We have a project where common water network is feeding to hydrant and portable water. This network is connected to the single fire water tank and suction manifold for portable water and fire water is same. Pumps are separate for fire hydrant and portable water and both pumps are connected to the common water network, where tapping for portable water is taken at the building location from common network.
As per NFPA 22; section 18.104.22.168.1, "Pipe used for other than fire protection purpose shall be entirely separate from fire service pipes and shall extend to an elevation inside the tank above that required for fire protection".
Also in contradiction we noticed in NFPA 20; A.4.27, "A domestic water pump in a dual-purpose water supply system can function as a means of maintaining pressure".
So whether the common water supply network is allowed to serve the fire fighting system and portable water system, if so how it works and what are the provisions to be considered? Please also note in above case same suction is used for portable & Domestic water.
Please clarify above.