Someone did a lousy job installing my front yard sprinklers. It's all made of 1/2" copper with no vacuum breaker or backflow limiter. There's a pipe that comes out of the house exterior wall with a T, one end leading to an ordinary valved garden hose spigot, the other leading to a valve and into the ground.

My problem is that on the valve on the pipe into the ground, there's a side spigot. When I open the valve, all the water goes out this side spigot. It looks like 1/8" or 1/4" with some wide gauge and well-worn threads. The valve unit looks like sand-cast brass. The sprinklers won't work with the valve off and with the valve on, there's a constant stream of water pouring out.

I'm guessing this is some sort of a pressure relief or backflow limiter kind of deal that's missing a part. I went to my local big-box hardware store and the nice gentleman in the orange apron said it's an aerator cap, they're out of them because the contractors always come in to steal them off the valves, that they're only made in Italy, and I'd have to go to a plumbing store to get one.

I'm willing to do more than just screw a cap in the right place, but I fear there's little I can do to mend a sprinkler system made of 1/2" copper without a complete overhaul. Does anyone have any suggestions? Is this a part I can find somewhere? Is it called an aerator cap? Is this a solution, even if a bad one?

Thanks in advance,

Stephan Samuel