Has any plumbed a La Marzocco Linea Mini using the BWT filter system from Whole Latte Love - Page 4

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bluesman
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#31: Post by bluesman »

Jasper_8137 wrote:I have had some issues with the line pressure and pump pressure settings. Per the folks at La Marzocco home, mainline pressure should be at 3 barr and pump pressure should be at 9 barr while running. With the line pressure I'm at ~ 10 barr. If I adjust the expansion valve to get to 9 barr, water pours out of the valve and makes a horrible noise when brewing. This goes away if I tighten the valve to get it back to about 10. I was able to decrease line pressure to about 2 and achieve 9 barr at the pump. I'm a bit nervous though that not enough water is making it to the machine at the lower line pressure.
The narrowest cross-sectional area in your water flow path determines maximum volume flow. Pressure is not a flow constraint at the levels to which we regulate it. And as your water line is feeding your filter at somewhere between 5 and 7 bar, there's plenty of force to move as much water as your regulator can pass. Pressure is distributed equally in all directions through a fluid and is measured as force per square area (1 bar = 14.7 psi at sea level) - so the pressure is the same through a 1 mm orifice as it is through a 1 meter orifice as long as there's sufficient force on the source. What changes are the speed of flow and the maximum volume that can flow through the opening in a given period of time. Your pump will suck sufficient water to reach brew pressure whether it's being fed at 2 bar or 3 bar, as long as your lines and connectors are of sufficient caliber to pass the needed volume.

I'd suggest loosening the tie securing the loop in your feed line. Strain relief is great - but you want some flexibility so the water line can dissipate the occasional pulse that might lead to loosening over time if the lines are all tightly held down. You can use something stretchable like a tiny bungee cord, or you can loop a plastic tie wrap just firmly enough to hold the crossing hose segments together without binding them tightly. If they're closely approximated, you don't need to hold them together at all. Just make sure that the hose is neutral (i.e. that it didn't twist as you tightened the nut) so that it's not putting counterclockwise torque on the connector. That's a common cause of leakage - it can unscrew its thread from the male mate over time if it was really torqued during installation.

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