Hot Water Cylinder Replacement Cost London (2026 Guide)

How much does it cost to replace a hot water cylinder?

Three public guides give different answers, because each prices a different job. The table sets them side by side. It is the only comparison of its kind on this site; the other cost guides link here instead of repeating it. For the fixed LCS prices, see the pricing page and the cylinder cost hub.

Why do the figures differ so much?

They are not pricing the same job. A vented swap on a gravity system reuses the loft tank, the vent and most of the pipework. An unvented swap adds a cold inlet group, an expansion vessel, a relief valve and a tundish, and it is notifiable work under Part G of the Building Regulations. A guide that folds those parts into its unvented figure reads higher than one that prices the cylinder and a day of labour.

Region is the second gap. BestBuilders 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.

The third gap is who wrote the page. BestBuilders, BookaBuilderUK and Squote are commercial sites, not independent price surveys. That does not make the figures wrong, but it is a reason to read them as ranges and not quotes.

How much does changing the type of cylinder add?

Changing the arrangement is the largest swing. BestBuilders gives its typical UK market range of £1,300 to £3,000 for a vented to unvented conversion because the job adds a discharge route, mains-pressure pipework and often electrical changes. A swap that keeps the type, size and position stays towards the lower end.

Specification matters inside a type. Squote lists a heat-pump compatible 210 litre cylinder at a typical UK market range of £950 to £1,800 supplied, well above a standard 210 litre unit. If you are weighing the unvented route, unvented cylinder installation cost covers the extra items line by line, and converting a vented system to unvented covers what else changes.

What do cylinder replacement quotes leave out?

Access and making good. BookaBuilderUK gives a typical UK market range of £150 to £600 for making good ceilings or flooring, and notes that tight hatches and corroded pipework add labour. Disposal of a large old cylinder is its own line in some guides.

Findings on the day. Corroded pipework, a seized stopcock or a worn valve group may need replacing while the cylinder is out. A good quote lists these as provisional items and says how they are charged. A quote that does not is hiding a risk in the total.

Building Control. Squote lists an inspection at a typical UK market range of £180 to £350 where the installer cannot self-certify an unvented job, so it is fair to ask any installer who notifies the work.

Ask every quote to separate the cylinder from labour, valve kit, electrics, disposal and making good. A single lump sum hides which parts are cheap and which are padded. What sits inside the labour line is covered in what replacement labour covers, and the full list of lines is in the cylinder replacement quote checklist.

What London Cylinder Specialist charges

A cylinder replacement from London Cylinder Specialist is a fixed £1,450 for labour and miscellaneous parts. The cylinder is priced separately: it is chosen from a price list by type, size and your preference, and LCS recommends the right one for the home. No VAT is charged.

If the fault is not yet certain, cylinder troubleshooting and diagnosis is a fixed £180. There is no call-out fee. A leak from a union or an immersion boss is a far smaller job than a failed shell, and repair or replace a hot water cylinder gives the decision rule. The straight swap is described under like-for-like cylinder replacement.

How solid is this evidence?

Thinner than it looks. Every figure above comes from three commercial pages, one of them undated, and the ranges overlap only loosely. Other cost pages could not be retrieved when this page was prepared, and no manufacturer price list was available, so there is no independent check on the numbers. Treat the spread as the finding, and review the figures when a guide is updated.

Sources: BestBuilders cylinder replacement cost guide (updated August 2026); BookaBuilderUK unvented cylinder cost guide (2026, undated); Squote cylinder pricing knowledge base (verified May 2026); Approved Document G, hot water safety and unvented systems.