According to government protocols, any vessel holding more than 15 litres of high temp water under pressure should be placed by a skilled specialist. A G3 and CITB certified expert should take care of vented & unvented hot water cylinder installation. You cannot afford to make a mistake during hot water cylinder installation. A single mistake can lead to a lot of damage. The installation process requires intense pressure and involves hot water. You should not carry out the installation yourself. Call one of the best hot water cylinder installers to ensure the work gets done without any faults. You must notify your local building control department that you are installing an unvented system before doing so. This is due to the possibility that the property will require the installation of valves and pipework for pressure relief that will vent outside the structure.