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Installation Cost Guide: Vented & Unvented Hot Water Cylinders

If you’ve got a system or a conventional boiler, your water is pre-heated and stored in either a vented or unvented hot water cylinder. In our 5-minute guide, we’ll explain these 2 types of cylinders, touch on the best brands, and discuss the typical hot water cylinder cost to install.

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Do You Need Vented or Unvented Cylinder Installation?

There are 2 types of hot water cylinders:

  • Vented
  • Unvented

The end goal is the same, but there’s a few minor differences. Sadly, you don’t get much say over the type of cylinder you need — your boiler type will dictate whether you need vented or unvented cylinder installation.

What Is an Unvented Hot Water Cylinder?

An unvented cylinder typically works in conjunction with a system boiler, although some people like to have an immersion heater in their cylinder in case the boiler fails.

Modern unvented heaters are highly complex, but all function in roughly the same manner:

  1. Cold water from the mains fills the cylinder.
  2. Hot central heating water from the boiler travels through the cylinder via a coil, which heats the cold water — this function separates the domestic tap water from central heating.
  3. As needed, the cylinder distributes hot water to the taps.
  4. For safety, there’s an expansion vessel that helps the cylinder vent pressure when it gets dangerously high.
  5. As some hot water gets released, the cylinder once again fills up with cold water from the mains.
  6. The cycle continues.

Since it gets water from the mains, an unvented cylinder is the perfect choice if you don’t have space for a water tank, or you’re converting your vented system into an unvented one to save space.

Of course, the downside is if mains water is off for whatever reason, you won’t have hot water — except for what’s left in the tank.

What Is a Vented Hot Water Cylinder?

Vented hot water cylinders are designed to work with conventional boilers. They’re somewhat similar to an unvented ones, except they get their water from a cold water feed tank — which is usually up in the loft. To relieve pressure, a vented tank relies on a vent pipe to send excess water back into the cold water storage tank.

So, if you’ve got a conventional boiler with a water tank in the loft, you’ll need a vented boiler. And when you get one, make sure it’s in an area of the house that doesn’t go below freezing in the winter, or you’ll have no hot water at all. That said, a cylinder tank jacket will usually keep water from freezing 99% of the time.

Hot Water Cylinder Installation Costs

Below, we have some rough cost estimates for both vented and unvented cylinder installation.

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Unvented Cylinder Installation Costs

Unvented cylinder installation can vary in price between £400 and £1,600+. Here are some factors that affect the cost of replacing a hot water cylinder:

  • How big is it? If we take Worcester Bosch as an example, they have the SC-90 unvented cylinder on offer for around £600. But 90L is extremely small for most properties. Now, if we check out their SC-300 (which is 300L), we’ll see that it’s a whopping £900 – that’s £300 more you’ll pay to get a higher capacity cylinder.
  • What brand is it? We based the example above on Worcester Bosch — the crème de la crème of the boiler world. There are other, far cheaper options available, and generally, you can expect to pay anywhere from £400-1,250 for unvented cylinder installation.
  • Do you have a cylinder installed already, or are you getting one for the first time? The figures above assume a straightforward, like-for-like swap: old cylinder out, new cylinder in. But what if you didn’t have a cylinder before? Now things are more complicated, because you’ll need to fit all the required pipework.
  • Will you move your new cylinder to a new location? If your new cylinder isn’t replacing the old one in the exact same spot, your installers will have to reroute the pipework. So, whether you’re installing a hot water cylinder for the first time, or moving the replacement to a new location, you can expect to pay another £250-350 for labour.

Vented Cylinder Replacement Costs

Vented cylinders are far less complex than their more modern, unvented peers. And so it’s typically cheaper to install them: Whilst unvented cylinder installation can set you back over £1,600, a new vented cylinder shouldn’t cost more than £600, including labour.

As we’ve said before, unfortunately, the type of cylinder you need isn’t really up for debate — it depends on the heating setup you’ve got at home.

When You Should Be Replacing a Hot Water Cylinder

Unless you’re converting your heating system, moving the cylinder, or find that it’s leaking, there’s a good chance you needn’t be replacing your hot water cylinder.

And luckily, manufacturers of both vented and unvented hot water cylinders will provide long warranties. For instance, Worcester Bosch offer a 25-year warranty on their Greenstore cylinders. So, before you commit to replacing a hot water cylinder, check to see if yours is covered by a warranty.

The Best Hot Water Cylinders

There’s a tonne of top quality brands selling hot water cylinders. If you’re looking for a replacement, here are the best cylinders we’ve come across are:

Joule Cylinders

We’ve covered the Joule Cyclone Cylinders here. They are fairly new player to the hot water cylinder market, but they are high quality and reasonably priced. 

Worcester Greenstore

Worcester offer a huge 25 year warranty on their Greenstore cylinders. And, they start as small as 90L with the SC-90, so there’s a cylinder for every type of property.


Gledhill offer a fantastic range of cylinders, and are cheaper than Worcester Greenstore. They’ve also got a good range of direct and in-direct copper cylinders.


Stelflow are made by RM Cylinders. In terms of price, they are on par with Gledhill, but slightly more expensive than the Joule Cyclone we mentioned above.

Finding A Hot Water Cylinder Installer

We’ve got contacts across the UK that fit cylinders, boilers and central heating.

To get free quotes, click here.

Any Questions?

We’re always happy to help.

If you have any questions regarding hot water cylinders, installation costs, or even advice on whether a quote you’ve received is reasonable, please leave a comment below and we’ll get back to you as soon as possible.

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  1. SUSAN BROOKS says:

    Hello, my gledhill electric boiler is not working properly, i have had lots of new elements, it works for a while and then breaks down again. I may need to replace it, it is around 20 years old, any suggestions ?

    1. heatingforce says:

      Hi Susan,

      What Gledhill is it? What volt elements have been used? Have the thermostats been replaced alongside the elements? Is the outflow being replaced quick enough (i.e. the element is covered by water at all times)?


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