Our plant has been using these for about 10 or 12 years: https://www.mcmaster.com/water-leak-diverters
They have these from 3' X 3' up to 20' X 20', have a standard 3/4" GHT fitting in the center and grommets at the corners. With almost 2 acres under a flat roof, we keep half a dozen in different sizes, several lengths of hose, hose repair fittings and a few empty plastic 55 gallon drums for collection.