Bathroom remodel : DWV puzzle

Hello,

First, let me say this is a great site with lot of knowledgeable people, it definitely helped me so far !

I'm planning to relocate a bathroom in my house, enlarging it and adding a bathtub and a shower. This is a one storey house, and the basement under the bathroom will never get finished as this is the basement entrance and wood bin. Attic over bathroom isnt finished either.

I drew a couple sketches of what the dwv system could look like, trying to respect the plumbing code (NPC), and would like to know if I'm heading in a wall before going any further... Please help me make this system better and up to code.

Somes remarks first:
- the main stack is around 4 foot from the end of the wall at top left. I need to offset it and will reconnect the main vent in the attic.
- every horizontal run will be sloped at 1/4" per foot.
- the bathtub and shower traps arms lenghts are not indicated, but I will keep them under the max lenght to avoid partial p-trap.
- the bathtub and shower traps are wet vented from lavatorys.
- every fitting on the horizontal run are wye or 45 degree bends.
- the orientation of the tub trap is wrong in the drawing.
- lavs vents will be in an exterior wall, but the drains will go throught the floor. the vent will take of a sanitary tee and will offset at no more than 45 degrees to reach the wall. (is this ok?)
- i want to avoid piercing joists as much as possible, but the tub trap is in the way of the exterior door if below joists, and I read many times than the closer the trap to the fixture, the better it will be.
- Co on the drawing is a Cleanout.
- The dimensions and proportions of the room are corrects.

Here is the drawing :


And here is the conceptual plan :



If some details are missing I will provide them promptly.

This job will be inspected so I definitely want to get it right.

Thanks a lot for your time !

If it is a 2" drain, it may not be large enough, you would have to check with your plumbing department. In any case, it is NOT how I would do it, because it makes a drain which would be very hard to "snake" if it gets clogged and what good is a cleanout when it is between the floor and ceiling?

Hello,

Thanks hj for your answer. I've been reading your posts for quite some time, and I know than if I follow your advices, I will get a good design.

The cleanouts will be accessibles between joists as the room below the bathroom will never get a finished ceiling, is it possible to "snake" in this situation?

I did rework my first drawing to try to get more direct paths to main stack. The bathtub is now vented individually by a dry vent, and it drain is connected directly to main stack. The 2" drain now only serve 2 lavatorys and a shower, wich I think is ok if I understand the dfu logic in the UPC : 2 dfu (shower) + 2 dfu (lavs) = 4 dfu, and a 2" horizontal drain can serve up to 8 dfu, is this correct?

I would like to get a straight line from right lavatory to main, but that would get me a shower trap arm longer than 5 feets, wich is not permitted. Is it better to wet vent the shower from the lavatory to get it to drain in direction of the main stack, or would it be better to reach the right wall to dry vent there and U-turn the drain to main?

Here is the new drawing :
(Circles are vertical vents)



Thanks again for your help !

Personally, I cannot remember EVER using 1 1/2" for a horizontal drain under a floor. We always used 2" miminmum. 1 1/2" was ONLY for waste arms and vents.

2" minimum for drains then :



Is this ok that way? If not, how could I improve the layout?

Thanks !

The sink on the left hand side needs to be wet vented, as to clean outs you do not need them by code but if you want some the install them between the ty coming out of the wall for the sinks and the two 45 at the bottom.

Thanks Bill for the answer. I will add 2 cleanouts, one for each sink, between the santee and the 45 bend. Thoses will be accessibles inside the sink cabinet.

Living here up north, you know how cold ours winters can be, so you might be well placed to answer one of my questions : can you put vents in an exterior wall? The sinks are againsts an exterior wall : the drains would go throught the floor in the cabinet, and the vents would take of sanitary tees, offset at 45 degrees to reach the wall and then go up in the insulation. Is this an acceptable solution? I would like to avoid building a "fake" wall over the exterior wall to put vents...

In my last drawing, the left hand side sink has it own dry vent connected to the right sink vent 6" above flood rim. I tought of joining the vents in the wall and the drains below floor because the drains needs to be inside the cabinet (to avoid frost), and the cabinet is 2 columns of "U-shaped" drawers. I firstly tought that both lavs trap arms should reach a double fixture cross in the center of the cabinet and wet vent from there, but the "U-shaped" drawers are in the way... If you say than the left lav cannot be vented the way I drew it, I will ask the cabinet maker to leave a space between the drawers and the end of the cabinet to accomodate the double fixture cross. Is this the better solution?

Thanks again, I appreciate !

quote; The sink on the left hand side needs to be wet vented,

And, how would he do that since there is no "higher" fixture to provide the "wet vent". Vents AND drains can go in the exterior wall because they can only freeze if there is a continual small drip from the faucet, and even then conditions have to be "perfect" for it to happen. The general rule, when not specified in your code is a cleanout is required if the distance to the connection with the main drain is over 6'.