Tub that won't drain - clogged vent pipe?

[aphex732]

I have an old cast iron tub that fills up with water and drains very slowly when the shower is on. It has an old style cleanout outside the tub as shown in these pictures:

https://imgur.com/a/1U0qm

When the cleanout is in the fully closed, normal position the tub does not drain. As soon as I open the cleanout, the water rushes out and the tub drains perfectly.

Is this an issue with a clogged vent pipe? The sink and the toilet in the bathroom seem to work perfectly and drain/fill without issue. If it is, what's the best way to fix?

Thanks for your help!

 

[Reach4]

Is this an issue with a clogged vent pipe?

No. That is easy. The hard part is fixing the slow draining.

Look for a clog somewhere. The problem could be a clogged drum trap. What does it look like in the basement or crawl space below that? Drum traps were meant to be cleaned out. Newer traps are designed to have stuff move through.

I might consider shoving a Brasscraft drain bladder, with hose, down that pipe that you pulled the "drain" piece out of. I am not a plumber.

 

[Sponsor]

 

[Kreemoweet]

I believe that's how the tub was designed to operate. That "cleanout" thing is the stopper.
Vents seldom have anything to do with drainage slowness, they are to protect traps
from siphonage and to keep the drain system "aerobic".

 

[aphex732]

I believe you're right - thanks for the advice!

 

[WorthFlorida]

As you stated in the pictures, when it is in this position (fully down) it does not drain. I think that is correct. you use it to fill the tub up with it down, as a stopper, then lift to drain! You're calling it a clean out, its not, its a first generation stopper.

 

[Orangewood]

https://deabath.com/Original/SW_page/sw_page.html

 

[WorthFlorida]

A nice find.