Hot water cylinder replacement cost: what drives it
You will not find a made-up price on this page, because every cylinder job is different. What I can do is explain the things that genuinely decide what replacing a hot water cylinder costs, so you can compare quotes properly.
Gas Safe registered 25 years in the trade 12 years running the business
Written by Chris Gill, C Gill & Son Plumbing & Heating ·
Vented or unvented: the biggest factor
A vented cylinder — the traditional copper tank fed from a header tank in the loft — is the simpler and cheaper appliance to replace like for like. An unvented cylinder costs more as a product and must be fitted by a qualified installer with the right certification, notified to building control, and given a safe discharge pipe run to a suitable drain.
Switching from vented to unvented is a bigger job again: the loft tank and its pipework come out, the mains supply has to be checked for pressure and flow, and the safety controls are added. Our vented vs unvented cylinder guide explains the difference in daily use.
Size and type of cylinder
Cylinders are sized in litres, and the right size depends on your bathrooms and how your household uses hot water. A larger cylinder costs more and takes longer to fit, but undersizing to save money means running out of hot water — a false economy.
There are also different grades: standard cylinders, and high-recovery or stainless steel models that heat faster and last longer. The label on your existing cylinder tells an engineer a lot, so a photo of it is useful when you ask for a quote.
Position and access
A cylinder in an easy airing cupboard with the pipework in the right place is the straightforward case. Costs rise when the cylinder is in a tight loft, under eaves, or boxed in behind tiling that has to come apart and be made good. Solid floors, long pipe runs and awkward drain points for the discharge pipe all add time.
Weight matters too: a full cylinder is extremely heavy, so the new one needs a sound, level base, and the old one has to be drained and got out of the house.
What else might be needed
New controls: a cylinder thermostat and motorised valve if yours are old
An expansion vessel or new relief valves on unvented systems
Pipework alterations if the new cylinder's connections differ from the old one's
Making good: shelves, boxing-in or decoration disturbed during the swap
Servicing and running costs
An unvented cylinder should have its safety valves and expansion vessel checked every year, often done at the same visit as the boiler service. That ongoing check is part of owning an unvented system and worth factoring in when you choose between vented and unvented.
Getting a real figure
The honest way to price a cylinder replacement is to look at your setup. Send photos of the cylinder, its label, the pipework around it and the loft tank if you have one, via WhatsApp or the quote form. Our hot water cylinder installation page explains the work itself, and Chris will give you a fixed, no-obligation quote after a look.
Covering Neath, Port Talbot, Swansea and the surrounding area.
Common questions
Hot water cylinder replacement cost FAQs
Clear answers before you arrange a visit.
How much do hot water cylinders cost?+
It depends on the type, size and grade of cylinder and the work to fit it. A like-for-like vented swap is the simplest case; unvented cylinders cost more and must be fitted by a qualified installer. A survey gives you a fixed figure.
How much does an unvented cylinder cost?+
More than a vented one, both as a product and to install, because of the safety controls, the discharge pipework and the certification required. The exact figure depends on size, position and your mains supply.
Is it worth switching from vented to unvented?+
If your mains pressure and flow are good and you want strong showers at more than one outlet, often yes. If the mains is marginal, a vented system may serve you better. The survey answers this for your house.
Can I replace just the cylinder and keep my boiler?+
Usually, yes. The boiler and cylinder are separate appliances. If both are old, planning them together can save disturbance, but there is no rule that says they must be changed at the same time.
