Weird plumbing

[messmaker]

I have a slow shower drain in the basement of my ranch style house. I have run a 25 foot snake through it and I still see a slow drain. None of the other drains seem to be affected. When I have had a clog in the main sewer drain in the past, I have had a backup in the tub in question. It has not happened. I am lost.

[petertay15]

Is this a city sewer, or to your septic? So the first 25 feet are okay. What lies beyond? Could a tree root be in the pipe?

[crokett™]

Is the shower the closest to where the main drain leaves the house, or furthest away? is it somewhere in the middle? does it tie into a a branch line, or go direct tot he main line? if a branch, is there a toilet on that branch?

[messmaker]

Is the shower the closest to where the main drain leaves the house, or furthest away? is it somewhere in the middle? does it tie into a a branch line, or go direct tot he main line? if a branch, is there a toilet on that branch?

I am on a septic which has just been replaced in the last 18 months. It is very close to the main line. I would say less than 5 feet. It was put in on a basement remodel about 20 years ago,

[Phil Thien]

And just to be clear, this is a new problem, the drain previously ran fine?

[jamesglenn]

And just to be clear, this is a new problem, the drain previously ran fine?

My first thought as well. 

If this has been an ongoing problem and the drain seems to be clear, then I would next suspect the vent line is either obstructed, not installed correctly, or not installed at all?

[messmaker]

My first thought as well. 

If this has been an ongoing problem and the drain seems to be clear, then I would next suspect the vent line is either obstructed, not installed correctly, or not installed at all?

It has worked fine for years. It is the shower I use after work so it gets plenty of tough use, especially during the summer. I will check the vent today. I have not checked yet because I thought if it was a vent, it would have showed up in another drain.