Does this require backflow prevention, and who pays for it?

Certain configurations may require backflow prevention devices, though not every application will. This is typically up to the local water provider and plumbing codes; there is no blanket requirement. Often backflow precention can be avoided through design such multipurpose systems, where the same plumbing feeds both sprinklers and domestic fixtures, or passive purge systems, with standalone piping serving the sprinklers and one toilet. Under the IRC, a backflow preventer is not required between the sprinkler system and the home's water distribution system if the system complies with NFPA 13D or IRC P2904, uses IRC-permitted piping materials, contains no antifreeze, and has no fire department connection. Where a device is required, the homeowner pays for it and for periodic testing, both of which are economical.