La Marzocco GS3 AV Aggressive Taste After Plumbing

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Cristiano

#1: Post by Cristiano »

Hello Community HB! I made a water connection (without using the tank) to my La Marzocco GS3. The pressurizing pump and the filters were 40cm below the machine and, at the end of the filtering system, I placed a pressure regulating valve which is measuring an average of 3bar, but the manometer of the machine reads 4bar. I would like to know what would be the ideal place for a more accurate reading? and the actual value would be 3bar?
Thank you very much for your contribution!

Best Regards!

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Jake_G
Team HB

#2: Post by Jake_G »

Seems like you are measuring in the correct place.

Is the GS/3 measuring 4 bar when cold, or hot?

You can't rely on the panel gauge to tell you much of anything useful when powered on and sitting idle, as it reads directly off the coffee boiler. Since there are check valves between the water inlet to the pump and the boiler, any heat applied to the boiler will cause the pressure to increase.

If the reading is cold, my guess is that ond of the two gauges is inaccurate.

Cheers!

- Jake
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Cristiano (original poster)

#3: Post by Cristiano (original poster) »

Thanks for the feedback Jake! The reading I take on the coffee manometer is with the machine cold. I'm not sure how to make this adjustment accurately. My coffees have a super aggressive taste, a mixture of acidity with bitterness and a horrible aftertaste. I'm trying to find out what's going on. I am using a water/reverse osmosis and then remineralized according to Dr. Rpavlis.

Best Regards!

katkat
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#4: Post by katkat »

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Jake_G
Team HB

#5: Post by Jake_G »

Cristiano wrote:My coffees have a super aggressive taste, a mixture of acidity with bitterness and a horrible aftertaste. I'm trying to find out what's going on.
This is just since plumbing?

What's your pressure whilst brewing?
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Cristiano (original poster)

#6: Post by Cristiano (original poster) »

Right at the beginning of the water connection, I didn't feel much difference, but I've been having this difficulty for 1 month. My current pressure is 9bar, measured with the water discharged in the group, without using the filter holder. Another strange thing is that the grinding in the Niche needed to be much coarser for the extraction to happen without choking. Before, I used the setting of 16 - 18 in Niche, or even less, depending on the roast of the coffee used, today it's an average of 22 - 25.

Thank you very much for the contributions.

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Jake_G
Team HB

#7: Post by Jake_G »

What coffee are you using?
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Cristiano (original poster)

#8: Post by Cristiano (original poster) »

I'm using some coffees from a roaster in Munas Gerais (Brazil) that I've bought many times, with a medium roast. I've already modified the coffees 3 times, but it doesn't matter, the aggressive flavor remains there.

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Jake_G
Team HB

#9: Post by Jake_G »

Acidity and bitterness with a harsh aftertaste is often something I would attribute to massive channeling, wretched coffee or a filthy machine.

The change in grind setting is a really interesting phenomenon. Have you cleaned the burrs and verified nothing is loose inside the Niche?

Next, I'd verify that brew temperature is accurate. Without a Scace device, you can raise the brew temperature until you get flash boiling and verify that the display reads your local boiling temperature when this occurs. What temperature does your display show? Have you tried increasing/decreasing temperature by 2 degrees or more to verify you can influence the flavor as expected? Cooler shots should taste more sour/acidic, hotter shots should swing from bright/acidic to flat and bland to bitter and burnt.

What does your puck prep look like? Are you using a bottomless for evaluation of your extraction? I'd want to be certain you aren't experiencing chanelling or some other sort of wildly uneven extraction.

Lastly, you can try the horrible preinfusion. The goal would be to minimize the amount of pressure built at the puck before the pump off time, but sometimes something like 2s on, 5s off can make a big difference, even though I despise this approach.

Cheers!

- Jake
LMWDP #704

Cristiano (original poster)

#10: Post by Cristiano (original poster) »

Hi Jake, nice to hear from you, including so many possibilities for solving the problem! Come on: I clean the machine with Cafisa (detergent), including filters and filter holders, every week, very rarely going beyond that time. Regarding channeling, I believe it happens. After several coffee dispensing/leveling tools in the filter, I have lately been using the WDT (directly in the filter) with acupuncture needles fixed in a wine cork. I have a Naked filter holder and, from my analysis, I don't notice anything remarkable about the plumbing, but when I analyze the coffee in the filter after extraction, I almost always observe some small holes on the right side of the filter. I'm going to perform the temperature test you suggested, in this case the water comes out of the boiling group, comparing this moment with the boiling temperature of my region, is that it? The temperature I have set is 90°C on the display and in the coffee boiler it is 91.4°C.

Best Regards,

Cristiano.