Tub drains very slow

Question

I've been trying to fix a extremely slow draining bath tub for awhile, but still can't get it right. Here is the work that's been done:

1. Ran 25 feet of cable from a power snake (drill powered) 3x's. Results: some black gunk on about the first 12 inches of line and a few strands of hair. No change.

2. Plugged the overflow valve and plunged the hell out of it. Results: (this is interesting) removed 2 handfuls of acorns that the local Woodpeckers deposited down the roof vent! I continued until no more could be removed. No change.

3. Pushed an expanding pulse bladder down the roof stack about 7-8 feet and ran it for 5-10 minutes. Results: no water backed up from any other drains. Opening the nearby clean out I could hear water running! But still No change.

The sink that is in the shared bathroom drains perfectly. There's a clean-out 5 ft. outside the window. I've opened the wall were the drain is located, but it takes a direct 90 into the slab. One of my guesses is the drain stopper used to plug the drain for a bath some how broke off from the lever. It's an unbelievable plumbing problem that has me completely stumped.

Answer 1

It may be time to call in a professional with a piping inspection camera system or rent such unit yourself and do an inspection of the drain line from the tub down into the sewer. This would clear up any concern that there may be a blockage or loose article that has entered the drain system.

The report that you had already removed a bunch of acorns from the roof vent line leads to concern that this vent is still clogged to the extent that free air movement below the tub trap is not being allowed and that the tub drain ends up with an air lock and thus cannot drain properly. It may be well to also scope out this line down from the roof with the piping inspection camera. (Do also make sure to install a screen on the vent pipe to prevent insertion of more acorns).

Since you already made attempts to clear the roof vent line is it somewhat possible that the vent was never installed correctly from the original construction and that this tub never drained properly. If that is the case then it may become necessary to install an additional vent pipe. The need for this of course could be eliminated if it was known of this particular bath tub did drain properly in the past. That could come from your own experience or consulting with previous owners.

Answer 2

Measure the volume of water draining nicely before it goes into "slow drain mode" e.g. have some 1 or 1.5 ltr bottles filled with water and flush them into the bath tub. A drain pipe of 50mm diameter needs ca. 5m to be filled with 1 ltr of water.

To test your theory about drain stopper test how the sink drains while your tub is in "slow draining" mode.

Answer 3

You say it IS draining, only slowly? Two things:

1. Try a LARGE volume of water ALL at once. Like a bucket. Tubs have U-Bends, and you need to provide sufficient volume of water to overcome that and start a syphon.

2. If the sink IS draining but the tub is NOT? Try a shop vac. Block off the overflow valve and ram the hose right onto the drain. Seriously. If the sink is good but the tub really is backed up, then your clog is right next to the tub drain.

Full disclosure: I'm not a plumma', I just flush a lot.