New sink drains fine for a few minutes but then backs up

LanceT

My brother-in-law gutted our bathroom and re-arranged some plumbing so we could move the location of the tub, toilet, and sink. Tub and toilet work fine, but the sink backs up and drains VERY slowly after running water down the drain for a few minutes. When I pulled the trap off of the tailpiece to see what was going on, some water popped out like there was some sort of suction going on or pressure coming from further down the drain.

The attached image is the only one I have before walls went up. The vent and drain shown here meet up with the tub vent and drain behind those shelves on the right side of the screen. Like I said, tub and toilet have not given us any problems. Is there not enough slope in this vent? Is it too far from the vertical portion of the vent?

What else could cause it to back up and drain VERY slowly after draining fine for several minutes?

Thanks!

JUGHNE

Do you still have access to under the floor where tub and WC tie in? Pictures of that would be helpful.

Abracadabra

Did you try rodding out the drain? The clog could be down the line maybe 6-7". What you are seeing the the clean PVC pipe filling with water. After it's full, it start showing up as backing up into the sink.

Paul48

If you need to temporarily block a DWV pipe, always use paper, not cloth, as in the picture. If it gets forgotten(maybe?), it can be a pain. Paper breaks down.

LanceT

JUGHNE said:

Do you still have access to under the floor where tub and WC tie in? Pictures of that would be helpful.

Unfortunately, I do not have access anymore.

Abracadabra said:

Did you try rodding out the drain? The clog could be down the line maybe 6-7". What you are seeing the the clean PVC pipe filling with water. After it's full, it start showing up as backing up into the sink.

Not yet. I thought about trying this, but just haven't gotten around to it. It's unlikely since it's all new piping, but I suppose it's possible one of the kids put something down there.

If it is a venting issue, will one of the mechanical vents that goes under the sink resolve the issue?

JUGHNE

Buy, borrow, rent a small hand rodder, it needs to be pretty flexible with the 90 at the sink and the equivalent of a 90 at the vent. It looks like you have only 4' to the vent fm sink. Maybe the rag is at the vent 90. And there could be a Tonka Truck parked in there also. If the smaller pipe passes the obstruction into the 3" below it may or may not make it to the street sewer.
If not it may have to be found elsewhere in the house drains.
IMO the venting looks OK.

Paul48

It's not his fault, he had to push the rag in, or the Tonka truck wouldn't fit.

Hilly

Was the mystery solved?

LanceT

No, not solved yet.

I pieced together some pvc to give me a temporary vent just after the trap and before it goes into the wall -- the same place one of those mechanical vent things would be installed since someone suggested that would fix it. It did not fix it. Even with a wide open hole where the vent would be, it backed up after a few minutes. So I'm pretty confident it's not the vent.

I also ran a hand rodder into it and got a good bit in (4-6' maybe). I'm not very good and working those things so I don't know if I hit a blockage or another tee where it drops down to the basement. I've been meaning to try it again and measure how much goes in this time, but I have not gotten to it.

My bro-in-law says he has an inspection camera, but he hasn't taken a look yet.

jonny88

Not the vent.I think you got a stoppage.Snake it out real good.If water is not coming out from toilet waste I would imagine you have something in between sink and toilet connection.

JUGHNE

Lack of venting is not the issue. If the vent for that bath group goes straight up thru the roof that is a good spot to enter the drain line under the floor, from the roof. Just so you have a long enough snake and don't let the end out of the drum and have the end fall down the vent. (I know that can happen)

Abracadabra

Why not just rod it from the drain?

JUGHNE

OP stated that he could only get 4-6' and hits something.
The vent looks to be 2". So if the rag/plug is at the base of that wet vent it would be an easy grab from straight above. (If a VTR)

Ironically, I was about to reply this afternoon but got a call from the son trying to auger his kit sink drain line. Could only get 6-8' in the wall. DW ran at night and he is now tearing down the ruined wet basement SR ceiling, cutting PVC open on a sagging 1 1/2" with 10 years of nasty's inside. And he never was fond of plumbing. But 220 miles away so can't help now.

Abracadabra

JUGHNE said:

OP stated that he could only get 4-6' and hits something.
The vent looks to be 2". So if the rag/plug is at the base of that wet vent it would be an easy grab from straight above. (If a VTR)

Ironically, I was about to reply this afternoon but got a call from the son trying to auger his kit sink drain line. Could only get 6-8' in the wall. DW ran at night and he is now tearing down the ruined wet basement SR ceiling, cutting PVC open on a sagging 1 1/2" with 10 years of nasty's inside. And he never was fond of plumbing. But 220 miles away so can't help now.

Run the rod counterclockwise instead of clockwise when encountering the point where you can't push the rod in further. Depending on the head you've got, you may be able to get the rod to sneak past that point. It takes a bit of finesse sometimes.
If all else fails, run the rod with no attachment head at all.. just the rod itself.