water is leaking from the bottom of the machine onto my counter, mostly when it's brewing

Diagnosis

The Keurig K-Supreme Plus SMART typically experiences bottom-leaking during the brew cycle due to a failure in the pressure-seal integrity or a breach in the internal fluid path. Because this model utilizes a high-pressure pump to force water through the K-Cup, any microscopic crack in the internal tubing or a degraded O-ring on the reservoir valve will result in water escaping. When the pump engages, it creates a surge of pressure; if the seal at the base of the water reservoir is worn or if a piece of debris (like a stray coffee ground or mineral scale) is trapped in the valve seat, water will bypass the intake and leak directly into the chassis, eventually pooling on your countertop. To confirm the exact source, you must perform a "dry-run" isolation test. Remove the water reservoir and dry the base of the machine completely with a microfiber cloth. Fill the reservoir and place a single sheet of dry paper towel on the counter directly beneath the reservoir intake. Run a medium brew cycle. If the paper towel wets immediately upon the pump starting, the leak is located at the reservoir valve or the intake port. If the water appears only after the coffee begins to flow into the cup, the leak is likely coming from the internal brew head assembly or the exit needle seals.

How to Fix It

If the leak is originating from the reservoir interface, follow these steps to restore the seal:

1. Power down the machine and unplug it from the wall outlet to prevent electrical shorts.
2. Remove the water reservoir and inspect the rubber gasket (the O-ring) at the bottom of the tank. Check for any signs of "flattening," cracking, or mineral buildup.
3. Use a cotton swab dipped in white vinegar to clean the valve seat inside the machine's base where the reservoir locks in. This removes calcium deposits that prevent a flush seal.
4. Inspect the reservoir for hairline fractures. Fill the tank and let it sit on a dry surface for 30 minutes; if you see droplets, the plastic housing has a stress fracture and the reservoir must be replaced.
5. If the seal is intact but leaking persists, perform a "Hard Reset" of the internal valves: Fill the reservoir, lock it in firmly, and run three "Water Only" brew cycles (no K-Cup) at the largest cup setting. This flushes any trapped air pockets or debris that may be causing the valve to seat improperly.
6. Ensure the drip tray is seated perfectly flush; a misaligned tray can sometimes redirect internal splashes back onto the counter, mimicking a leak.

If That Didn't Work

• Descale the Internal Lines: Mineral buildup can create "micro-blockages" that increase internal pressure, forcing water past seals that would otherwise hold. Use a commercial descaling solution or a 50/50 mix of white vinegar and water. Run the full cleaning cycle and then three rinse cycles to ensure all acidity is removed.
• Inspect the K-Cup Holder Seal: If water is leaking from the top and dripping down the sides to the bottom, the needle seal is compromised. Check the puncture needle for bends or debris. Use a needle or a thin paperclip to clear any coffee grounds stuck in the exit needle.
• Check the Internal Tubing: If you are comfortable opening the chassis, inspect the silicone tubing connecting the pump to the brew head. Look for "pinhole" leaks or loose clamps. If a tube has slipped off its barb, you can re-secure it using a small zip-tie or a replacement hose clamp.
• Replace the Water Reservoir: If the leak is intermittent and occurs only when the tank is full, the plastic has likely warped. Replace the reservoir with an OEM part specifically for the K-Supreme Plus SMART model to ensure the valve pressure is calibrated correctly.

Heads Up

• Always use filtered water to prevent calcium scale from eroding the rubber gaskets and valves over time.
• Avoid overfilling the reservoir beyond the "Max" line, as this can put undue pressure on the bottom valve seal.
• Never use a generic "universal" water tank; the K-Supreme Plus SMART has specific valve tolerances that differ from the K-Cafe or K-Elite lines.
• If you notice a "metallic" taste accompanying the leak, stop using the machine immediately, as this may indicate a breach in the internal heating element or pump housing.