Low water pressure in a specific faucet, in this case, your kitchen sink, can be caused by a few different factors. Since you mentioned that all other faucets have good water pressure and the pipes are relatively new, the problem is likely localized to the kitchen sink itself. Here are some common reasons why you might experience low water pressure in just one faucet:
Clogged aerator: The aerator is a small mesh screen at the end of the faucet that helps regulate the water flow and prevent splashing. Over time, minerals and debris can build up and clog the aerator, reducing water flow. Unscrew the aerator and clean it thoroughly or replace it with a new one.
Partially closed shut-off valve: Each faucet has its own shut-off valve, and it's possible that the valve supplying water to the kitchen sink might not be fully open. Check the valve located under the sink and ensure it is fully open.
Obstructed or damaged water supply line: There might be an obstruction or damage in the water supply line that is connected to the kitchen sink. Check for any kinks, bends, or visible signs of damage in the supply line and replace it if necessary.
Faulty pressure regulator: Your home might have a pressure regulator that controls the water pressure throughout the house. If it's malfunctioning, it could be affecting only the kitchen sink. A plumber can test and replace the pressure regulator if needed.
Pipe corrosion or blockage: Despite having copper pipes, corrosion or mineral buildup can still occur over time, especially in older homes. If there's a blockage or corrosion in the specific pipe supplying water to the kitchen sink, it could be restricting the flow.
Plumbing vent issues: If there's a problem with the plumbing vent system, it could cause airlocks or reduced water pressure in some faucets. However, this is less likely to be the issue if the other faucets are functioning properly.
Defective faucet cartridge or valve: The kitchen faucet itself may have a faulty cartridge or valve that is causing the low water pressure. In this case, you might need to replace the faucet or specific internal components.
To identify and fix the exact cause of the low water pressure, you can start by checking the aerator and the shut-off valve under the sink. If those are not the culprits, it's best to call a professional plumber to inspect the kitchen sink's plumbing and diagnose the issue accurately. They will be able to provide the most suitable solution to restore the water pressure in your kitchen sink.