As with any espresso machine, the primary cause of leaks is limescale buildup on a fitting or part, which then malfunctions. The OPV can leak if it stuck open with limescale or particles. The internal spring (not sold separately) can be compromised, as well. One can try to descale the grouphead only with a blind disc in the portafilter. Please make sure to remove any water treatments from the reservoir.
If a replacement is required, then the part in question may be the brass valve assembly.
(Check to make sure this part if it goes to the reservoir or the drip tray and look for any leakage)
Sometimes, the bleeder valve or safety valve will leak to a tube to the left side of the drip tray. This is a multi-functional item.
Some have tried to take the ends apart and descale the internal pieces with success. However, the success rate is low once limescale has impacted this part.
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