If an oil storage tank is removed from its base temporarily, for example to repair the base and piers, would I be allowed to reinstall the original oil storage tank as it was before or would I have to treat this as a new installation?

Yes, but OFTEC would recommend that all oil storage tank installations should be compliant with regulatory requirements and industry guidance. However, the installation of a ‘new’ or ‘replacement’ oil storage tank would fall within the scope of the Building Regulations.