Let's go over the rules for taking other people's stuff.
If you want something gone, put it on the boulevard. It's universally understood that anything on the boulevard is meant to be spirited away by whoever gets there first. You can put out a box of expired milk with a sign saying FREE and it will vanish. The people who take it will chuckle over their luck all the way home: idiots throwing away perfectly good bad milk.
The sidewalk is the DMZ, a neutral area. If something is on your lawn, it is your property. If someone comes to steal your sprinkler from your lawn, you can call the cops, although don't expect them to go all lights-and-sirens. You can put a picture of the missing property on a milk carton, but that probably won't help much because someone took the milk carton you left on the boulevard.
If the sprinkler is on the boulevard but it's hooked up to a hose, it cannot be considered fair game for gleaners. No court in the land would convict you if you used a lasso to detain a thief who was unscrewing the sprinkler. The judge might ask where you got the lasso.
"Well, ma'am, I was in the rodeo for 20 years, and learned a lot about using rope to stop varmints and sidewinders. "
"How about lowdown, no-good claim-jumpers?"
"Oh, for those I use a Taser."
But! If you disconnect the sprinkler from the hose, it's free — providing it's within 10 feet of the driveway. Proximity to the driveway is crucial. Just look it up on the Unwritten Rules of Gleaning.