By "A full cup," do you mean one full liquid measure cup (as in, 8oz), or a demitasse? While it is normal for some water to come through during the purge, seeing a significant increase in the amount of water typically suggests that the boiler is either over-filling or running too cool. As the machine determines the proper fill level by the conductivity of water, the former can be caused by low-mineral content water (reverse osmosis processed, distilled, or otherwise *heavily* filtered water can all reduce the mineral content to the point where it can't conduct electricity correctly). Alternatively, you may want to consider removing and cleaning the water level probe to ensure that it is clean and able to conduct properly--any surface scale on this part could result in an altered fill level (typically, overfilling). Finally, you can always try adjusting the pressurestat to up the boiler's operating temperature slightly. I would take this step carefully as it would have a direct effect on the brewing temperature of your machine--you can always try measuring the in-cup temperature of a few 2oz pulls, comparing them against the new Compare-o-matic. If the shots are below temperature, you can safely increase the steam pressure slightly. if the shots are on target, you'll likely see a decline in brew quality, and would be trading some additional water during the purge for a change in the drink itself. Let us know if you have any questions about how to attempt any of these processes!