New rooftop helipad located on a clinic type B that is new. The clinic has an elevator shaft that is used for hospital ER type I occupancy. The vendor performing the test for fixed foam system wants to use just water to show coverage is at least 95% and than plug the outlets and turn foam system on and collect foam discharge rate out of drain to ensure it meets the correct percentage 0.10 gpm/ft2 for AFFF. The hospital and general contractor are concerned with the foam all over the roof. Need some help with this please.