Low Water Pressure in the Shower: Causes and Fixes

Step 1: is it only the shower?

Open the bathroom basin tap and the kitchen tap. If they run normally and only the shower is weak, the problem is in the shower: the head, the hose or the mixer.

If everything is weak, go to step 4.

Step 2: clean the shower head

Unscrew the head from the hose. Look at the holes: white or grey deposits are limescale.

Soak the head in white vinegar or a limescale remover for a few hours, then rub the rubber nozzles with your fingers or a soft brush. Many heads also have a small filter where they screw onto the hose — clean that too.

While it is off, run the hose alone. If flow from the hose is strong, the head was the problem.

Step 3: the hose and the mixer

A kinked or collapsed hose reduces flow. Replace it if it is old.

Mixer valves have small filters at their inlets, which fill with grit and scale. Thermostatic mixers are particularly sensitive: a partly blocked cartridge gives weak or unstable water. Cleaning or replacing the cartridge restores the flow.

Step 4: low pressure only on hot water

With an esquentador, scale in the heat exchanger or a clogged inlet filter reduces hot water flow — and may stop the heater lighting. With an electric tank, check that the valves around it are fully open.

A heater that needs servicing often shows up first as weaker hot water. See no hot water in your apartment.

Step 5: low pressure everywhere

Check that the main water valve is fully open — after works or a meter change it is sometimes left half closed.

Ask a neighbour. If they also have weak water, the cause is in the building or the street supply: a pressure issue, works nearby, or a problem with the building's pumps if it has them. Tell the building administrator or the water company.

If only your flat is affected, old galvanised iron pipes narrowed inside by rust and scale are a classic cause in older Lisbon buildings. See pipe replacement and buying an old flat: plumbing checks.

Top floors and pressure pumps

On upper floors of taller buildings, mains pressure alone may not be enough. Buildings often have a pressure pump system, and when it fails, the top floors notice first.

Some flats add their own small booster pump. It can help, but it must be sized and installed correctly — and it cannot fix pipes that are blocked with rust.

Pressure versus flow: why it matters

Pressure is the force pushing the water; flow is how much comes out per minute. Old pipes narrowed by rust can have normal pressure at the meter but poor flow at the taps.

A simple test: time how long it takes to fill a 10-litre bucket from the shower hose without the head. Much more than a minute and a half suggests restricted flow somewhere between the meter and the shower.

Pressure-reducing valves

Some flats have a pressure-reducing valve after the meter, installed to protect the pipes from high street pressure. If it is set too low or has failed, the whole flat has weak water. Adjusting or replacing it is a quick job — do not tamper with it without knowing what it does.

Booster pumps: when they help

A booster pump can help on top floors or where mains pressure is genuinely low. It must be sized correctly, installed with the right valves, and it should not be connected in a way that pulls water from neighbours' supply. It will not fix narrowed pipes or blocked shower heads.

Old pipes: the long-term fix

If the whole flat has weak flow and the pipes are old galvanised iron, cleaning heads and valves only helps a little. Replacing the supply pipes restores full flow — and usually ends the rusty water and the leaks at the same time. See pipe replacement.

For simpler causes, repairs start from 60 €.

Frequently asked questions