Unvented CylinderInstallation
Mains-pressure hot water, supplied and fitted from £1,640 + VAT (£1,968 inc VAT). Guide price in 30 seconds, fixed price after a free survey.
Cylinder job facts
What will my cylinder cost?
Four quick choices and you have a guide price built from the figures we actually charge. No email address needed.
Your guide price
£1,702 to £1,998 + VAT
£2,042 to £2,398 inc VAT
Usually 1 day on site. Hot water is off for most of that day.
What that covers
- 210 L unvented cylinder, fittings and sundries£1,150
- Labour: replace an existing unvented cylinder (1 day)£700
- • G3-qualified installer, Building Regulations notification included
- • Old cylinder removed and disposed of
- • Tested, commissioned and shown to you before we leave
- • 12-month guarantee on workmanship, manufacturer warranty on the cylinder
150 L unvented cylinder supplied and fitted in Great Bedwyn, Sep 2025: £1,981 inc VAT all in.
This is a guide, not a quote. We survey for free and give you one written fixed price before any work starts.
Book a free survey for this priceOr call 01264 502027Three ways we do cylinders
Like-for-like unvented replacement
From £1,640 + VAT
£1,968 inc VAT
Your existing unvented cylinder has failed or is past its best. Same position, one day, hot water back by evening.
Book a free surveyVented to unvented conversion
From £2,600 + VAT
£3,120 inc VAT
Lose the loft tank and get mains-pressure hot water to every tap and shower. Two days on site.
Book a free surveyCylinder for a heat pump
Priced on survey
Larger coil, sized for lower flow temperatures. Priced on survey with your heat pump installer.
Heat pump cylindersSigns your cylinder is on its way out
- Hot water runs out faster than it used to, or takes longer to reheat
- Water dripping from the discharge pipe outside, or the tundish, more than a few drops
- Rusty or discoloured hot water, or a metallic smell
- Banging or gurgling from the cylinder cupboard
- It is more than 15 years old and has never had the expansion vessel or valves serviced
- Damp patch or corrosion around the base of the cylinder
Vented or unvented?
| Vented (tank in loft) | Unvented (mains pressure) | |
|---|---|---|
| Shower pressure | Depends on loft height, often weak | Strong, same at every tap |
| Loft tank | Needed | Gone |
| Needs a pump for showers | Usually | No |
| Installer | Any plumber | G3 qualified, notified to Building Control |
| Depends on mains flow | No | Yes, we test it first |
| Annual check | Not usually | Recommended (valves and expansion vessel) |
Unvented cylinders by Will Gaze
Cylinders are the job I enjoy most: a day's careful work that transforms how a house feels every morning. 22 years in the trade, G3 qualified for unvented hot water, G1 trained for heat pump cylinders, WaterSafe approved. I do the survey, I do the fitting, and I hand it over to you working.
- G3 unvented hot water qualification, Building Regulations notification included
- WaterSafe (WRAS) approved plumber
- Mains flow and pressure tested before we recommend a cylinder
- Old cylinder removed and disposed of, cupboard left clean
- We do not work on gas or oil boilers and will say so if that is what you need
Cylinder installationacross Andover, Marlborough & Hungerford
Andover (SP10, SP11), Marlborough (SN8), Hungerford (RG17), Pewsey (SN9), Tidworth (SP9), Stockbridge (SO20) and the villages between, from our base near Marlborough.
Read before you decide
The true cost of upgrading to an unvented cylinder
What changes in the house, what it costs, and the questions to ask before you commit.
Read the guide →Hot water cylinder guide
Vented, unvented, direct, indirect: which is which and which suits your home.
Read the guide →Cylinder replacement cost guide 2026
Where the money goes in a cylinder swap and how to keep the bill sensible.
Read the guide →Cylinder questions, answered straight
How much does an unvented cylinder cost supplied and fitted?
A like-for-like 150 L replacement starts from £1,640 + VAT (£1,968 inc VAT), cylinder, fittings, labour and disposal included. Larger cylinders and conversions from a vented system cost more; the calculator on this page gives you a guide price in 30 seconds. A real example: a 150 L cylinder supplied and fitted in Great Bedwyn in September 2025 came to £1,981 inc VAT all in.
Do I legally need a G3 plumber for an unvented cylinder?
Yes. Unvented cylinders store hot water under mains pressure, so Building Regulations require the installer to hold the G3 unvented hot water qualification and to notify the work. Will is G3 qualified and WaterSafe (WRAS) approved, and the notification is included in our price.
How long will I be without hot water?
Most of the day for a like-for-like swap; the new cylinder is usually heating by late afternoon. A conversion from a vented system takes two days, with hot water restored at the end of the second day. We tell you the plan before we start.
What size cylinder do I need?
Roughly 35 to 45 litres per person, rounded up for a second bathroom or a big bath. 150 L suits a one-bathroom home for two people, 210 L covers most family homes, 250 to 300 L for two or three bathrooms. We confirm the size and check your mains flow rate on the survey, because an unvented cylinder is only as good as the water pressure feeding it.
Is it worth converting from a vented tank system?
If you have weak showers, a tank in the loft you would rather be rid of, or you are planning a bathroom refit, usually yes. You get mains-pressure hot water everywhere, free up the loft, and the cylinder heats faster. It only works if your incoming mains can supply enough flow, which is the first thing we test.
What is included and what is not?
Included: the cylinder, expansion vessel, safety valves and fittings, discharge pipework, labour, removal and disposal of the old cylinder, Building Regulations notification, testing and a handover. Not included: electrical work for a new immersion supply (our electrician prices this with a certificate), decoration, and any boiler work (we do not work on gas or oil boilers and will recommend a Gas Safe engineer if yours needs attention).
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Ready for proper hot water pressure?
Use the calculator for a guide price, then book a free survey. You get one written fixed price and a date, and we stick to both.