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Pressure

Low water pressure in London

Low pressure is a symptom, not a fault, and it has half a dozen possible causes that look identical from the tap. A valve somewhere that is not fully open. Scale narrowing the inside of old pipework. A pressure-reducing valve that has quietly drifted out of adjustment. Or a system that was never going to deliver a strong shower without help. The way to tell them apart is to test, which is cheaper than working through the parts one at a time.

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What we cover

What this includes

  • Whole-house and single-fixture pressure problems
  • Pressure and flow measured at the incoming supply
  • Pressure-reducing valves checked and adjusted
  • Limescale-furred pipework, aerators and shower heads
  • Part-closed and seized stopcocks and valves
  • Pumps and accumulators where they are genuinely the answer
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Before you call

Worth knowing first

A little of this might mean you do not need to call us at all — we would still rather you knew it.

Whole house, or just one tap?

This is the first question, and you can answer it before anyone visits. Run every cold tap in turn. If one fixture is weak and the rest are fine, the problem is local to it — a scaled aerator or shower head, a seized isolation valve underneath, a kinked flexible tail, a worn cartridge. If everything in the house is weak, the problem is on the incoming supply or the system as a whole, and that is a completely different set of checks.

Pressure and flow are not the same thing

Pressure is how hard the water pushes. Flow is how much of it actually arrives per minute. A house can have perfectly respectable pressure at the boundary and still deliver a disappointing shower, because the water is being squeezed through pipework that limescale has narrowed over the decades, or through a supply pipe that was sized for a Victorian household rather than a power shower and a washing machine running at once. Measuring both is what separates the two, and London’s hard water makes the second one common here.

Valves drift, and stopcocks seize

Two of the most common causes are also the least dramatic. A pressure-reducing valve set correctly years ago can drift out of spec as it ages. A stopcock left three-quarters closed after somebody else’s work throttles the whole house, and nobody thinks to look at it. Ninja Plumbers tests the supply before touching anything, because it is the only way to tell an adjustment from a replacement — and swapping parts speculatively is how people end up paying for a new valve that was never the problem.

What system you have decides what can be done

If your hot water comes from a combi boiler, everything in the house runs off the mains and the answer lies in the supply, the pipework or a valve — the mains cannot be pumped. If you have a cold tank in the loft and a hot cylinder in a cupboard, the system is gravity-fed, the pressure comes from how high the tank sits, and a correctly matched pump is often the right fix. That is covered in detail on our shower pumps page.

Pricing

What affects the price

Low pressure is priced in two stages: finding the cause, then fixing it. Finding it is a fairly set piece of testing. The fix can be a quick valve adjustment or a much bigger job, and you see that price before deciding.

How far the testing has to go

A weak kitchen tap may be solved at the tap itself. When every outlet in the house is weak, the engineer has to measure pressure and flow at the stopcock and at points around the house, and that fuller investigation takes longer.

The stopcock in the pavement

Replacing an indoor stopcock or pressure-reducing valve means turning the supply off outside first. If the outside stopcock is buried, seized or shared with next door, freeing it or getting Thames Water to attend can add time and sometimes a second visit.

Scale inside old pipework

Scale in a shower head or aerator is cleared in minutes. Scale that has narrowed the inside of old copper or galvanised pipe cannot be cleaned out in place, so the worst lengths have to be replaced, which is a bigger job.

Whether boosting is the answer

When nothing is actually faulty and the water simply arrives with too little push, a pump on a tank-fed system, or a storage accumulator where the mains is weak, may be the fix. Both mean equipment, somewhere to house it and usually a power supply.

The price is agreed before any work starts. We take card and cash.

Questions

Common questions

Only my shower is weak. Everything else is fine.

Then it is almost certainly local to that shower. A scaled shower head, a part-closed isolation valve, a worn mixer cartridge or a crushed flexible hose account for most of these, and all of them are small jobs.

Is low pressure the water company’s problem or mine?

It can be either. Testing at the incoming supply, before and after your stopcock, shows whether the water is arriving weak or being lost inside the property. If the whole street is affected it is one for the water company, and we will say so rather than charge you to find that out twice.

Will a pump fix it?

Only on a gravity-fed system with a tank in the loft. If your water comes from a combi or a mains-pressure unvented cylinder, pumping the mains supply is not permitted, and anyone offering to do it is selling you the wrong thing.

My pressure dropped suddenly. What changed?

A sudden drop usually means something specific: a valve left part-closed after other work, a failed pressure-reducing valve, a leak on the supply pipe, or a problem out in the street. Sudden is useful information, so mention it when you call.

Why is my pressure worse in the mornings and evenings?

Usually because everyone else is using water at the same time. At peak hours demand on the street’s mains rises and pressure at your tap can drop. In a converted house where several flats share one supply pipe, the effect is sharper, because a shower running upstairs takes from the same pipe as yours. Testing at a busy time and a quiet time shows whether that is what is happening.

Will switching to a combi boiler improve my pressure?

Only if the mains coming into the house is strong. A combi runs everything straight off the mains, so on a good supply it can feel like a big improvement over an old tank-fed system. On a weak or shared supply it can make things worse, because the hot water now competes with every cold tap. Having the incoming flow measured before choosing a combi avoids an expensive disappointment.

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Need low water pressure in London?

Describe the problem and give us your area, and we’ll tell you the price before anyone starts work.

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