If your portafilter is constantly spitting water or coffee grounds, it could be due to a few different reasons. The most common reason is that the grind size is too fine. If the grind is too fine, the water will have difficulty flowing through the coffee grounds and will often result in a clogged or blocked portafilter. Another reason why your portafilter may be spitting is because the basket isn't tamped properly. If the coffee grounds aren't evenly tamped down, water can easily seep through and cause the portafilter to spit. Finally, if your machine's brew pressure is too low, it can also cause your portafilter to spit coffee or water.