Weak showers, taps that take an age to fill, and appliances that will not work properly are all signs of a water pressure problem.
A sudden drop and a gradual decline over years point at different things. Start by working out which you have, and whether it is even your property.
If it is the pressure gauge on your boiler that has dropped, rather than the water at your taps, that is a separate problem with its own causes. Our guide to a boiler losing pressure covers it.
Is it you or the mains?
Ask the neighbours. If they are affected too, it is a mains supply issue and your water company needs to know. Southern Water covers most of West Sussex.
Check the outside tap. If pressure is low there, before it reaches any of your internal pipework, the problem is upstream.
Check every tap. Whole house means a supply or main pipe issue. One tap means a localised blockage. Hot only means the boiler or cylinder.
Call the water company and ask about planned works in the area.
If the neighbours are fine but your whole house is affected, the problem is most likely on your side of the boundary.
Water companies are responsible for supply up to your property boundary. Everything inside that, including the pipe running to the house, is yours.
What you can check yourself
A partially closed stopcock. Usually under the kitchen sink, and it can be knocked partly closed by accident. Turn it fully anticlockwise. This solves a surprising number of cases, particularly after any recent plumbing work.
Blocked tap aerators. The mesh filter in the tap spout clogs with debris and scale. Unscrew it, soak it in vinegar, rinse and refit. Replace it if it is damaged.
A limescaled showerhead. If only the shower is weak, that is almost always it. Soak overnight in white vinegar and scrub the holes clear. A shop-bought descaler also works, and a badly scaled head can simply be replaced.
What needs a plumber
If the simple checks have not helped, the cause is usually one of these, and each needs a plumber to diagnose properly.
A leaking supply pipe, often underground. Signs are damp patches, a jump in your water bill, or a hissing sound. Run the water meter test: note the reading, use no water for two hours, and check it again.
Corroded or scaled pipework. Common in older properties, particularly with original lead or galvanised steel. Internal build-up restricts flow progressively over years. Where it is bad, the answer is replacing the pipe.
A faulty pressure reducing valve. These are common in high-pressure areas. If the property has one, it can fail or drift out of adjustment, and sometimes it only needs adjusting. Usually causes a sudden change rather than a gradual one.
Shared supply problems. Some properties share a supply pipe with neighbours. When they draw water, your pressure drops. The fix is a dedicated supply or a pump.
Pressure against flow rate
These get confused constantly and they need different solutions.
Low pressure means water comes out weakly even with only one tap running. Caused by mains supply, pipe restriction, blockage or a leak.
Low flow rate means pressure is fine alone but drops when several outlets run. Caused by undersized pipework, a shared supply, or a combi boiler at its limit.
The solutions
The right fix depends on the cause, which is why the diagnosis comes first.
A booster pump raises pressure throughout the property where mains pressure is genuinely low.
A supply pipe upgrade, replacing a narrow or corroded pipe with modern 25mm MDPE, transforms flow in older properties.
Leak detection and repair, which is worth doing properly rather than excavating hopefully. Professional leak detection can often find a leak without major excavation.
A pumped shower if only the shower is the problem, which avoids re-plumbing the house.
What pressure should you have
Water companies must provide a minimum of 1 bar at your property boundary.
- 1 bar: the legal minimum, and it will feel weak
- 1.5 to 2 bar: good for most homes
- 2 to 3 bar: strong
- Over 3 bar: may need a pressure reducing valve to protect appliances
A gauge that screws onto an outside tap costs ten to twenty pounds and tells you exactly where you stand before you spend money on a solution. If you would rather not buy one, we can test it during a visit.
Frequently asked
Why is pressure fine in the morning but weak in the evening?
Your supply cannot keep up with peak demand. In the evening more people in the area are using water at once and mains pressure drops. Common with shared supply pipes or undersized pipework. An accumulator or a booster pump resolves it.
Hot water pressure is fine but cold is weak. Why?
That points to a restriction on the cold side specifically, often at the stopcock, a partially closed valve, or scale in the cold pipework. Hot water from a combi or unvented cylinder runs through different pipework, which is why it is unaffected.
Can a combi boiler cause low pressure?
A combi limits flow rate rather than pressure, typically nine to twelve litres a minute. Run two hot outlets at once and each gets less. That is a flow limitation, not a pressure fault, and the fix is a larger combi or a system boiler with an unvented cylinder.
Will a water softener affect my pressure?
A properly installed softener should have minimal impact on pressure. If it is undersized, blocked with sediment or incorrectly installed, it can restrict flow, so if the drop started after one was fitted, have it checked.