Low Water Pressure and Weak Showers in London
Most weak showers in London come from the system inside the property, not the water company. We measure the pressure and the flow, then tell you which fix will change it and which will not.
Book a Plumber Call 020 3764 2713✓Pressure and flow both measured✓£150 inc VAT call out✓WaterSafe approved✓London, inside the M25
Both numbers measuredPressure and flow, not just a gauge reading
£150 inc VATStandard call out covers the full survey
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London onlyEvery job inside the M25
PRESSURE VERSUS FLOW
Two numbers decide your shower
Most pressure fixes disappoint because only one of them was measured.
Pressure
The force pushing the water, measured in bar. It decides how hard the water arrives.
Flow
How much water actually arrives, measured in litres per minute. It decides whether two taps can run at once.
Why it matters
A flat can read 4 bar standing pressure and still deliver a miserable shower, because the pipe feeding it is too narrow to carry the volume once a tap opens. If someone quoted you for a pump without measuring the flow rate, they guessed.
GRAVITY SYSTEMS
Why upstairs is always worse
If you have a cold water tank in the loft, your pressure comes from gravity alone. Nothing is faulty, that is simply what gravity gives you.
The maths
Ten metres of height gives you roughly 1 bar, so every metre you go up costs you 0.1 bar.
An upstairs shower two metres below the tank gets about 0.2 bar. A ground floor tap five metres below the same tank gets more than double. A gravity system rarely exceeds 1 bar anywhere in the house.
What each outlet needs
- Wash basin: 6 l/min
- Water saving shower: 9 l/min
- Kitchen sink: 10 l/min
- Standard shower: 14 l/min
- Bath: 18 l/min
- Power shower: 22 l/min
Someone showering at 14 while the kitchen tap runs at 10 needs 24 litres a minute arriving at the property.
What your pipes can carry
- 15mm copper, 20mm MDPE: 20 l/min
- 22mm copper, 25mm MDPE: 40 l/min
- 28mm copper, 32mm MDPE: 80 l/min
- 35mm copper: 120 l/min
A 15mm incoming main caps you at 20 litres a minute whatever the street pressure is. Plenty of older London properties are still on 15mm, or on lead.
THE SURVEY
How we test your supply
The survey takes under an hour and it is the only way to know which fix is the right one.
The survey is carried out under our standard call out fee of £150 including VAT. That covers the visit, the static and dynamic pressure readings, the flow rate measurement and our recommendation. See our rates.
Static pressure
A gauge on an outside or kitchen tap with nothing else running. Average across the UK is 2 to 3 bar. Your water company is only obliged to deliver 1 bar and 9 litres a minute at the boundary, well below what a modern bathroom wants.
Dynamic pressure and flow
The numbers that decide the job. We measure with water running, then open a second and third outlet and watch what happens. A supply that holds up on one tap and collapses on two has a flow problem, and no pump on the hot side will fix that.
What you get
Three figures and a straight recommendation, including when the honest answer is to leave the system alone. We quote from the readings rather than from a guess.
YOUR OPTIONS
The four fixes
Which one applies depends entirely on what the survey finds.
Convert to an unvented cylinder
The biggest change available, and the right answer for most houses with a decent mains supply. Takes you from 0.2 to 0.5 bar up to 2 to 4 bar at every outlet, and frees up the loft.
A 22mm outlet delivers around 57 l/min of mixed hot water, a 28mm outlet around 115. A 24kW combi manages 9.5 and even a 43kW combi only reaches 17.8.
Needs 1.5 bar dynamic, 20 l/min, 22mm incoming. Unvented cylinders →
Fit a cold water accumulator
For reasonable pressure but poor flow. A sealed vessel stores mains water under pressure and releases it when you open a tap, giving the supply a buffer.
Delivers in excess of 80 l/min, uses no electricity, has no moving parts and keeps working in a power cut. Usable volume is about half the vessel, so 130 litres gives roughly 65 litres of boosted water.
Needs somewhere to put it. They are not small.
Add a charger pump
For an incoming main below 2 bar, too low for an accumulator to charge on its own. The pump sits upstream and lifts pressure to as much as 3.5 bar.
Runs at around 38 dBA, quiet enough not to wake the house, and only a portion of the water passes through it. The accumulator keeps working if the pump is off.
Also useful where the main is fine at ground level but the accumulator sits several floors up.
Upgrade the incoming main
If your supply pipe is 15mm or lead, replacing it with 25mm MDPE raises your flow ceiling from 20 l/min to 40. On its own this is sometimes the whole fix.
A bigger pipe improves flow and dynamic pressure. It does not raise static pressure, which is set by the water company and your position relative to the main.
HONEST ADVICE
SHOWER PUMPS
What about a shower pump?
A shower pump is a reasonable fix on a gravity system when the budget will not stretch further, and we do fit them. You should know what you are buying.
Pumps are noisy. You hear them every time anyone opens a tap. They have moving parts under constant load, so they fail, usually after a few years of heavy use, and then you are back where you started.
They also only boost what the tank can supply, so they help with pressure and do nothing for a genuine flow shortage. Weighed against converting to unvented, the conversion costs more up front and removes the problem rather than masking it.
When a pump is the right call
- Loft tank and pipework are sound
- You want a better shower for less money
- Only one or two outlets need help
- Mains supply is too weak for unvented
When it will disappoint
- The real problem is flow, not pressure
- You want every outlet improved
- Pump noise would carry into bedrooms
WHEN TO WALK AWAY
When an unvented cylinder is the wrong answer
We would rather say this before you spend money than after.
Your mains cannot support it. Below 1.5 bar dynamic or under 20 litres a minute, an unvented cylinder will underperform the system you already have. If an accumulator or a pumped break tank cannot bridge the gap, keep a stored system.
Your pipework will not take it. In properties over thirty years old, putting 3 to 4 bar through fragile or inaccessible joints invites leaks in places you cannot get at. Sometimes the right answer is a vented replacement, or a repipe first.
You need the cheapest working option. A like for like vented replacement is a fraction of the cost of a full unvented conversion. If the budget is the constraint, that is a legitimate choice and we will quote it without a lecture.
We will tell you if
- Your supply will not carry an unvented cylinder
- A cheaper fix solves the actual complaint
- The honest answer is to leave it alone
HOW IT WORKS
From first call to fixed
1
Tell us what is happening
Call, book online or send photos through the contact form. Tell us which outlets are weak and whether you have a tank in the loft.
2
We measure the supply
Static pressure, dynamic pressure and flow rate, then we open more outlets to see where it falls over. Under an hour, under the standard call out fee.
3
You get the numbers and a recommendation
Three figures, what they mean, and which of the four fixes applies. Including when the answer is that nothing needs doing.
4
We quote and carry out the work
Priced from the readings. G3 qualified for unvented work, WaterSafe approved for supply pipe work, and we certify our own.
Why is my shower pressure low upstairs but fine downstairs?
You almost certainly have a cold water tank in the loft. Pressure comes from the height between the tank and the outlet, and you lose 0.1 bar for every metre you go up. An upstairs shower sitting two metres below the tank gets around 0.2 bar. A downstairs tap five metres below it gets more than double. Nothing is faulty.
Will a shower pump fix low water pressure?
On a gravity system, it will improve the shower. It will not help if the real problem is flow rate rather than pressure, and it adds noise and a part that eventually fails. We measure both numbers before recommending one.
What water pressure should I have in London?
Average UK standing pressure is 2 to 3 bar. Your water company only has to supply 1 bar and 9 litres a minute at the property boundary. Anything at or above 1.5 bar with 20 litres a minute opens up every option including an unvented cylinder.
Can low water pressure be fixed without replacing the cylinder?
Often, yes. A blocked line strainer on an unvented cylinder, a partly closed isolation valve, a sticking pressure reducing valve or an undersized incoming main are all fixable without touching the cylinder. We check the cheap causes first.
How much flow do I need for two showers at once?
Two standard showers want about 28 litres a minute between them, and two power showers want 44. Very few London mains deliver that unaided, which is where an accumulator or an unvented cylinder with a 28mm outlet comes in.
Do you charge for a pressure and flow survey?
The survey is carried out under our standard call out fee of £150 including VAT. That covers the visit, the static and dynamic pressure readings, the flow rate measurement and our recommendation. See our rates for full details.
Weak shower, or pressure that drops when someone turns a tap on?
Book a pressure and flow survey under our standard £150 inc VAT call out, and we will tell you which fix actually changes it.
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