I know from our water butts it can vary greatly depending on the wind direction. On a good day one 210L butt can fill in less than half an hour.
We had about 5cm rain here in Sussex, assuming a 50 square metre roof then your 5 ibcs could be over half full.
Edit to say you probably had less rain but a bigger roof, so about the same guess.
We had about 5cm rain here in Sussex, assuming a 50 square metre roof then your 5 ibcs could be over half full.
Edit to say you probably had less rain but a bigger roof, so about the same guess.