If only one tap has low pressure, the cause is usually in or close to that tap, rather than the main water supply. Common reasons include a blocked aerator, a partly closed isolating valve, a worn or clogged cartridge, or a kinked or restricted supply hose.
Because the rest of the home is working normally, the problem is usually easier to narrow down. Checking whether the hot side, the cold side or both are weak is a good place to start.
The Aerator or Spout
Many taps have an aerator, a small mesh at the end of the spout that mixes air into the water. Over time, limescale and grit can collect in it and restrict the flow. This is one of the most common reasons a single tap becomes weak.
If the flow has dropped gradually, or the water sprays unevenly, the aerator may be partly blocked. A weak tap does not always mean this, though. Some taps are also designed with flow limiters, so a new tap may feel weaker than an old one even when nothing is wrong.
Valves and Hoses Under the Tap
Taps are often fed by flexible hoses with small isolating valves. If a valve has been partly closed, perhaps during earlier work, the flow to that tap may be reduced. A kinked, twisted or damaged hose can also restrict the water reaching the tap.
If the tap has hot and cold supplies, check whether only one side is weak. This can point to a valve or hose on that side.
Inside the Tap
Worn or clogged parts inside the tap, such as a cartridge or washer, can restrict the flow. Mixer taps may be weak on one side if the part that blends hot and cold water is worn or scaled.
In this case, the tap may need repair or replacement rather than any change to the wider plumbing. Our tap repair page explains how faulty taps are assessed.
When It May Be More Than the Tap
If a tap is weak but other taps on the same pipe run are also slower than they used to be, there may be a restriction in the pipework serving that part of the home. Older pipework can sometimes build up deposits inside, although this varies.
A tap that is weak only when another tap or appliance is running may be affected by how the pipework is shared, rather than by a fault in the tap itself.
Avoid taking the tap apart or forcing stiff valves. Note when the problem started and whether it affects hot, cold or both. Our page on low water pressure explains how pressure and flow problems are assessed, whether they affect one tap or several.
If one tap in your Poole home has become weak, a plumber can check the tap and its supply and explain what may be needed to put it right.