1966 Safari Tub will not drain although the pipe to the back is clear?

[tonupjonnie]

Hi!
I have water backed up in my shower drain of my 1966 Safari. I have ran a small sink snake though all the way to the dump valve exit at the back but the water still sits there? Wandering why it is not draining, not even slowly. This trailer has not been used in 22 years. The sink was the same but was easy to clean as the p-trap is easy to get to and has a drain plug, out of this came several old q-tips so I suspect there is who knows what in the shower drain. Thanks in advance.
Jonnie

[cwf]

I am guessing the vent is clogged. Does the water come out of the tank when you open the waste gate? (of course you want to be connected to sewer...)

If you get a 'glug' sound and can hear air pulled from the shower drain, then you can bet the vent line is clogged. Sometimes critters nest.. or just 'buildup' happens