I was installing a new electrical hookup for a disposal last week and ran across this. The supply for the old disposal was run through this and then to a snap switch inside the sink cabinet. The home was built in the 1870's and I was told the kitchen was added around 1900.
This switch was incorporated in the cold water supply line under the sink. I'm interested in what purpose this served at one time.
My guess would be a pressure switch for a well pump. Back in the day they would have used a shallow well pump and since there would be no need for running water other than in the kitchen, the switch was under the sink.
I wish I had a dollar for each one of those that I've removed.
When the Insinkerator was invented back in 1927, they were afraid that folks, not being accustomed to garbage disposers wouldn't remember to run cold water and wanted to be sure that it could not turn on unless there was water flow.
Good answers above .. I would tend to think it's an electrically controlled valve, why ... ? maybe it was cheaper or less maintenance than having a mechanical valve. less effort thats for sure .. now I've seen the reverse with air switches whereas the air engages a relay for the power but water doing that would be pretty weird .. unless it was to act as a type of flow switch maybe a signal light went off when water flowed .. strange but somewhat in guinness.
Anyone claiming to know everything about Electrical, is wrong.