I have a double sink with disposal that won't drain what so ever. I tried to plunge it with no luck, next I dis -assembled the trap underneath and found no blockages whatsoever ever. My next step was to snake the drain past the trap which came up clean as well. From there I went to the exterior clean out and shoved my snake in there (20') which also came up clean. Thinking maybe my snake doesn't reach the clog I shoved my garden hose in and ran it wide open for a few minutes and it didn't backup at all. Once I reassembled all the piping I poured hot water into my sink to feel how far it was reaching before stopping. The hot water is stopping at the trap under the sink but as I said before it is completely clear. I have a air gap vent which seems to be clear but am not sure how to be completely sure of that.

Any ideas what I should do next before I call a plumber?

Thanks in advance for any help

We sould have to see your drain system, because you seem to be describing a "double trap" problem and a plumber would have to check it and find out how to cure it.

Leave the exterior cleanout open and try using the sink.

With the trap off and a bucket under the disposer elbow and you put water in the sink does the water pass through the disposer?

A plumber has the skills and equipment to get the job done in a matter of minutes, especially with an outside cleanout and a power source handy. If you were trying to use a little hand crank snake, or one that goes on a drill, you might as well stop before you get mad and throw it at something. Drains are best left to the experienced, there is a lot of technique involved.