Where can I find replacement for my 6" siphon valve?

Do by any chance mean an anti-siphon hose bib?

If you are talking about an anti-freeze (and anti-siphon) outside faucet then you need to determine the manufacturer of the valve to find replacement parts... should be marked or imprinted on the valve itself... ;)

Mark

See the image below if this is what are talking about you can buy at Lowe's, Thanks.

John

Outside faucet replacement parts are VERY specific and are not interchangeable. Ricardo needs to determine the manufacturer and then go online to find the manufacturer and/or a local distributor to be able to fix his issue. Once a name brand or manufacturer is known finding replacement parts should be easy!