Diagnosis
The most likely cause is an overfull drip tray. The Classic Pro's drip tray has a small black plastic float that rises as it fills. When it's full, water overflows into the base of the machine.
How to Fix It
Empty the drip tray. Don't just glance at it—lift it out and pour it out completely.
- Remove the drip tray and the grate.
- Dry the area underneath the machine where the tray sits.
- Check the black float in the tray's hole; make sure it moves up and down freely and isn't stuck.
- Reinsert the tray. The leak should stop immediately.
If That Didn't Work
The leak could be from the over-pressure valve (OPV), which dumps excess pressure/water into the drip tray via a small tube. If that tube is disconnected, misrouted, or cracked, water will leak into the base. Unplug the machine, remove the top cover, and check the small silicone tube running from the OPV (near the pump) down towards the drip tray area.
Heads Up
Get in the habit of emptying the drip tray every day or two, not just when it looks full. Water in the base can lead to corrosion or electrical issues over time.