Unvented Cylinder Installation Cost

What are you paying for besides the cylinder?

Building Regulations Part G needs an unvented storage system to carry safety devices beyond the thermostat, normally a non-self-resetting energy cut-out and a temperature relief valve or a combined temperature and pressure relief valve. Add the cold inlet group, an expansion vessel, a visible tundish and a discharge pipe to a safe place, and the job is as much a safety installation as a plumbing one.

That is why the cylinder is often the smaller line. Squote, last verified on 17 May 2026, gives a typical UK market range of £180 to £320 for the unvented safety kit supplied, covering a temperature and pressure relief valve, expansion vessel, balanced cold supply and tundish. For a retrofit where the cylinder has no internal vessel, it gives £80 to £180 for an external 18 to 24 litre vessel, also a typical UK market range.

Typical UK market ranges, side by side

BookaBuilderUK, in a 2026 guide with no publication date, gives a typical UK market range of £1,800 to £3,500 for a standard unvented installation including the cylinder, and £3,500 to £5,000 and above for a high-specification unit. It splits that into £700 to £1,800 for materials, £600 to £1,500 for labour, £150 to £400 for disposal and £300 to £800 for optional upgrades.

BestBuilders, updated on 22 August 2026, gives a typical UK market range of £900 to £3,000 fitted, with the cylinder alone at £450 to £2,000, and £1,300 to £3,000 for converting a vented system. It says London and the South East typically add 15 to 25 percent.

Squote gives a typical UK market range for a plumber day rate of £240 to £360 outside London and £300 to £440 in London, with a further £40 to £80 a day for an installer competent in unvented work. An electrician for the isolator and wiring is £280 to £380 outside London and £350 to £480 in London.

What should an unvented quote itemise?

Ask for the quote in lines. If the numbers are lumped together you cannot tell what has been left out, and the cheaper total often turns out to omit the discharge pipework, the electrics or the paperwork.

• The cylinder: make, model, litres, direct or indirect
• The cold inlet group, with its pressure setting
• The expansion vessel, with charge pressure matched to the inlet group
• The relief valve, tundish and discharge pipework to a stated termination point
• Electrical work: isolator, immersion wiring, cut-outs and motorised valve if indirect
• Draining, removal and disposal of the old cylinder or tank
• Making good
• Who notifies Building Control, and what record you receive at handover
• What is provisional, and how it is charged if the work turns out bigger

What pushes the cost of an unvented job up?

Converting from vented. The loft tank, vent pipe and gravity feed come out, and mains-pressure pipework, a discharge route and often electrical work go in. BestBuilders gives the typical UK market range of £1,300 to £3,000 above for the conversion.

The mains supply. Manufacturers set minimums, and one Heatrae Sadia guide for its Megaflo Eco Plus range asks for at least 1.5 bar working pressure and 50 litres a minute. BookaBuilderUK warns that supply upgrades can add a typical UK market range of £500 to £2,000, which is why a competent installer measures the supply before choosing a cylinder.

The discharge route. Part G sets how the tundish and discharge pipe must be arranged, and the figures are in Approved Document G and the manufacturer instructions. A cupboard with no safe place to discharge can mean a long pipe run or a new gully.

Older properties. Squote advises provisional sums for older properties and gives a typical UK market range of £180 to £350 for a Building Control inspection where the installer cannot self-certify.

Does an unvented cylinder need Building Regulations notification?

Yes. Installation is notifiable work under Part G. Either the installer works through a competent person route that self-certifies the job, or Building Control must be told before work starts. What to expect from any competent installer is a compliance certificate or notification evidence plus a commissioning record at handover, which you should keep for a future sale.

A very low quote should prompt a question about notification and the discharge route. The rules are in unvented cylinder regulations under Part G, and unvented cylinder installation describes what is checked on site before any figure is given.

What London Cylinder Specialist charges

A new cylinder installation from London Cylinder Specialist is a fixed £2,400. It covers pipework, installation, commissioning and Building Regulations. The cylinder is not in that figure: it is priced separately from a list by type, size and your preference, and LCS recommends the right one for the home. No VAT is charged.

Cylinder price depends on type, size and your preference; we recommend the right one.

Cylinder troubleshooting and diagnosis, if you are still deciding what the existing system needs, is a fixed £180. There is no call-out fee.

How strong are these figures?

Modest. They rest on three commercial pages, one undated and one a knowledge base that does not name its data. Other cost pages and local listings could not be retrieved when this guide was prepared, so there is no independent check. The spread between guides is itself the useful finding: a like-for-like unvented swap, a conversion with new pipework and a high-specification unit are three different jobs, and a single national average hides that. For a swap without conversion, see hot water cylinder replacement cost.