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Thread: 2nd story bathroom addition DWV rough in review

  1. #1
    DIY Junior Member kayakmike's Avatar
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    Default 2nd story bathroom addition DWV rough in review

    First of all, I just want to say this forum is great. I got a lot of input from other posts and examples. Thanks for hosting this site.

    We are looking to add a bathroom to the second story of our house. We are turning a large game room into a new master bedroom suite. House is on a raised foundation, so we can access to the existing 4" main drain through the crawl space. Currently there is some plumbing that may have been for a wet bar or something like that, but it was capped off when we bought the house. Below the new 2nd story bathroom is a jack & jill bathroom, but we are removing one toilet and lavatory sink, and changing the current shower to a tub (in the same location). Because the downstairs bathroom is about 6' wide and standard tubs are 5' long, we have about 1' we can use to help route plumbing downstairs. The 2nd story has exposed beam vaulted ceiling, and all of the plumbing from the J&J bathroom vented horizontal to the 1st story part of the house (that had attic space). The current vent line runs between 2x10 floor joists.
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    For the new upstairs bathroom, we are adding a double vanity on the side wall. I'm thinking of running the wet drain between the floor joists back towards the upstairs shower & toilet drain. The vent we will just take through the roof above the vanities. I think I'm going to have to remove the existing 1st story venting between the floor joists since that will cross where the toilet & shower will need to drain. The other challenge is that both the toilet and shower drains will need to go through a floor joist. Even though they are short runs (toilet ~3', shower ~4'), I can't combine them in the bay the drains are located in and can't combine them until they are in the first bay where I'll add a new vertical stack, so it looks like I'll have to cut a 2+" hole and 3+" hole through the 2nd joist. I'm vertically challenged between floors (2x10 joists).
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    What I've come up with is attached. I can combine the upstairs shower and toilet in a double combination Y-1/8 (3" with reducers for the shower closet bend and vent). I'll have to make a slight joggle to get the vent pipe into the 2x6 wall (a couple of 22.5 or 45 degree bends). If the drain pipes are in the first bay, I can run them down outside of the wall in the space between the tub and original wall. With that I can tie in the wet drain from the upstairs double vanity below/downstream of the shower/toilet. I would also tie in the downstairs tub into this new vertical stack. The existing downstairs 2" vent would have to get rerouted through the 2x6 framed wall into the 2nd story where it will have to get tied into the new 2nd story vent from the shower/toilet.
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    Does this approach seem reasonable? Any other suggestions?

    Thanks,

    Mike

  2. #2
    Moderator & Master Plumber hj's Avatar
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    Your drawing looks good, but you still have to install the piping the same way, and many DIYers find themselves in a bind where they have to take a shortcut and mess up the installation. And, we cannot tell if that is the best installation or not without seeing the actual site.
    Licensed residential and commercial plumber

  3. #3
    DIY Junior Member kayakmike's Avatar
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    Quote Originally Posted by hj View Post
    Your drawing looks good, but you still have to install the piping the same way, and many DIYers find themselves in a bind where they have to take a shortcut and mess up the installation. And, we cannot tell if that is the best installation or not without seeing the actual site.
    Completely understand that without being there in person you can't tell if this is the best approach or not.

    One thing I have found is that it does not appear that there is a 3" double combination Y-1/8 for the toilet & shower entrance to the new stack. Looking at a couple of manufacturer's web sites it appears those come in 2" or 4", but not 3". Can a 3" fixture fitting (not San Tee) be used there instead?

    If that doesn't work, I could do something like this (http://www.terrylove.com/images/sing...double_lav.jpg), but with 3" on one side for the toilet and 2" on the other for the shower. This is more of a challenge with the limited vertical clearance I have to work with.

    Thanks,

    Mike

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    Forum Admin, Expert Plumber Terry's Avatar
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    If that doesn't work, I could do something like this (http://www.terrylove.com/images/sing...double_lav.jpg), but with 3" on one side for the toilet and 2" on the other for the shower. This is more of a challenge with the limited vertical clearance I have to work with.
    It may be code, but a back to back with a toilet doesn't work as well as it used to. A cross or fixture cross with the new toilets will have "skip over".
    When the toilet flushes, the water will skip over to the other trap arm, forcing water out. This wasn't an issue when toilets flushed slowly.

  5. #5
    DIY Junior Member kayakmike's Avatar
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    Default A new approach now that I can see in the walls...

    OK, like HJ said (sort of), the devil is in the details. I started tearing into the downstairs bathroom to see what I have to work with, and saw I wasn't going to be able to execute my original plan. The following photo shows the floor joists looking up from the downstairs bathroom. The 1st bay next to the wall has the existing 2" vent from the downstairs bathroom as well as some electrical. I can't easily get the plumbing over to the center wall without cutting two floor joists more than 1/3 the height right around mid span on the joists, as well as moving the existing vent and electrical.
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    So I thought about it and came up with this approach using a wet vent from the vanities. It's crowded in the 2nd bay right around the shower drain/P-trap, but looks like it will work. It probably could be cleaner if I swapped the toilet and shower locations (wouldn't have all three lines running by the shower P trap), but I've already framed it in and we prefer this layout. All three lines are parallel and at the same elevation.
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    To get it so that the toilet doesn't drain over the shower or vanities, I need to run all three pipes parallel in the floor for a short distance (at the same elevation). I'll have to move the shower drain closer to the toilet so that the closet bend is less than 6' when it connects to the wet vent, but it is doable.
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    Will this approach work?

    If it does, then I can connect the three lines a couple of different ways. The two approaches I was looking at are shown below. Is either way better or preferred? Approach #2 may be easier since it gives me a bit more room when combining the 2" lines into the 3" from the closet bend.
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    DIY Junior Member jasonn1234's Avatar
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    Did this work? I basically had to do the same thing except I had to cross(notch) 4 joists as I wanted to limit the reduction in headroom in the floor below. I was worried about the wet vent being horizontal (multiple posts say it should not be). Did you have any issues?

    I am considering separately venting the shower to avoid a horizontal wet vent as much as possible. Although I needed to vent the toilet(it was 20' from the stack) so I vented mine through the sink wet vent, but tried to keep the sink drain to as much as a vertical angle as possible (though to do in a 10" joists over a 3' run (its more like 15deg off the horizontal instead of the required 45 deg or more

  7. #7
    DIY Junior Member kayakmike's Avatar
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    Yes this worked. Approach #2 worked better since it gave a little bit more wiggle room in stacking up the drain pipes. The devil is in the details. I couldn't put the down drain where it was shown, and had to continue it to the far wall, so I didn't have enough vertical height to get the slope needed. We will be dropping the ceiling 2" in the closet to accommodate the drain slope. Also the shower P trap sticks below the original bay height due to location of the trap relative to the drain pipe slope. Will try and get photos this weekend after we get closer to finish the framing. I got pulled off on a side job and the bathroom work was on hiatus for a few months...

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