I would disagree that UL listed piping is required unless I can be proven otherwise. I come across this time and time again where people "add" requirements that are not explicitly required. I doubt that anyone on this forum will be able to answer this for you. You need to ask yourself the following questions.
1) What is the code of construction that you are building this to? Is this code a legal requirement, or has it been adopted as good engineering practice for the system that you are designing?
2) What jurisdictional requirements are in place? Is there a fire code that you are required to be in compliance with? If so, does the fire code reference different codes of construction, or NFPA documents as mandatory requirements?
3) In the case of a firewater system, the insurance industry often plays a big role. Do the insurer's of the plant require that UL/FM approved piping and components be used for fire protection systems?
Blatantly pulling specifications of the internet, and using them without questioning if they are applicable to your particular situation is a dangerous practice. We routinely waive the requirement for UL/FM approved components where we can show that it is not required. Additionally, as you begin to design larger diameter systems, you may find that all of the components may not be commercially available, and specifying UL listed components could end up costing you a lot of money...
Hope this helps.