"ashroyer" wrote in message
http://www.watts.com/pdf/ES-800M4QT.pdf

But they are more expensive and much bigger.

There are no city codes in my area requiring the use of a backflow
prevention device though I'd still like to put something in.

The purpose of a bfp device is to avoid contamination of the water supply.
Forget codes. If there was a backflow just after you fertilize the lawn,
your house is the first to be contaminated. Still want to save a few bucks?

If you can afford to put in a sprinkler system and have a fancy lawn, don't
be a cheap prick when it comes to protecting your family. Use the right
device.