express water ro5dx leaking from somewhere under the sink, i see a small puddle. what do i check?

Find the source. Shut off the feed water valve and the tank valve immediately.

DIAGNOSIS: Loose connection, cracked housing, or faulty O-ring.

FIX:

1. Dry everything. Turn water back on briefly to spot the leak.
2. Check all quick-connect fittings. Push tubing in firmly until it clicks. A half-seated tube leaks.
3. Inspect filter housings. Tighten by hand only. Overtightening cracks the plastic.
4. Examine the drain line saddle valve connection on the sink drain. Ensure it's tight and the rubber seal is intact.

IF THAT DIDN'T WORK: The leak is likely from a component.

• Filter housing has a hairline crack. Replace it.
• Automatic shut-off valve diaphragm is failed. Replace the valve.
• Storage tank bladder is leaking internally. You'll see water from the air valve. Replace the tank.

HEADS UP: Water with high TDS (>500 mg/liter) is more corrosive. Over years, this can accelerate wear on metal parts in fittings. Use the recommended lubricant on O-rings during filter changes.