Wet Vent - Tub and Shower

[Hiluxsurf]

Hey

So - taking out built in tub to replace with freestanding - need some help on the wet vent as think what is there is weird/wrong. Thanks in advance - learning a lot as an first timer.

Currently there is a 2" 12 ft wet vent running from the shower to the main 3" wet vent - and the tub 1 1/2" drain wye's into that BUT the trap arm drops 5" over 4ft (it's a weird routing with a 90 degree and other turns).
1) I think this drop is too much for code - should be 1/4" per foot - correct?
2) Is it ok for the tub to wye into the shower line, rather than direct into the main 3" wet vent?

Assuming I am correct - I think I should;
- cap off existing wye (it would be difficult to remove as very close to the 3")
- new 1 1/2" drain - with drop of 1/4" per foot
- should this 1 1/2 drain wye into the 3" or the 2" or either

Crappy diagram and photo attached

Also curious if anyone has any ideas why it would have been done like this?!

Appreciate the help

 

[John Gayewski]

The long arm needs a separate vent. You can't have a trap arm that long.

 

[Sponsor]

 

[wwhitney]

Looking at the pencil portion of your diagram as the existing configuration, there are 3 problems with it, of which you've identified half:

1) Each fixture drain needs to be vented before or as it joins another drain. So the tub and shower can't wye together before either one is vented. I.e. with the 3" horizontal line as a wet vent, the tub needs to connect to the 3" line, not the shower trap arm.

2) The fall on a trap arm (from trap to vent connection) is limited to one pipe diameter, to prevent siphoning (the trap weir rule). So certainly the 1-1/2" tub trap arm can't fall 5" before being vented. But also the shower trap arm is too long, as John commented. At exactly 1/4" per foot fall, a 2" trap arm is limited to 2" / (1/4"/foot) = 8' in length.

3) The dry vent for the WC is horizontal at the takeoff, but dry vents needs to come off vertical (up to 45 degrees off plumb) and stay vertical until 6" above the fixture flood rim. [The lav is not shown; if it drains into the pipe on the left you've labeled vent, then the configuration you've drawn is OK, as it is a wet vent, rather than a dry vent.]

Cheers, Wayne

 

[Hiluxsurf]

Thanks John and Wayne - appreciate the rapid replies. Wayne - couple follow up below....to ensure I have understood

On 1) - so I will add a new 3" wye and run a 1 1/2" line to the tub - correct? And ok just to cap the existing/wrong 1/2" wye?

On 2) - that trap arm will be approx 3' long - I will make the drop of the trap arm 1/4" per foot by lowering the p-trap/longer pipe from fixture to p trap (but less than 24")

On 3) - that is probably just my crappy illustration - I actually can't see how the WC is connected to the dry vent - so I'm optimistically assuming that's ok. I can only see the tub/shower connections.

The 12ft shower line was existing and I can't do much about that without a complete remodel - is there any other way they could have done something to make that ok? (I can see the run of the pipe to the shower but not the shower p-trap so can't really see what's going on under the shower). Can't believe it passed code otherwise?

Cheers
Chris

Looking at the pencil portion of your diagram as the existing configuration, there are 3 problems with it, of which you've identified half:

1) Each fixture drain needs to be vented before or as it joins another drain. So the tub and shower can't wye together before either one is vented. I.e. with the 3" horizontal line as a wet vent, the tub needs to connect to the 3" line, not the shower trap arm.

2) The fall on a trap arm (from trap to vent connection) is limited to one pipe diameter, to prevent siphoning (the trap weir rule). So certainly the 1-1/2" tub trap arm can't fall 5" before being vented. But also the shower trap arm is too long, as John commented. At exactly 1/4" per foot fall, a 2" trap arm is limited to 2" / (1/4"/foot) = 8' in length.

3) The dry vent for the WC is horizontal at the takeoff, but dry vents needs to come off vertical (up to 45 degrees off plumb) and stay vertical until 6" above the fixture flood rim. [The lav is not shown; if it drains into the pipe on the left you've labeled vent, then the configuration you've drawn is OK, as it is a wet vent, rather than a dry vent.]

Cheers, Wayne

 

[wwhitney]

1) Cutting in a new 3x3x1-1/2 wye for the tub is a good plan and will wet vent the tub as long as the WC is properly vented. [You'll need (2) shielded rubber couplings, e.g. Fernco 3005-33, assuming the 3" line is fixed at both ends.] As to capping the existing 2x2x1-1/2" wye on the shower, I guess that's OK? It's close enough and you'll have things opened up, I'd consider if it would be not difficult to just remove.

2) The 1-1/2" trap arm sloped can be anything that is at least 1/4" per foot, but no more than 1-1/2" total. So for 3', it could be up to 1/2" per foot.

4) So you can see both ends of the 12' run, the drain in the shower, and the end in your picture near the 3" line. Does it pass under or near any walls? Hopefully it does and there's a vent in that wall. If it does pass through/near a wall, but there's no vent, since you are remodeling, now is the time to add the vent.

An AAV is another option, but it needs to be at least 4"above the shower trap arm (and is maybe 3" high? I've not used them) and in an accessible, ventilated space. So it probably wouldn't fit in the floor framing, but could fit in a knee wall or cabinet or something that doesn't allow a vent to rise all the way to the ceiling.

Cheers, Wayne

 

[Hiluxsurf]

Thank you, Wayne, for making that clear....now, the plot thickens!

I just got a ladder out and went up on the roof - and I can see there is another vent - this must be a dry vent for the shower - so that explains the 12ft arm. So I'm assuming that's all fine? ie it isn't acting (primarily) as a wet vent for the shower, though it is (at the end) for the tub.

In which case two other questions - the last ones!
1). If there is another dry vent at the shower end - should I still cut into the 3" or can I cut into the 2" now?
2). If I have to cut into the 3" - are the shielded rubber couplings better than regular PVC slip couplings (the 3" is PVC)

I cannot tell you how grateful I am for the help here - this has been vexing me since Christmas
C

1) Cutting in a new 3x3x1-1/2 wye for the tub is a good plan and will wet vent the tub as long as the WC is properly vented. [You'll need (2) shielded rubber couplings, e.g. Fernco 3005-33, assuming the 3" line is fixed at both ends.] As to capping the existing 2x2x1-1/2" wye on the shower, I guess that's OK? It's close enough and you'll have things opened up, I'd consider if it would be not difficult to just remove.

2) The 1-1/2" trap arm sloped can be anything that is at least 1/4" per foot, but no more than 1-1/2" total. So for 3', it could be up to 1/2" per foot.

4) So you can see both ends of the 12' run, the drain in the shower, and the end in your picture near the 3" line. Does it pass under or near any walls? Hopefully it does and there's a vent in that wall. If it does pass through/near a wall, but there's no vent, since you are remodeling, now is the time to add the vent.

An AAV is another option, but it needs to be at least 4"above the shower trap arm (and is maybe 3" high? I've not used them) and in an accessible, ventilated space. So it probably wouldn't fit in the floor framing, but could fit in a knee wall or cabinet or something that doesn't allow a vent to rise all the way to the ceiling.

Cheers, Wayne

 

[wwhitney]

1) If the shower is dry vented, then the tub can join the shower drain and be wet vented that way; it doesn't need to go to the 3". But you'll need to fix the trap weir rule violation.

I think the easiest way to do that may be to jog the shower drain to the right in your picture, so that you can put a wye or combo with the entry on the left side and have it fit within the joist bay.

2) PVC slip couplings are much more difficult to use than banded rubber couplings

Cheers, Wayne

 

[Hiluxsurf]

Thank you so much Wayne - I am so grateful to have found the right way forward. Appreciate you taking the time.

The shower drain (though you can't see in the photo) actually runs beneath the joists - and I just looked and think enough clearance for the 1 1/2" to run to the trap under the joist without any additional adjustment.

And appreciate the benefit of your experience on the couplings - saved me some cursing and there I suspect!

Looking at the set up again - I can only assume the original tub drain was in a different position - to where the two 45 degree bends are - which would have been fine. And at some point the drain position changed and that's when an extension to that trap arm was made which violated the trap weir code.

Now I can crack on with the job - and make my wife a happy woman again.

I owe you a cold one.
C

1) If the shower is dry vented, then the tub can join the shower drain and be wet vented that way; it doesn't need to go to the 3". But you'll need to fix the trap weir rule violation.

I think the easiest way to do that may be to jog the shower drain to the right in your picture, so that you can put a wye or combo with the entry on the left side and have it fit within the joist bay.

2) PVC slip couplings are much more difficult to use than banded rubber couplings

Cheers, Wayne