Building services, such as water, ventilation and electrical systems, can all degrade over time through mechanical or chemical processes. CIBSE guide M is widely used to give estimates of component and system life expectancy; however, actual life expectancy can vary greatly from these estimates depending on how the system was commissioned, used and maintained.
In many retrofit cases, to achieve the best possible result it would be preferable to remove an existing system and start again — from an engineer's perspective, this would give the freedom to perfect designs. However, in most cases, this isn’t possible, due, among other things, to budgetary restraints.
It is often necessary to use parts of an existing system and repurpose parts to provide an extension to or potentially a whole new service. This pushes ingenuity and is a tremendous accolade to the modern engineer. However, without accurate validation information, even the most adaptable engineer can end up with a system that falls short of client expectations, or worse still fails completely, costing all parties involved.