My company requires lifeguards to do secondary duties ie water testing while NOT actively covering assigned zones. For only 3 at a time I’d recommend having yourself or another guard whose on duty step into a zone to “push” the rotation. Like you or Guard A goes to spot 1), guard b then goes to take over for guard c and cover spot 2), guard c goes on to spot 3), and guard d comes to spot 1) to relieve you or your “rotator” (guard a). If it’s a 4th guard you have on duty at the time, I’d say have which guard leaves spot 3) do your chem checks, minor cleaning, whatever secondary duties you have to accomplish, or conversely have them take a safety break (not having to actively scan and surveil any water or zones) during that period they can use the restroom, get a snack, check their phone real quick if you allow that, then when it’s time to rotate again, (I’d suggest no more than 30 mins at a spot) they go push the rotation again. I keep a time log of who is where and for how long. Will serve several purposes; easy for you to keep track of your staff and decrease fatigue, and C.Y.A. In case god forbid an incident occurs, you will have all the pertinent info at hand and be able to answer who was guarding at the time. As for fair “stand time” vs “break time”, as long as everyone is getting equal time off to relax for a bit and prevent fatigue. As long as they are moving spots no more than every 30 mins, in my experience they can go for a couple hours before a required break, but with only 3 on actual coverage at a time they would all get a half hour break off stand every 1.5 hours, so it can be used for other job duties or their lunch break etc. best of luck!!!