Could this be a vent problem??? Please Help

[KCFilley]

Hi,

I just built a new barn and am having possible vent problems with the plumbing but I'm just not sure. I would appreciate your thoughts.

A union plumber did the work on the side for me. He's a great guy but this is the second major problem (drains set too high in concrete floor was first problem and water washes around the drain!). Any way, he's willing to fix the problem but he doesn't know how to or what to try.

The sink is first in line, then the toilet. The vent (now totally open) comes directly up from (above) the sink trap. Next in line is the toilet.

Because the septic tank is small, I told the plumber to daylight the sink drain but he forgot and joined this drain into the same 4" waste line as the toilet. He joined the sink waste line, after the toilet drain.

The problem is if the sink has 2 or 3 gallons of water in it and when it drains from the sink it bubbles up through the toilet.

When the toilet is flushed, it runs ok. However, if 2 or 3 gallons of water are poured into the sink and drained, and the toilet is then flushed right afterwards, the toilet stops up and almost overflows.

Unfortunately, concrete has already been poured over the drain lines. The concrete has heat tubes in it so cutting would be difficult but not impossible.

Do you have any ideas as to what the problem is and how to fix it?

Thanks again for all your thoughts.

KCFilley

[hj]

I hope he put cleanouts in the pipe outside the building. If so, then opening them and observing what happens when the toilet is flushed should tell yo what the problem is.

[KCFilley]

Thanks HJ for your reply. There is a cleanout/pumping pipe that goes directly into the tank.

What should I be looking for and what will it tell me? I'll go out now and check.

Thanks.

KCF

[hj]

Remove the plug from the cleanout. If the toilet flushed properly then, you will know it is an air lock/venting problem. If not then it is probably a plugged pipe under the building, or a poor installation.

[KCFilley]

Hi Hj,

First a review. If no water has run through the sink and the toilet is flushed, the flush is ok. It seems to drain ok. There is no back up in the toilet.

If I drain water through the sink, it bubbles up the toilet.

If I drain water first and then flush the toilet, the toilet backs up and overflows.

Today I removed the outdoor cleanout plug and flushed the toilet. It seems ok (usual). I filled the sink with about 5 gallons of water. When it drained, it again bubbled up through the toilet. Then I flushed the toilet and it did not overflow but it did almost fill the bowl of the toilet.

What is your best guess?

Thanks.

KCF