Turning on the tap and watching the water dribble out instead of flowing full force is frustrating. Several conditions are responsible for deficient water flow, and some are easier to repair than others. Once you have eliminated the easy problems, though, you may need to call a plumber. The problems that are difficult to repair may warn you of something seriously wrong that needs immediate attention.
Debris in the water line
Mineral deposits can clog up a water line, especially if your water is hard or rich in minerals. The first and easiest place to look for obstructions is the aerator screen. Unscrew the aerator, and clean the screen thoroughly. You should also examine the tap supply hoses. Unscrew the connections to the tap, and turn on the angle stops, or shutoff valves, under the sink. If water flows, your tap needs cleaning, or the valve may need adjusting. If water doesn't flow, the problem is further back in the water line.
If your house was built in the first part of the 20th century, you may have galvanised steel water pipes, which are no longer widely used because the lines develop internal corrosion over time that gradually constricts the water passage and inhibits flow. You can confirm this condition by visually examining your galvanised pipes. If you see signs of corrosion on the outside, the inside is probably corroded as well. While you can replace a damaged section of galvanised pipe, choose a retrofit copper if you see signs of extensive corrosion.
Kinked water pipes
Sometimes the problem is as simple as a kinked water line. Inspect the flexible connectors between the angle stops and your tap. If the connectors are too long or are winding awkwardly around the drain pipes, kinks can develop, especially if the connectors are corrugated metal instead of reinforced plastic. This problem is one of the easiest to diagnose, and you can correct it by simply replacing the hoses. Kinking is especially likely to occur if your tap is connected to the angle stops with solid copper tubing.
Faulty pressure pump
If you have deficient flow from several or all of the fixtures in your house, and you can rule out constricted pipes, insufficient pressure in the water lines is likely the problem. If you have a well, the jet pump that pressurises your water tank may not work correctly. To confirm this, look at the pressure gauge on the tank, which should read about 60 psi. If the reading is significantly less than this, the pump may not be cycling on correctly. Replace the pump if this is the case.
If you can rule out any other cause for low pressure at your tap, you may have a leak in the water line. Even though the leak may be a significant one, it may not be obvious if it is buried in the walls or underground. Don't let this situation persist. If you can't find the leak, call a plumber immediately. Leaking water can damage the structure of your house and undermine the foundation.