8.1 anti siphon valve

[drifter]

Thanks for the reply.  I do not see anything on the tank under the access hatch that looks anything like the units when I do a search.  There is a shut off valve on the top of the tank, is that normal?  My owner's manual shows this valve on the bulkhead behind the engines where the fuel lines come out.  I can attach a photo later if that would help.
Dick