Adding Bathroom Above Crawl Space

[HereInOhio]

I'm adding a bathroom above the crawl space and trying to prevent hacking the load bearing wall to run the plumbing. Can I ran the tub and the sink drain straight down into the crawl space where I would have a P-trap for each fixture just below the floor joist. From there I would bring both drains together (~3' each) to a double san-tee and only run one vent pipe up through a joist bay in wall. Since the drain pipe will run under the floor joist in the crawl space I have plenty of room.

I recently asked a similar question about a double vanity I have and was told this is an option but should add a cleanout above this. I could add it right above the double san-tee which will still be in the crawl space or I can add it in the attic at the top of the vent.

Would this be acceptable or is it a bad idea?


Sorry I'm not the most artistic but I tried to sketch out the situation below (green is the drain pipe, blue is the vent, dotted lines are the wall studs, also showing the floor, joist, and crawl space)...

 

[Terry]

Venting for the lav is at the top of the trap arm, not below the floor.

 

[Sponsor]

 

[HereInOhio]

If I laid it out like this I could get away with only drilling one hole through one stud which shouldn't be a problem. This would allow the tub to be vented and the vanity to have a normal vent and P-trap. I'm assuming this is a better option?

 

[HereInOhio]

Venting for the lav is at the top of the trap arm, not below the floor.

Ok makes sense. I didn't know if you could have the lav trap below the floor since there's access to it. I think the second option I posted will probably be a better way. Thanks!

 

[Terry]

Maybe like this, excuse the horrible painting.
Though the one above on post #3 would work too.
Venting for the lav is above the floor, not below.

 

[HereInOhio]

Maybe like this, excuse the horrible painting.
Though the one above on post #3 would work too.
Venting for the lav is above the floor, not below.

Even better! I'm assuming the 2" section between the tub drain and the lav drain would just be considered a wet vent? For the tub 1 1/2" drain is fine? I thought I read that you really want a 2" drain for a tub. It wouldn't hurt putting a 2" trap and drain to the tub would it?

Thanks again!

 

[Terry]

Tub drains tend to be 1.5" so most of the time, I'm running a 1.5" trap and trap after after I pull off the venting. After the vent it's always 2".
And a 2" trap also works if you want to do that.

What I'm showing in red is a wet vent with the lav over the tub.

 

[HereInOhio]

Tub drains tend to be 1.5" so most of the time, I'm running a 1.5" trap and trap after after I pull off the venting. After the vent it's always 2".
And a 2" trap also works if you want to do that.

What I'm showing in red is a wet vent with the lav over the tub.

Fair enough, 1.5" it is. What about for your kitchen sink drain, do you run 1.5" or 2"?

 

[Terry]

Kitchen sink is 2" with a 2" cleanout.
The trap and the vent can be 1.5"

 

[wwhitney]

If you want to avoid drilling any studs, you could use Terry's layout and move the vertical stack over to the stud bay behind the lavatory. The tub trap arm is limited in length, under the IPC in force in Ohio, to 6' if 1.5", or 8' if 2". (Either is fine). The trap arm is also limited to one pipe diameter total fall, so those length maximums are only achievable with a perfect 1/4" per foot slope.

Cheers, Wayne

 

[HereInOhio]

Thanks guys! I think I have it from here. These two projects should keep me busy for awhile. I have a basement that I am adding an ejector pump and bathroom to so that will be a topic for another day, mainly regarding the venting of it.

 

[wwhitney]

BTW, if I recall, where the vent runs through the top plate of the load bearing wall, if the hole size exceed 50% of the width of the plate, then a metal reinforcing strap is required. The details are in the IRC.

Cheers, Wayne

 

[HereInOhio]

Kitchen sink is 2" with a 2" cleanout.
The trap and the vent can be 1.5"

Sorry for 20 questions'ing you. For the kitchen sink 2" cleanout would you prefer that to be located in the sink base or down in the basement? I will have access to both and planning a long sweep 90 once in the basement to go to the crawl space and connect to what I was asking about above. I could just do a long sweep tee with a cleanout in the basement if that would be a better option. If in the sink base is better do you locate it above or under the stub out?

 

[Reach4]

If I laid it out like this I could get away with only drilling one hole through one stud which shouldn't be a problem. This would allow the tub to be vented and the vanity to have a normal vent and P-trap.

If you want to be able to recess the medicine cabinet into the stud space, there are ways to make the vent go around the medicine cabinet.

 

[HereInOhio]

Ok I was able to layout everything else in this house to show the location of it. You helped me figure out the bathroom wall to the left. I'm looking for a few pointers of how to tie the stuff together. Thanks in advance!

1.) For the toilet I will use 3" PVC and have a 2" vent extending up the wall behind it to the blue line which leads to the main vent (yellow circle to the right). I'm wondering if I should have the vent tie in behind the closet flange or in front of it? I attached a picture to help show what I'm explaining. Also the toilet drain is running below joists in a crawl space. It does have a washer and dryer down there so its more of a crawl space/basement. Should I run it perpendicular to the joist and use a 90 to get over to the main sewage pipe (green hole) or should I just have it go directly to the green hole?

2.) At the bottom of the picture is the kitchen sink in a corner cabinet with a wall behind it. I will go up the wall to tie into the vent. I will drop the drain straight down the wall (yellow circle at the bottom). Would I need a cleanout here? Unfortunately duct work and the front of the furnace (purple) is right behind it in the basement so I can run back to the main sewage drain. I will have to bend to the left and shoot back which will lead me behind the piping for the vanity and tub (yellow circle on the left) which I was asking about above. The kitchen will be in 2" and so will the tub/vanity at this point. Can I just have the kitchen meet up with the vanity and tub drain and finally into the main sewage? Would I want this to tie into the main stack above or below where the 3" toilet ties in? Or would I want it to tie into the toilet vertical pipe?

3.) Lastly the green circle is the main sewage pipe in the basement floor. The blue hole is the 3" main vent through the roof. All of the piping is out of the house currently and there's just a hole in the roof. I figured just use it and tie the vents all in to it. Is there any special way this should be done? Is it neater to run it along the joist and 90 over or is it better to just go directly to the vent? If there is a strong reason to patch the hole in the roof and install a different vent I can but trying to avoid it.

 

[wwhitney]

1) First picture not allowed. And the IPC doesn't have a provision for the vent to go horizontal below the flood rim level of the fixture, either, so the second picture is problematic How tall are the joists and which way do they run in your picture?

2) No comment on the cleanout question, not something I've studied. Drains that have been vented can combine in any order you like.

As for the questions of "run the pipes parallel or perpendicular to the joists" vs "run the pipes the straightest way," the latter does have an advantage of reducing elbows. But I might be inclined to compromise and go with "run the pipes parallel, perpendicular, or at a 45 to the joists" to look a little neater and avoid 90s.

Cheers, Wayne

 

[HereInOhio]

1) First picture not allowed. And the IPC doesn't have a provision for the vent to go horizontal below the flood rim level of the fixture, either, so the second picture is problematic How tall are the joists and which way do they run in your picture?

2) No comment on the cleanout question, not something I've studied. Drains that have been vented can combine in any order you like.

As for the questions of "run the pipes parallel or perpendicular to the joists" vs "run the pipes the straightest way," the latter does have an advantage of reducing elbows. But I might be inclined to compromise and go with "run the pipes parallel, perpendicular, or at a 45 to the joists" to look a little neater and avoid 90s.

Cheers, Wayne

I was delayed a bit. I'm actually helping a friend out with this and he was just going to hire a plumber to come out but keeps getting the run around. I went over there again and the floor joist are 2x8" and would run vertically in the picture above so the toilet would run across (under?) the joist and couldn't go into a joist bay. I believe the house is built when the dimensions were actually that size and not 1/2" smaller.

The crawlspace is tall enough to walk in but too short to consider a basement. It does have the washer and dryer down there but where the plumbing is it is fine for the plumbing to go below the joist as well. Looking closer at it the kitchen sink can run straight to where the toilet is and not loop around. Originally I thought the HVAC ducts would prevent this but there is just enough clearance above them. I'm thinking the kitchen sink that is vented could wet vent the toilet correct?

Red is drain pipe and blue is vent.

 

[wwhitney]

Did not fully reacquaint myself with this thread, but I see a question:

I'm thinking the kitchen sink that is vented could wet vent the toilet correct?

No, wet venting is limited to bathroom groups. The kitchen sink can't participate.

But if the two orange rectangles near the WC are the tub and the vanity, and if the plumbing for them is like the drawing from Terry (post 5), you do have the option to just run the WC drain over to the vertical 2" below the bathtub, and tie in there (causing the downstream drain to all be 3"). That allows the lav to vertically wet vent both the tub and the WC. And the WC fixture drain does not have a length limitation in the IPC, so the distance from the WC to that 2" stack is not an issue.

Cheers, Wayne

 

[HereInOhio]

Did not fully reacquaint myself with this thread, but I see a question:


No, wet venting is limited to bathroom groups. The kitchen sink can't participate.

But if the two orange rectangles near the WC are the tub and the vanity, and if the plumbing for them is like the drawing from Terry (post 5), you do have the option to just run the WC drain over to the vertical 2" below the bathtub, and tie in there (causing the downstream drain to all be 3"). That allows the lav to vertically wet vent both the tub and the WC. And the WC fixture drain does not have a length limitation in the IPC, so the distance from the WC to that 2" stack is not an issue.

Cheers, Wayne

Ok perfect, that is the question I had. Yes, the two rectangles are the tub and vanity. Although you can not have the kitchen wet vent the WC would I still be able to connect it into the WC drain as I have in the picture above or would I need to separate the drains and tie into the main stack at different heights? If the latter does it matter if the WC connects to the main stack above or below the kitchen drain?

The vent from Terry's post 5 would be directly behind the vanity. I'm assuming I would either want to run the WC directly below the lav/vent -OR- would want the vertical vent adirectly above where the WC joins (like the pic below) opposed to having WC run to where the tub drain is and 90 over before connecting to the lav/vent? Maybe I'm wrong but it seems like the WC swooshing past the tub would clear the trap if that was the layout.

 

[wwhitney]

In Terry's diagram, the vertical drain/vent can be anywhere you want left-right. You just have to be sure the lav and tub trap arms meet the limits (1.5" trap arm -- 6' maximum length, 1.5" maximum fall before vent).

As to the order on the vertical vent/drain, from top down, the order has to be lav, then tub, then WC, then kitchen sink (anywhere downstream). The kitchen sink drain obviously has to be vented at the kitchen sink trap arm elevation, well before it joins into the bathroom drains.

Cheers, Wayne