On Wed, 3 Jun 2009 14:21:15 -0700 (PDT), David
wrote:

Hi there,

Our 6 year old Siemens integrated dishwasher broke down and today it
got repaired, I came home from school and I found out that he replaced
the "pressure chamber", the old one was on the worktop.

I am interested to find out what that part actually does, so could
anyone explain please?

A piccy might help.

Without one my guess is it's the device that checks if the water has
reached the correct fill level.