  The CHIPS R&D project aims to develop affordable large-scale water Cherenkov
neutrino detectors for underwater deployment. In 2019, a 5kt prototype detector
CHIPS-5 was deployed in northern Minnesota to potentially study neutrinos
generated by the NuMI beam. This paper presents the dedicated low-latency
triggering system for CHIPS-5 that delivers notifications of neutrino spills
from the Fermilab accelerator complex to the detector with sub-nanosecond
precision. Building on existing NOvA infrastructure, the time distribution
system achieves this using only open-source software and conventional computing
and network elements. In a time-of-flight study, the system reliably provided
advance notifications $610 \pm 330\text{ ms}$ prior to neutrino spills at 96%
efficiency. This permits advanced analysis in real-time as well as
hardware-assisted triggering that saves data bandwidth and reduces DAQ
computing load outside time windows of interest.
