[eldub]

Every so often my drain stops up on the way out to the city's lines. It's very hard to get a plumber out, so sometimes it'll be weeks before that can happen. So here's what I am having trouble with: The line has a tendency to clear itself. So if i get a plumber, the line runs clean as a whistle. Other times it will somewhat clear but I can see the drainage hitting a roadblock and backing up. Other times it will clear on its own and look as if I've had the plumber come out...smooth flow without slowing or stopping. WTH!!???

[LiQuId]

Cracked drainage piping and a fluctuating water table ?????

you should have it camera'd

is there a consistancy to it at all ?? i.e. does it block after a given amount of flow from one or more fixtures? you could attempt to replicate it a few times and see, this would give better insight as to the nature of the problem. The homeowner often knows exactlly whats wrong but doesnt realize it, or have the means to solve it... thats what makes plumbing sometimes a detective type job.

[PrecisionPlumbing]

Seems like you need a repair. Use a sewer camera