Irrigation valve type when water supply at bottom of slope?
I live on an acre lot, the backyard slopes down probably 10-15'+ in elevation from where house exists at highest point on property. The water from the city originates up at the higher elevation where house is.
There are two hose bibs installed at bottom of lower yard (at lowest point), they're elevated about 2' above the ground there so still way below the elevation the house is at. The lines for these and the hose bibs themselves were installed by a previous homeowner and are long runs from house down the slope (maybe 100').
The lowest part of slope is grass with two rotor sprinklers down there aiming up, the rest is planters some of which start at bottom of slope and head up part way towards elevation of house. I have an elaborate drip system running in the planters I describe. The irrigation system is active May-Sep (not needed Oct-April due to rain). I've been using portable battery-operated irrigation timers for these circuits but am tired of them being unreliable. I want to switch to using irrigation valves connected to a timer.
So I read about anti-siphon/backflow prevention valves needing to be installed higher than the highest sprinkler. Based on me using the hose bibs at bottom of hill and the drip system watering plants higher on slope than where hose bibs are, I'm trying to figure out my options.
I know anti-siphon/backflow are designed to prevent potentially contaminated water from flowing into drinking water supply but with hose bibs at bottom of slope 10-15' below elevation of house where main house water supply is, is this a concern? Should I use valves that are not anti-siphon? do they make these anymore? I really want to dump the portable battery-operated timers, I hate them, have had unpredictable problems like them opening then staying open never shutting off (imagine if happened when I go on vacation!!).