I am not sure I have much to impart on the subject, except to say that in my experience with Alfa Laval purifiers, there is always a perfectly good explanation for malfunction.
In this case I am sure you've taken the unit apart. I am not familiar with this particular unit, but a careful inspection of the orings should be carried out. Perhaps the bowl is not closing properly, so before you even take anything apart check your water pressure. Sometime operating water has a filter, which gets clogged up giving you lack of sealing pressure. Kinked hoses have also been a problem for me in the past.
Depending on your machine and its control panel, you can run a full diagnostic on the water system, using a stopwatch and measured bucket. Look in the manual for specific instruction.
Another reason for the bowl not closing might be the springs, over time they get compressed and need to be replaced. Check the manual for specs, I've have had to replace a few set of spring to correct this type of issue.
Like I said there is usually a very simple and obvious problem with Alfa Laval machines, so start with the outside variables, in particular operating water, and air too. Is this a new problem? Gradual? Is your back pressure okay? is the gauge accurate?
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