Yes, you can replace a vented water cylinder with an unvented water cylinder.
The only boiler that can be installed as part of a vented water cylinder is a regular boiler, also known as a conventional boiler.
If you wish to have a system or combi-boiler instead, you will need to have an unvented water cylinder installed as there is no need for water tanks in the loft to supply the water. Instead, they take water directly from the mains.
You can find out which boiler is right for you using our handy 2022 boiler guide.