Are you all set to buy a Worcester Bosch system boiler with unvented cylinder – with just one hitch?

If you’re not sure which is the best unvented cylinder for you, you’re definitely not alone. You may find yourself looking at what’s out there and wondering; is there really any difference? Should you be paying extra for the same-brand cylinder, or will they all do the same job?

As an experienced engineer, I’m going to do my best to answer that question. However, I’m going to list only the best unvented cylinder brands on the market in this blog – there are others, but they tend to be less reliable, and I’m not going to recommend anything I’ve had troubles with myself in the past.

So, let’s take a look at the top unvented cylinders to fit with a Worcester Bosch system boiler.

1. Worcester Bosch Greenstore

Now, this might seem obvious, but Worcester Bosch is probably always going to be my first choice – with the odd exception (more about that below). So, if you’re about to buy a Worcester Bosch boiler, filter, and controls, I’d definitely consider opting for a Greenstore cylinder to go with it. That way you can take advantage of a great, package deal.

Go for a Worcester Bosch accredited engineer, and ask if they can give you a deal which includes a longer guarantee on your boiler. You should get 10 years.

The other reason I’d consider a Worcester Bosch Greenstore? Well, having a Worcester Bosch boiler combined with a Greenstore cylinder and integral diverter valve makes for one of the most efficient systems you can have.

Best for: Package deals and a super efficient system

2. Megaflo

Now, let’s take a look at Megaflo. I find engineers tend to talk about Megaflo when simply referring to unvented cylinders in general now. A bit like referring to all vacuum cleaners as ‘hoovers’. This is because the brand is probably the biggest household name when it comes to unvented cylinders.

According to the Megaflow website, their cylinders are constructed from duplex stainless steel, and because of this they offer a “superior resistance to corrosion”. However, the same applies to most modern unvented cylinders, including Gledhill which is next on the list.

Another good point is that every Megaflo unit goes through a very thorough testing process in the factory, where the pressure is increased to 15 bars – that’s five times the usual operating pressure for these cylinders.

Best for: Brand name, and peace of mind

3. GledHill

Gledhill is one of my top picks, as they offer unbeatable value, and excellent quality. They’re manufactured in the UK by a company that’s been specialising in the production of all types of cylinders for over 70 years, and they offer the lightest unvented cylinder on the market. Their product range is great, and they offer horizontal cylinders that fit where other brands don’t.

In fact, they even go one step further and offer custom-made unvented cylinders. This brand has actually won me a job or two in the past! I can always get hold of them when needed, and they also offer a great guarantee. They’ve never given me any problems.

Best for: If you need a horizontal or bespoke cylinder, or need great value for money

4. Santon

Finally, we have Santon. The biggest reason this brand has made the list is due to its extra-long 30-year guarantee. It comes in at around the same price as Megaflo, and they offer two unvented cylinders in their range (so not a patch on the likes of Gledhill). They’re manufactured to very high standards, and their units are extremely resistant to corrosion, making for an extra long life expectancy.

Still, just like all of the other cylinders on this list, the guarantee doesn’t actually cover the cylinder itself. It’s actually 30 years warranty for the pressure vessel. So, always be clued up about exactly what you’re buying!

Best for: If you need a 30-year guarantee

Advice from an experienced engineer

When fitting a Worcester Bosch boiler, I’d always offer the Worcester Bosch Greenstore cylinder, along with filter and controls to create a good, package deal. And combined with the integral diverter value, it makes for one of the most efficient systems around. However, it’s up to you if you want to pay that premium price. There are other brands of cylinders out there, and all of them will work with your boiler.

I’ve fitted this system for a customer who had five children, and she was completely over the moon at how much water she was able to get, and how fast it got hot. Her old system would take around an hour or hour and-a-half to heat up. With the Worcester Bosch Greenstore and integral diverter valve, it took just 20 minutes to heat up again after she’d filled a couple of baths.


I hope this blog has shed a bit more light on the top unvented cylinders to fit to your new Worcester Bosch boiler. A Worcester Bosch Greenstore cylinder may be the most obvious choice, and when combined with the integral diverter valve, it can be one of the most efficient systems around. This is what I’d usually offer to my customers.

However, if getting a good package deal isn’t important to you, or you want to save some money OR get a horizontal or bespoke cylinder, I’d highly recommend going for Gledhill. They offer unbeatable value for money, along with very reliable unvented cylinders.

Do you have any questions about the top unvented cylinders? Let me know in the comments. I’d love to hear from you!