Which material is most appropriate for underground firewater main (high TDS content in firewater), RTR or HDPE? What are the appropriate design guidelines, since NFPA 24-2010, Table 10.1.1 does not cover such materials?
The latest NFPA 24 standard permits HDPE pipe as long as it is manufactured per AWWA C906. Otherwise use PVC pipe (AWWA C900) if plastic piping is required. Cement lined DI pipe is the best non plastic alternative.
Thanks for the reply. Why NFPA 24 didn't include RTR in the 2016 edition?. RTR pipes are used in fire water system and are FM Approved. Is it preferable to use HDPE pipe instead of RTR (note that cement lined is not a choice in our case as we have experienced many issues with this type of material).
NFPA 24 allows piping materials other than those specified in table 10.1.1.1 if listed. So technically listed RTR pipes can be used. The reason NFPA 24 does not allow unlisted RTR pipes is because they don't have the long reliability track record of the other pipe materials.
In my experience, all piping material (permitted by NFPA 24) in general have roughly similar performance. Preference of one type over another will depend on soil type, supplier's pricing and the contractor's installation method.
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