If only one tap suddenly has much lower pressure while others in the house are fine, the problem is likely local to that fixture. It might mean a partially blocked aerator (the little mesh at the tip), a clogged internal cartridge, or some debris stuck in the supply line to that tap.

Hard water can cause mineral deposits to build up inside taps over time. Loosening and cleaning the aerator often fixes minor issues. If cleaning doesn’t help, there could be a problem with the tap’s internal parts. In that case, servicing or replacing the tap might be needed.

Less commonly, a kinked flexible hose under the sink or basin can also reduce flow. Checking that hose for bends or damage is another quick step.

The key point is that a local pressure drop usually doesn’t mean a whole-house supply issue. It’s your hint to focus attention on that one fixture instead of worrying about the main line.