Bathroom sink backfilling?

[Robert Jones]

Home today, built in 1911. 1/2 bath added to the second floor. Old galvanized water lines, old cast iron drain line. Every time something else with a water source was run ie; second floor sink/toilet, dishwasher, tub etc... The main bathroom sink filled with water. I am guessing a venting issue? I guess it could be a main drain issue. Any thoughts? Here are a couple of pics of the area below the main bathroom. Do enjoy the drain for the washing machine, it has a rag stuffed around it on the inside.

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[SWagar]

It is a little hard to tell from your photos whats what. But It sounds to me like the main bathroom sink is not vented or the vent is clogged.

How much water came back into the sink, a sink full or a trap full?

If there is only a trap's worth of water in the sink. Air pressure may be forcing the water in the trap back up into the sink.

If there is more than that, I'd suspect that the drain line is also pitched toward the trap instead of away from it.

Do you have any more photos? Where is the sink drain line in the wide view photo?

[Robert Jones]

Scott,

It becomes a sink full of water(would actually over flow if not for the bailing that the realtor was doing). The drain line is the angled long plastic run behind the 2 galvanized lines in the wide view photo. I could not access the attic on that side of the roof to check the vents. There are vents exiting the roof.

Thanks

[SWagar]

Well from that description, sounds like the drain line is pitched incorrectly and is holding water. When another fixture empties water into the system, air or water pressure is forcing the trapped water back up into the sink. But this could also imply that there is a lack of venting all though the house. How well did this sink drain? Do you do a sink overflow drain test and then empty a full sink full all at once ?

Maybe, the drain line is marginally or even correctly pitched and has built up gook which could be causing it to hold water. Just a thought.

Added later...

It could also be that the main drain is clogged or occluded so that water backs up in the entire drain system and the bathroom sink is the

point of relief.

I think it's now PLUMBER o'clock !!

[Robert Jones]

Thanks Scott,

I do the overflow drain test and in this case, it was done a few times. My initial impression was venting. Either way, I definitely informed my client that a plumber is needed for more than just that issue.

Thanks again Scott

[Tom Raymond]

Rob,

Was it on a septic system? What you described sounds like either a clogged tank filter if it's a newer system, or a clog between the tank and the leach field.

Tom

[Robert Jones]

Hi Tom,

The home was run into city sewer system.

[Tom Raymond]

I've had to dig up two systems in the last two years that were behaving very much like the one in the OP, just thought I'd share my misery, err..experience.

I would be leaning toward a blockage or improperly pitched drains then, missing vents tend to syphon traps not back them up. With the high quality work there I wouldn't be surprised if you find some horizontal tees or wyes too.

Tom