When used in conjunction with a one way valve a thermal expansion or accumulator tank will help solve the age old problem of pressure fluctuation on an espresso machine. The principle is simple. The tank will hold two gallons of pressurized water, prior to the pressure pump located in the espresso machine. What this does is create a constant pressure feed of water to the pressure pump. This is important due to pressure fluctuations caused by multiple devices drawing water from a single source. We are happy to discuss how this works and will be providing additional images that show installation processes. If you have any questions, please call Terry Z 800-459-5594 x 103