Need advice on small plumbing work

[ladoe00]

Hi all,

I am in the process of building a home theater in my basement and I reached the stage where I need to do some plumbing for my wet bar. I know it is pretty easy, but this will be my first plumbing project, so I'd like to get my plan verified before I start!

Here is a small drawing of what is currently in place (in black) and what I am planning to do (in orange). The gray line is just to show the separation between the 1st floor and the basement. The box with a ? inside is a wall where I'm losing sight of the pipes, so I don't know where they go next.

Key points to note:

1. The bar sink is about 18"-24" away from the drain pipe
2. I would use a 'Y' to tap in an existing vent and route a new vent following the waste pipe down to the bar sink's p-trap
3. All piping is 1 1/2" ABS except the toilet drain which is obviously bigger

My questions:

1. Are there any restrictions about how I tap in an existing vent pipe? Number of maximum connections, etc...
2. Do I really need to connect a vent between my bar sink's p-trap and the waste pipe? Could I just connect the vent to the waste pipe, below the junction of the bar sink's drain?

Thanks for helping

 

[Nailer341]

It is all determined by fixture units.
You are allowed a certain number of fixtures per vent pipe.
What size is the vent pipe? 1.5"

List all items tied into this vent.
Confirm there are 2 sinks, a toilet and your future bar sink.

I hope your vent pipe is larger than the 1.25" specified, or it is technically already over loaded.
In most cases a plumber will run the vents in 2" ABS as this supports so much more fixture units and allows for some changes.

 

[DUNBAR PLUMBING]

You've got the right idea for venting, but keep in mind you shouldn't be reconnecting to the drain side of a fixture on an upper level in that equation, given the way I think you've drawed it out.

You should be accessing a wall and tieing into a vent that's above the highest flood level rim and making sure that there are no floors above, to prevent a wet venting scenario.

 

[ladoe00]

Alright, first thanks for the quick replies guys. It's awesome.

First of all, the vent pipe is 1.5". I have verified and here are the items tied into this vent:

• 1st floor kitchen sink (double) and dishwasher [2.0 DFU]
• 1st floor bathroom sink [1.0 DFU]
• Basement future bar sink [2.0 DFU]

I can't see if that vent is venting anything else since it is inside a wall. If it does, it would be on the 2nd floor, venting my main bathroom sinks.

The 1st floor bathroom sink is draining into the toilet's drain (3" pipe), but it's vent is the same one as the kitchen sink/dishwasher.

The drain of the kitchen sink is "dedicated". It goes from the sink, then inside the basement wall all the way down to my concrete slab.

Now, if I take a look at the drainage DFU, I have:
Kitchen sink/dishwasher [2.0 DFU] + future bar [2.0 DFU] = 4.0 DFU. According to the table, maximum vertical would be 2 DFU. I know the table says that a bar sink is 2.0 DFU, but I don't get why it would be higher than a simple lavatory. I say bar sink because it is part of my "bar", but really I mean a simple small lavatory. So the total would in fact be 3 DFU, one too many...

As for the vent:
Kitchen sink [2.0 DFU] + Bathroom sink [1.0 DFU] + Bar sink [2.0 DFU] = 5 DFU. Assuming it is not venting the 2nd floor batchroom, I would be fine.

So, in summary, is the extra DFU such a big deal considering the fact that this bar sink won't be used every day?
Dunbar Plumbing, you mentioned that I shouldn't be connecting to the drain side of a fixture, but since it is "dedicated" to my kitchen sink, would it be fine? And I'm not so sure I understand what you mean by "highest flood level rim"...

Sorry for the long post! I'm trying to be as clear as possible.

Thanks again.

 

[Nailer341]

Be sure you are looking down the "Private" column for your use.
They give the bar sink a 0 DFU as they expect it wont be used much.

I think you will be fine in tying in the bar sink to the 1.5" vent.

Provided that pipe is no longer than 60', you are allowed 8 DFU.

As stated in a previous post, be sure it is not designed into a "wet vent".
See Dunbar's post.

 

[ladoe00]

Alright, I have verified and as far as I can tell, that vent isn't a wet vent. If it is, it is hidden from me (or is there a trick to verify this?).

As far as DFUs are concerned, I should be below the bar since I would be surprised that this vent is longer than 60'.

I created a 3D desing of my piping so you guys can let me know if I'm clear to go ahead.

Black: actual drain
Grey: actual vent
Blue: future drain
Green: future vent

Thanks again

 

[Otahyoni]

What is a wet vent?

 

[Mr_David]

The green vent should be connected above the flood rim of the black drain.

 

[Mr_David]

when a vent is also a drain from a fixture above the wet vented fixture.
Sometimes a lav sink is connected to the vent from a toilet. The toilet having a wet vent.

 

[Otahyoni]

Oh ok. Thank for clearing that up for me, Kilroy.

 

[ladoe00]

The green vent should be conected above the flood rim of the black drain.

That flood level mystifies me... So you mean the upper end of the green pipe (connecting to the grey pipe in the drawing) should be connected to that grey pipe somewhere higher than the top of the kitchen sink connected to the black drain?

Picture's worth a 1000 words (what I consider the flood level is the large aqua rectangle)

If so, why? To make sure water gets out by the sink instead of propagating in the vent when a problem happen?

 

[phishfood]

Yes, the vent you are showing in green should connect 6" or more above the rim of the kitchen sink, to prevent material from being deposited in the vent and closing it off in the case of a drain stoppage. My guess is that the gray pipe is indeed a wet vent, as your drawing shows it running horizontally below the rim of the sink that it serves.

Also, at the point that the green vent connects to the blue drain arm, it should rise vertically to a point 6" above the rim of the bar sink. If that isn't possible, cut in a wye below the level of the drain arm to the bar sink. Off of the side of the wye, turn an 1/8th bend (45) straight up. Then stack the tee for the drain arm on top of that, and route the vent pipe for the bar sink right beside the existing drain.

 

[ladoe00]

I drew a new sketch with phishfood's recommendation (great idea btw). It just makes more sense this way.

That having been said, I am puzzled by how I will fix this "higher than flood level" constraint. In order to connect the green vent, I would need to open a wall on the first floor of my house and I don't really want to go that route.

I'm finding it hard to believe that if I hire a professional plumber, he will tell me that I need to bring down a wall, redo my drywall, paint, etc... just for a vent. I'm not saying you guys are wrong (absolutely not), but I can only imagine there is a "trick" that plumbers would do in such a situation.
In my basement, about 20 feet away from my bar, I have the rough-in for a bathroom already installed in my concrete slab, so if I would finish that bathroom, I'd need a vent too and I can only imagine that there must be something about venting included in that "rough-in" package that my builder did...

Thoughts?
Thanks again.

 

[phishfood]

The only other real option that meets code (at least the code I work under) is to install an air admittance valve under the bar sink to serve as the vent. In your particular case, I wouldn't, and here is why.

An AAV is basically a one way valve. Air can be drawn in, to supply the trap with air during discharge, but air cannot get out, so the sewer gas can't get into the building. So, an AAV will relieve negative pressure, but not positive pressure. When the existion sink upstairs is discharged, the water flowing down the line will create positive pressure in the drain line behind the bar sink. The only place for this pressure to escape will be through the trap of the bar sink. Also, an AAV is a mechanical device, which can and sometimes does malfunction. If the drain pipe were oversized, which I gather isn't the case here, there wouldn't be any chance of building up pressure, and an AAV might be a good option.

To do the job in a manner that you know is right, and will pass inspection, you need to find a known vent to tie into on the ground floor.