ISO Class 7 refers to non-viable particulate. I am not aware of any regulation that specifically prohibits sinks, etc in Class 7.
The only specific mention I can find is in the EudraLex for Aeseptic manufacturing, (EudraLex Vol 4 annex 1 para 50) which says: "Sinks and drains should be prohibited in grade A/B areas used for aseptic manufacture. In other areas air breaks should be fitted between the machine or sink and the drains. Floor drains in lower grade clean rooms should be fitted with traps or water seals to prevent backflow."