Low water pressure is one of the most common calls we get across Essex and London, and the cause is often simpler than people expect. Sometimes it is a stiff stopcock or a scaled-up shower head; sometimes it is the mains supply, the boiler or an old lead pipe under the front garden. This guide walks through the likely causes in the order we would check them, so you can rule out the easy things before paying for a visit.
Pressure is the force pushing water through the pipe, measured in bar. Flow is how much water actually comes out, measured in litres per minute. A house can have decent pressure but poor flow if the pipework is narrow or partly blocked, and that distinction changes what needs fixing. Most water companies in our area, including Essex & Suffolk Water, Affinity Water and Thames Water, are only obliged to deliver around 1 bar at the boundary stopcock. That is enough to fill a 4.5 litre jug in roughly 30 seconds from a kitchen cold tap.
Before you look inside, ask the neighbours. If their pressure has dropped at the same time, it is almost certainly a mains issue such as a burst, planned works or peak demand on a warm evening. Check your supplier's live incident map, and call them if nothing is listed. If it is only your house, the fault is on your side of the boundary and the checklist below applies.
A surprising number of low pressure jobs end with us turning a valve a few times. The internal stopcock, usually under the kitchen sink or in a downstairs cupboard, gets nudged shut during other work or is left half closed after a leak. Turn it fully anticlockwise, then back a quarter turn so it does not seize open. Old brass stopcocks in Victorian and 1930s houses across east London and south Essex often have a worn washer or a jumper that has dropped, which throttles the supply even when the head is wide open.
There is a second stopcock at the boundary, usually under a small metal or plastic cover in the pavement or front path. It belongs to the water company, but it can be partly closed after a meter fitting or a repair. If your internal stopcock is fine and the whole house is weak on cold, ask the supplier to check the boundary valve before you spend money on anything else.
If cold pressure is fine at the kitchen tap but drops off elsewhere, the fault is inside the house. Hard water is the main culprit across Essex and London. Limescale builds up inside copper pipes, tap cartridges, shower heads and isolation valves, and a half-inch pipe can lose a third of its bore over twenty years. Cleaning the shower head and tap aerators in white vinegar overnight fixes more complaints than you would think. Small quarter-turn isolation valves under basins also fail internally and quietly choke one outlet.
Whole-house weakness on cold with a healthy boundary supply usually points to the supply pipe itself. Many pre-1970 houses still have a lead or galvanised iron pipe from the street, often only 15mm or smaller and heavily furred inside. Replacing it with 25mm or 32mm MDPE plastic typically transforms pressure and flow. In our experience a straightforward run under a front garden falls somewhere between £900 and £2,500 depending on length, surface and whether the water company needs to connect at the boundary. Some suppliers offer a free connection or contribution when you replace lead, so ask before booking.
If cold is strong but hot is weak, look at how the hot water is made. Combi boilers heat water on demand through a plate heat exchanger, and in hard water areas that exchanger scales up over five to ten years. The signs are hot water that slows to a trickle while the cold runs freely, and often a boiler that cycles or shows a fault code. A power flush or a new plate exchanger normally sorts it, and fitting a scale reducer on the cold feed slows it happening again.
On a gravity system, with a cold tank in the loft feeding a copper cylinder, hot pressure depends entirely on the height of that tank. Upstairs showers on these systems are often barely usable. A shower pump, a pressurised unvented cylinder or a combi conversion are the usual fixes, in rising order of cost. Unvented cylinders and pumps also have their own failure points, so a sudden drop on an existing setup is often a tired pump, a blocked strainer or a sticking pressure reducing valve rather than the cylinder itself.
Do the jug test, check both stopcocks, clean the aerators and ring your supplier if the neighbours are affected. If you have done that and the problem remains, or you find a damp patch or hear running water when everything is off, stop there. A hidden leak on the supply pipe will drop your pressure and can undermine a floor or path, and it will show on a meter reading even with all taps closed. We can pressure test the supply, trace leaks and confirm whether the fault is pipework, appliance or valve before recommending anything, and a diagnostic visit is a fraction of the cost of guessing at a new boiler.
UK water companies must supply at least 1 bar at the boundary, though many homes in Essex and London see 2 to 4 bar. Anything much below 1 bar, or under about 8 litres per minute at the kitchen cold tap, is worth investigating.
Not directly. UK water regulations do not allow pumping straight from the mains above 12 litres per minute, so a booster set needs a break tank. Pumps are fine on gravity hot and cold systems fed from a loft tank.
Meters and their fittings narrow the supply slightly, and a boundary stopcock is sometimes left partly closed after the work. Ask your supplier to check the valve first, as this is their responsibility and free to fix.
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