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Planned work · London · from £1,450 fitted

Unvented Hot Water Cylinder Installation in London

Mains-pressure hot water at every tap, no loft tank, showers that feel like showers.

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Unvented cylinder installation in London
No call-out feeNo night or weekend surchargeFixed price before we start12-month workmanship guarantee

Unvented cylinders are the upgrade older London homes feel most, installed by G3-qualified engineers, because the law and physics both insist.

What you get

Unvented cylinder installation in London: what the price includes

  • 01
    G3 qualified installation

    Unvented work legally requires the G3 ticket, ours carry it, and the Building Regs notification is included.

  • 02
    Sized for the household

    Bathrooms, occupants and mains flow measured; an undersized cylinder runs cold, an oversized one runs bills.

  • 03
    Safety stack done right

    Tundish, discharge pipework and expansion controls installed to spec, the parts that make “unvented” safe.

  • 04
    Annual service available

    The expansion vessel and safety valves want a yearly check, pairs with the boiler service visit.

  • 05
    G3 registered, and the paperwork filed

    Unvented cylinder work is notifiable under Part G of the Building Regulations and requires a specific G3 qualification on top of Gas Safe registration. We hold it, and we notify building control, which matters when you sell the house and the buyer's solicitor asks.

What this means in London

Local conditions we work around

Unvented cylinders and hard water are a demanding combination. At London hardness the coil scales, heat transfer falls away, and performance degrades long before anything actually fails, which is why the annual service genuinely matters here rather than being a formality, and why a scale reducer on the mains is worth its cost. The G3 requirement applies regardless: unvented work is notifiable and must be done by a qualified operative, with the discharge arrangement properly terminated.

Where we do this in London

Covered across London

Same published rate card and the same twelve-month workmanship guarantee everywhere below, there is no postcode loading. Each area has its own page with an arrival time taken from our job records rather than chosen for a website.

EnfieldWembleyHarrowStratfordWalthamstowTottenhamWatfordSt AlbansHemel HempsteadBorehamwoodPotters BarHertford All London areas →
Straight answers

Unvented cylinder installation in London, your questions

Unvented vs a combi?
Two showers running at once is the deciding question. Combis serve one outlet well; a cylinder serves the whole house simultaneously. Big household, more than one bathroom, cylinder wins.
What does it cost?
From £1,450 fitted replacing an existing cylinder; full conversions from vented (removing tanks, upgrading pipework) £2,500–£4,000. Fixed after survey.
Why does mine dribble from an outside pipe?
The discharge pipe running means a safety valve is passing, commonly the expansion vessel has lost its charge. It's the system telling you it needs its annual service; ignore it and the next part to fail is pricier.
How is it different from a normal hot water tank?
It is sealed and fed at mains pressure, so every hot tap and shower runs at the same pressure as the cold. No loft tank, no pump needed, and a far better shower. It also has safety devices that a vented tank does not, which is why the annual service is not optional.
Does it need servicing every year?
Yes. The expansion vessel, the temperature and pressure relief valve and the tundish all have to be checked annually. In hard-water London the discharge components scale up faster, and a seized T and P valve on a mains-pressure cylinder is genuinely dangerous.
Will my mains cope with it?
That is the first thing we measure. An unvented cylinder needs adequate incoming flow rate and pressure, and if your supply cannot deliver it the system will disappoint however good the cylinder is. We test at the stopcock before quoting.
How does London hard water affect heating work?
Considerably. Scale builds on the hottest surface in the system, which is the boiler heat exchanger, and every millimetre costs efficiency and life. It is why we flush before commissioning a new boiler here, why kettling is the most common noise complaint we get in London, and why an unvented cylinder in this city genuinely needs its annual service rather than nominally needing it.
24 hours · 365 days · London

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