My Vetrano Vacuum breaker started hissing, so I removed it, took it apart and soaked it in white vinegar for a couple of hours. I put it back together and it sill is hissing. Searching the topic, I found the attached expanded diagram and a discussion suggesting replacing an o-ring. I found no o-ring when I took the vacuum breaker apart. I expect it had disintegrated. Can someone tell me where the o-ring goes in the vacuum breaker? I plan on purchasing a new one, but would like to get my Vetrano working while I wait for it to arrive and hope a new o-ring will work. Thanks.

The arrow for item No. 1 is pointing directly at the o-ring.

See this: O-rings & Copper Sealing Washers