Preparation is key! Select a PVC guttering system that meets the design flowrate of your roof. As well as normal levels of rainwater, an eaves gutter system must be able to cope with intense rainfall lasting at least two minutes. Visit British Standard BS12056 and you’ll see how to work out the amount of rainwater (in litres per second) that could run off your roof.Replacement projects - When it comes to replacing PVC guttering, it’s only natural to consider “like for like” as the most sensible option. However, you should consider the greater frequency of storms and increased rainfall we now experience and modify your system’s capacity as a positive precautionary measure.