I have a 3 sensor system and after a week of testing, it was 100% reliable.
I use a TM751 and a MS16a sensor for each zone.
They are attached to each other or within a foot distance.
I use a AM466 and a 110 VAC relay for each zone. A-1 (silenced), C-3, and E-3
All 3 relays output 110 VAC in parallel to the primary of a 110/24 VAC transformer.
If any sensor triggers, there is 24 VAC output.
If all 3 trigger, the last one to send an OFF will turn the 24 VAC off.
If everything goes as planned this whole house water control system will be on the local news next week.
If it wasn't for this forum, I would not be writing this post.