Sprinklers in City and Shallow Well - Back Flow?

[Linescreamer]

Can I use a standard $25 1" check valve on my city water supply to prevent back flow? My sprinkler control valves are supplied by both Shallow Well and City water. During drought I will close the ball valve on the Well supply and open the ball valve on the City supply. They would both feed into a 1" PVC T and then the control valves. Planned on placing the "inexpensive" check valve prior to the city water ball/shut off supply.

 

[Linescreamer]

Looks like the right way to do this is to install an RPZ valve. Which is crazy expensive! Can't I just use PVC Ball valves? Shut water supply from well and open water supply from City? The City water pressure will push the residual Well water out of the sprinklers in a couple seconds. No way will the Well water contaminate the City water when the Ball valve is closed. I would also need to somehow bypass the pump start relay when on city water. How should I set this up?

 

[Sponsor]

 

[Fitter30]

No, don't know Florida code might just need a double check or a vacuum breaker. Need to check with your water company or plumbing inspector.