Warship washdown and fire suppression share the same water network

Is a frigate's CBRN washdown sprinkler system also part of its fire-suppression system?

Yes. The washdown and fire-suppression functions are linked into the same general water-main system.

The sprinkler system used for chemical, biological, and radiological protection is also part of the ship's fire-suppression arrangements. Both functions draw on the same broader water-main network rather than requiring wholly independent machinery. That shared infrastructure lets a warship wash contaminants from exposed surfaces and support damage control. One water system can therefore serve several emergency roles.