La Marzocoo GS3 MP plumbing issue - pressure gauge pointer jumping

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#1: Post by ricky403 »

Update on 25 Nov 2022

My accumulator tank is arrived and I add it into the set-up with my Flojet. The gauge pointer jumping issue disappears :D Thanks for the hints and advice from Eric, Dan and Michael! Much appreciated!

Original Post on 24 Nov 2022
Hi, I'm new here. I find there are several topics about GS3 plumbing issues but none of them has mentioned the pressure gauge pointer jumping issue I have encountered. So I open this topic and seek your advice.

I change my GS3 from reservoir to plumb-in today. I use Flojet between the bottled water and GS3 to reduce the burden of the rotary pump in GS3. Both the pump and the bottled water are very close to the GS3 itself. My initial set-up is as follows:

3 Gallon bottled water - Flojet 5000 series pump (40PSI max) - braided hose come with GS3 - GS3.

When I opening the paddle and releasing the water from the brew group, the boiler pressure gauge pointer will go to 9 bar but the pointer will jumping rapidly around 9 bar as long as the paddle is on. When I start brewing with the portafilter on the brew group, both the pressure gauge pointer of the boiler and the brew group will have the same issue mentioned above (pointer jumping rapidly around 9 bar). In the mean time, the Flojet is working but in an "ON" & "OFF" cycle mode.

If I remove Flojet in the queue and just plumb-in directly from the bottled water through braided hose to the GS3, the pressure gauge pointer works fine. No jumping issue at all. I am confused because the Flojet is supposed to help and provide a constant pressure in the water line. This means the boiler in GS3 will be fed with water constantly and steadily. However, it seems not working and causing the gauger pointer jumping in my set-up. What I did was wrong in this set-up? How can I fix this with the Flojet in the queue? Please help and thanks in advance!


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#2: Post by EricC »

Check here :

Espresso Cart - Goodbye Plumbed In

It looks as though you need an accumulator to smooth out the Flojet pump pulses.

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#3: Post by HB »

ricky403 wrote:I am confused because the Flojet is supposed to help and provide a constant pressure in the water line.
A Flojet pump is basically a pressure switch and vibratory pump. When the pressure falls below its threshold, the pump turns on. Since it's a vibratory pump, it pulses. If you want to eliminate these pulses, get an accumulator. The pump will cycle less frequently and the vibration will be smoothed out.

Also from La Marzocco GS3 Pump Is Louder When Plumbed In:
HB wrote:Go to your local big box store and ask for a water heater expansion tank. Or, if you prefer something smaller, get a Shurflo accumulator. Google "RV Accumulator Tank" and it will lead you to plenty of options.

Image courtesy of
Dan Kehn

ricky403 (original poster)

#4: Post by ricky403 (original poster) »

Thank you so much for referring this post to me. My accumulator tank is on the way and will try if it could solve my pointer jumping issue :D

ricky403 (original poster)

#5: Post by ricky403 (original poster) »

Also thanks for your advice, Dan! I have my accumulator tank on the way so that I will try it first when it arrives.