01 Sept 2026
The shower has faded to a dribble, or the kitchen tap takes an age to fill a pot. Weak water pressure is one of those faults where the cause is usually easy to find and the fix is usually small, as long as you check things in the right order.
Start with one question, because the answer halves the problem.
Is it every outlet, or just one?
Walk round the flat and run each tap and the shower, hot and cold, one at a time. You are not fixing anything yet. You are sorting the fault into one of three groups.
- One outlet only. The problem is at that fitting.
- Only the hot side. The problem is at the water heater.
- Everything, hot and cold. The problem is upstream of your fittings.
Nearly every diagnosis follows from that answer.
If it is one outlet only
The usual culprit is the aerator, the small mesh screen inside the tip of the tap spout. It catches sediment, and in a flat with older pipework it clogs steadily until the flow narrows to a trickle.
Unscrew it by hand, or with a cloth and pliers if it is stiff, rinse the mesh, soak it if it is furred up, and put it back. This costs nothing and fixes a surprising number of weak taps.
If the aerator was clean, work back along the fitting.
- The isolation valve on the wall behind the fitting may be partly closed. They get knocked, and they get left half open after other work.
- The flexible hose underneath may be kinked around a cabinet edge, which chokes the flow.
- The showerhead may be scaled. Unscrew it and soak it, or take the face off and clear the holes.
- The cartridge inside a mixer tap can clog or fail, which usually shows up as weak flow on one side of the mixer only.
If only the hot water is weak
That takes the flat's supply out of the picture and puts the heater into it. An instant heater normally has an inlet filter, and it does the same thing an aerator does when it clogs. On a storage heater, weak hot flow can come from a valve on the unit or a restriction at its connections.
Note the difference between weak and lukewarm. Weak is a flow problem. Lukewarm at full flow is a heating problem, which is a different fault with different causes. If it turns out to be heat rather than pressure, our water heater repair page covers that side of it.
If the whole flat is weak
Check the main stopcock first, and check it properly. In most HDB flats it sits high up in the kitchen near the ceiling, or inside the service duct. Open it fully. A stopcock left half closed after other work in the flat is a common cause of whole-flat weak pressure, and it takes seconds to rule out.
Then ask a neighbour on your floor, and one on a different floor. If they are affected too, the cause is in the building rather than in your unit, and your town council or managing agent is the right first call. Tank cleaning, maintenance and works in the block all show up as a floor or a whole stack losing pressure at once.
If it is only your flat and the stopcock is open
Now it is worth calling someone, because what is left is the pipework.
Older galvanised pipe corrodes and scales from the inside. The pipe looks sound from the outside while the bore within it narrows year by year, and the flow drops so slowly that nobody notices until it is bad. Discoloured water at the same time is a strong hint. Repeated leaks along one run is another. Our pipe repair work covers repairing or replacing a corroded section, and we would far rather replace one bad run than sell you a whole re-pipe you do not need.
A failing or partly seized valve in the flat's own run does much the same thing, so that gets checked first, because it is the cheaper thing to be right about.
Pressure and flow are not the same thing
This is worth knowing, because it explains why a pump is not the automatic answer.
Pressure is the push behind the water. Flow is how much actually comes out of the opening. A restricted pipe or a clogged screen kills the flow while the pressure behind it is unchanged. So fitting a pump before finding the cause is a poor move: if the restriction is a scaled pipe or a blocked aerator, the pump simply pushes harder against the same obstruction, and you have paid for equipment that hides the fault instead of clearing it. Find the restriction first.
When to call a plumber
Call when the aerators are clean, the stopcock is fully open, the neighbours are fine and the flat is still weak. Call sooner if the pressure dropped suddenly rather than fading over months, because a sudden drop can mean water escaping before it ever reaches your taps. There are more short answers on pressure and stopcocks on our FAQ page.