My plumber just plumbed out the drain for a new basement sink.

The connector, though is a TEE, not a WYE (behind the stud).

Will waste from the DWV line spill into the sink drain pipe and smell -- or worse, back-up?

(I understand that the P-trap that will go on is supposed to block vapor -- but it looks to me like waste will spill into the sink drain pipe and mix with water in the P-trap. Wrong?)

You have 4"x 1 1/2" Double Sanitary T. One side is sealed. You are using the other end for your sink drain. You will need to install P-trap later on. To answer you question: no, no sewage will spill into the sink nor will you have smell entering living space. In my are of operation, we actually prefer Sanitary Tee as transition from horizontal to vertical and our Code would consider your hook up as Up-to-Code.

Hi Antipode...

Like Milo said, you are all set there. That installation is by code everywhere that I know of. In fact, if he had used a WYE fitting for this application that WOULD be against code.

Just be sure to cap the line as soon as possible. Sewer gasses are coming into your home and that is very unhealthy for you and yours... ;)

Good luck!

MARK

Thanks guys.

I have gotten as far as installing the P-trap. Here's what's happened: the P-trap remained empty for a while, then some sewer line water collected in it. You still think it's A-OK? Will it overflow?

If you have sewer backing up to your new trap - then your 4" drain is most likely obstructed and needs to be snaked. Snake it now, before you cover up.

If you have sewer backing up to your new trap - then your 4" drain is most likely obstructed and needs to be snaked. Snake it now, before you cover up.

Wait, do you mean that the sewage is backing up from below, not dropping in from above?

When water drops from above it won't make a turn towards your sink. It continues downward Water accumulates inside the 4 " pipe and water column will slowly rise until it overflows into the small drain.

Now, you have that new drain open. I am sure you are using plumbing above that room. Do you have any active spills through that PVC pipe ?

Antipode...

If there are fixtures above this new sink connection then your plumber has in fact made a mistake here by not adding a separate VENT.

At a minimum the plumber should add an accessible AAV (air admittance valve... see picture). This is installed at least 6 inches above the trap and as stated, must be accessible through an access door of some kind in case it fails in years to come (allowing sewer gas into home). Be clear that the AAV is not accepted as legal plumbing in most states.

What the plumber is supposed to do here is to run a separate 1.5" vent and connect that into other vents in the basement if possible...

Without a vent the sink trap will get siphoned out when the waste from the fixtures above races past the sink drain and sewer gasses will enter the home... not a good thing... ;)

If no fixtures are above this (I doubt that), then perhaps the drain is clogged as Milo pointed out... but I am thinking the pipe is nearly level, which can't always be helped, and that is making it look like the drain is clogged.

Let us know more here...

MARK

When water drops from above it won't make a turn towards your sink. It continues downward Water accumulates inside the 4 " pipe and water column will slowly rise until it overflows into the small drain.

Now, you have that new drain open. I am sure you are using plumbing above that room. Do you have any active spills through that PVC pipe ?

No, no active spills.

Antipode...

If there are fixtures above this new sink connection then your plumber has in fact made a mistake here by not adding a separate VENT.
Yes, this drain is in the basement, and the kitchen, and 2nd floor bathroom are all above it.


At a minimum the plumber should add an accessible AAV (air admittance valve... see picture).
Nope. Not there.



Without a vent the sink trap will get siphoned out when the waste from the fixtures above races past the sink drain and sewer gasses will enter the home... not a good thing... ;)
Hmmm... so, if I have you right, the P-trap should have the water sitting in it *sucked out* when other fixtures drain. Therefore, after a good shower, the PVC drain P-trap should be empty. Should I look to see if that is happening?

If it looks like water is remaining in the P-trap all the time, am I safe?

(I'm not looking forward to tapping a vent into the line because I now have the walls up and finished.)

Hi again...

This setup absolutely requires that a vent be installed! Even if you don't see it being siphoned today someday down the road when the system is at maximum discharge from above you will see bubbling and movement in the ptrap...

For fun, fill the sinks and the tub and then drain them together... ;) While draining watch the trap... let me know what happens.

Thanks...

MARK

OK, Mark -- I don't know you, but I think you're having a little fun with me...

So we're talking about cutting into the DWV line *above* the sanitary tee and tying in a vent which will connect to the sink drain pipe?

Is this some kind of secret voodoo, or is my plumber an idiot?

Hi Again...

Actually, I was being quite serious... :p

Did you try filling and draining the tub and sink from upstairs yet?? You should...should show what I am talking about here..

I am sorry to hear this is closed in... :confused:

And we are talking about cutting in a vent exactly as I drew it in the picture I posted of the AAV at my last post (post #8)... on the horizontal line.

Plumber certainly did miss... very basic stuff here! If waste comes from above then the individual fixture MUST have a vent installed or, as stated, trap can siphon and sewer gasses will enter home!. Sorry!

Get back to me when you try the tub/sink test... ok?