Rachis Flow Meter Installation

[RLMELL]

I'm a homeowner in California and first time poster. I'd like to install the Rachio flow meter. Flow meter must be installed above ground on the downstream side of the back flow preventer and requires a 3/4" or 1" pipe. Pipe must be Copper, PVC, PEX or SDR9 poly. My back flow preventer is connected to 1-1/4" galvanized pipe. I was wondering if it is possible/meets code to downsize the downstream pipe off the back flow preventer to 1" PVC, or if that would somehow affect the performance of the back flow preventer? I would assume it wouldn't given that the in ground pipe that the back flow assembly is connected to is 1", but I don't know. I've attached a picture of the back flow preventer if that helps at all. Thanks
https://www.rachio.com/wireless-flow-meter

 

[WorthFlorida]

Looks like s nice flow meter device. A 1-1/4 galv. and a 1” PVC SCH 40 have almost the same inside diameter and there be no problem changing pipe size. Do use SCH 40 as much as possible when replacing the galv. pipe.
https://www.pvcfittingsonline.com/resource-center/pvc-pipe-dimensions-18-through-24/

Code requirements after the backflow preventer pretty much ends for potable water supply. After it irrigation code requirements kick in. You’ll need to look into California irrigation laws.

In Florida, two off hand is, a rain detector is require on the controller and no sprinkler is allowed closer than 18” to a dwelling. The only only plumbing type code that I know of is on a reclaimed water supply after the meter, such as I have, no spigots are allowed and not be connected in anyway to your home potable water system.