What a cylinder replacement costs in London

Start with what we do not do

We do not supply or fit hot water cylinders. That is not modesty and it is not a scheduling problem. Installing an unvented cylinder over 15 litres is controlled work under Part G of the Building Regulations. It has to be done by someone holding the unvented hot water qualification, and it has to be either notified to building control or self-certified by an installer registered on a competent person scheme. Handing you a price for work we are not registered to certify would be the first thing wrong with the quote.

So this page has no figure for a cylinder replacement on it. What it has instead is the shape of the bill — the things a real quote is made of, and the ones that quietly double it.

Our own number is the only price here: £150 per hour, agreed before we attend, with no call-out fee and no evening or weekend uplift. That covers the work we actually do around a cylinder, which is the pipework, the leaks and the damage. Not the vessel.

Why the number you are searching for does not exist

Type the question into Google and you will get ranges. Most of them come from sites that have never held a spanner and are selling your details to whoever bids highest. The ranges are wide enough to be safe and vague enough to be useless.

The honest reason there is no single number: "replacing a cylinder" describes at least five different jobs.

• Like for like. A vented copper cylinder swapped for the same thing in the same place. Least work, fewest surprises.
• Like for like, unvented. An existing unvented cylinder replaced with a comparable one. The controls and the discharge route already exist, so they only need checking and reconnecting.
• Vented to unvented conversion. A different job wearing the same name. See below.
• A change of size or position. The new vessel does not land on the old footprint, so the pipework is re-made.
• A replacement forced by damage. There is a wet floor, a stained ceiling below, or a cupboard that has been quietly soaked for months. Now there is a second trade involved.

Two quotes that both say "replace hot water cylinder" can be describing any two of those. That is the whole problem, and it is fixable by asking for the breakdown.

The seven things that move the price

1. The cylinder itself

Capacity, coil arrangement and pressure rating all change the cost of the vessel. A single-coil vented copper cylinder, a twin-coil unvented stainless vessel sized for a solar or heat pump input, and a smart cylinder with its own controls are not interchangeable products at the same money. Ask which model is quoted, by manufacturer and part number, not by description.

2. Getting to it

An airing cupboard on the ground floor with a door wide enough to walk the vessel through is the cheap case. A cylinder in a loft, on a third-floor landing, behind a fitted wardrobe, or in a cupboard that was built around it, is labour before any plumbing starts. Access is the single most common reason two quotes differ by hours rather than minutes, and it is the one you can see for yourself before anyone visits.

3. Whether the pipework has to be altered

If the new cylinder's tappings line up with the existing flow, return, cold feed and draw-off, the connections are remade and that is that. If the vessel is a different height or diameter, or the connections sit on the other side, the pipework gets cut back and re-run. On older London properties there is a third possibility: the existing pipework is in a state where nobody sensible reconnects to it, and the honest quote says so up front rather than discovering it on the day. That re-run is the part we do — see pipework repair and replacement.

4. Vented to unvented, which is a different job

This is the biggest single step change in cost, and it is often presented as a small upgrade. Going unvented means:

• Losing the loft tanks, and capping or removing the old feed and vent pipes.
• Adding the safety and control set: expansion vessel, pressure reducing valve, expansion relief valve, temperature and pressure relief valve.
• Creating a discharge route — a tundish and a discharge pipe that has to run to a safe, visible termination that satisfies Part G. In a flat, or a converted house where the cupboard sits in the middle of the building, finding that route is sometimes the most expensive hour of the whole job.
• Confirming the incoming mains can actually deliver the flow rate the cylinder needs. An unvented cylinder on a weak supply gives you a worse shower than the one you replaced.
• The notification or self-certification that the regulation requires.

Any quote that converts you from vented to unvented and does not mention a discharge route is incomplete. Ask where the pipe terminates, and go and look at where they point.

5. Electrics and controls

An immersion heater needs its own supply, and the existing one may be old enough that an electrician has to be involved. Add a cylinder thermostat, a motorised valve, a wiring centre or a connection to a smart controller and there is a second trade on site. Whether that trade is in the quote or arranged separately by you is worth establishing before the day.

6. Getting the old one out and away

The old cylinder has to be drained, cut out and removed from the building. If it will not go back through the door it came in through, it gets cut up in place. Copper has a scrap value that some installers credit against the bill and some keep; there is no right answer, but there is an answer, and you can ask for it. Removal and disposal should be a named line, not an assumption.

7. Making good

Cupboard floors get cut. Boxing gets removed. If the cylinder was replaced because it had been leaking, there is usually a floor, a ceiling or a section of plaster underneath it that needs attention. Most cylinder quotes do not include any of this, which is correct — it is not plumbing — but it means the plumbing quote is not the cost of the project. That half is repair and reinstatement, and if the damage came from a leak it may sit under your buildings insurance rather than your own pocket. How trace and access works covers what a claim will and will not reach.

What an itemised quote should contain

Ask for these as separate lines. A quote with one number on it cannot be compared with anything.

Line	What you are checking
Cylinder, by make and model	Capacity, coil count, vented or unvented. Two quotes on different vessels are not competing.
Labour, with an estimated duration	Whether it is a day rate, an hourly rate or a fixed price, and what happens if the day runs long.
Controls and safety kit	On an unvented job, the expansion vessel, PRV, expansion relief and T&P valve should appear. On a conversion, so should the tundish and discharge pipe.
Pipework alterations	Priced, or excluded and flagged. "As required" is not a price.
Electrical work	Included, or by others. If by others, whose others.
Removal and disposal of the old cylinder	Included, or left in your hallway.
Building control notification or self-certification	Who does it, and whether you receive the certificate. On unvented work this is not optional.
Making good	Almost always excluded. Confirm it, so you are not surprised by a cut floor.
VAT	Whether the total shown includes it.
Guarantee	Manufacturer warranty on the vessel and workmanship warranty on the install are two different things with two different lengths.

Run both quotes through that list and the cheaper one often turns out to be the one that excluded three lines. That is not dishonesty; it is usually just a quote written quickly. It is still your money.

Where we actually come into this

People arrive at a cylinder replacement by two routes. One is age and a planned upgrade, and for that you want an installer with the unvented registration, not us.

The other is water: a damp cupboard floor, a stain spreading on the ceiling below, pressure that will not hold, or a tundish that has started to drip. That is our work. We find where the water is coming from, and often it is not the cylinder — it is a compression joint above it, an immersion boss seal, a valve that is passing and discharging exactly as it was designed to, or a pipe under the floor that happens to run past the cupboard. Replacing a sound cylinder because something near it was wet is an expensive way to not fix a leak.

If we do find the cylinder itself has failed, we will say so plainly and tell you to get it replaced by someone qualified to do it. We will do the pipework and the damage. We will not quote you for a vessel we cannot certify. More on how the hot water side fails is in the hot water and cylinders guide.