Back Flow Prevention

Hello all,

I recently purchased a new home and began working on the landscaping and drip irrigation system. Aside from the many leaks, I discovered that anti-siphon valves had been installed below ground, in a box. Worse still, my property has extreme grade changes and 3 of the valves were watering up-hill (as much as 15-20 feet), so water was spilling out of the valves the entire time they were running.

So, I had a plumber install a RPZ back-flow prevention device and am now going to work on the valve manifold.

My question is, do I need anti-siphon valves now that I have the proper back-flow device? Will the water stored in the uphill lines after shut-off cause an issue for the valves (back pressure)? Should I add a check valve to these valves?

Thank you,

Looking to learn from others but typically my sprinkler heads will drain excess water from the lowest point in the zone when they shut off. I only have a backflow prevention valve (required by the city).

We do not have and are not required to have an anti-siphon or back-flow (we have irrigation instead of culinary). I put an excess of king drains, so it drains before the lowest point. A relatively small amount drains at the lowest point. I definitely want my drained so they hopefully will never freeze. I do not think back pressure would cause an issue unless it can ever freeze.