so will lower that a bit as well. The target in the paper of around 200-280 g in 30 seconds seems around what I'd expect from a home machine without changing things.

Since you're applying the ideas of that post rather than trying to replicate the experiment, I would:

* Drop your pump/OPV pressure to 6 bar (or your choice)
* Use your usual coffee, basket and dose
* Tamp so the bed pushes back a bit but not hard, if you don't have a force-indicating tamper
* Tune by taste