If several outlets are weak, think beyond one tap
Low flow throughout a property is different from one poor tap. Start by comparing kitchen cold water, upstairs cold water and hot water. If every outlet has changed at the same time, look for something common to the incoming supply. A stop tap may be partly closed, a service valve may have been disturbed, or work in the street may have altered the mains temporarily. If the problem has developed gradually, old pipework, internal corrosion or a pressure-control device may be restricting the system.
Check whether the change is permanent or intermittent
Water pressure can feel worse at busy times if the local main is under heavy demand. A problem that is only noticeable early in the morning or evening may not have the same cause as one that persists all day. Ask a neighbour whether their supply has changed, especially if the issue began suddenly. Your water company may also report work or bursts in the area. If neighbouring properties are normal, attention moves back towards the stop tap, meter, pressure-reducing valve and pipework serving your home.
Flow and pressure are not exactly the same
A house can have reasonable static pressure but poor flow because the pipework cannot deliver enough water when outlets open. Narrow old pipes, a partially closed valve or a restriction at the meter can produce that effect. Conversely, a pressure gauge can show low pressure even before any tap is opened. This distinction is useful because fitting a pump to a restricted supply does not cure the restriction. A plumber may measure both static and working pressure to see how the system behaves under demand.
Hot and cold results can point in different directions
If cold mains outlets are strong but hot water is weak everywhere, the incoming main may be fine and the issue could be within the hot-water system. Combination boilers, unvented cylinders and older gravity-fed arrangements behave differently, so the diagnosis depends on what is installed. If both hot and cold are poor, look further upstream. A sudden loss of pressure after plumbing work can also mean a valve was not reopened fully or debris has moved into a filter or control device.
What a plumber can test
A plumber can check the internal stop tap, measure pressure, compare flow before and after control valves and look for obvious restrictions. If the property has a pressure-reducing valve, filter or water softener, these may need checking as part of the path. Older steel or lead service pipes can also restrict flow, although replacing them is a larger decision and may involve the boundary between private and water-company pipework. Testing avoids spending money on the wrong solution.
Useful details for a quotation or visit
Explain whether the problem affects every tap, when it began and whether it varies during the day. Say what type of hot-water system you have if you know. Mention recent meter work, plumbing alterations or roadworks. A plumber may need access to the internal stop tap and any incoming controls, so note where they are located. If the problem appears to be on the water-company side, it may be better to speak to the supplier first rather than pay for an internal investigation that cannot alter the mains.
Be wary of quick fixes for whole-house pressure
If somebody suggests a pump before measuring the existing supply, ask what problem the pump is intended to solve. Some incoming mains arrangements cannot simply be boosted, and a restriction in the service pipe should be found rather than worked around. The most useful first visit usually establishes the static pressure, the flow available with a tap running and any difference before and after internal valves or filters. Keep a note of those figures if measurements are taken. They make later conversations with the water company or another contractor much clearer. If the problem lies outside your property boundary, paying for internal alterations may achieve nothing. A measured diagnosis is especially worthwhile before considering expensive changes to pipework or stored-water equipment.
This page is general guidance about low water pressure whole house; the cause in an individual home still needs to be established from the actual installation.