Basement Bathroom Plumbing Check

[Brooke Stabbert]

Hello,

This is my first post in this forum, but I've really appreciated the information I've found here. Thanks Terry et al!

I am remodeling a 1916 craftsman home in Seattle and expanding the basement bathroom. I tore up the slab in that corner of the house and laid down this plumbing. I was hoping to get feedback confirming it is OK prior to closing everything up. I'm not getting it inspected, but I want it all to be correct and meet code.

The layout will be a sink against the wall on the left (top left in first picture), toilet, and then tub/shower on the right (top right in first pic). The 3" line in the right foreground is for a laundry closet and comes up in the wall between the bathroom and laundry closet. The 3" line in the left foreground also will come up in the wall between the bathroom and laundry closet, but continue up to drain the master bath.

Everything connects into the existing 4" cast iron drain line (top left in first pic, connected via Fernco rubber coupler) that dumps into the primary 4" stack/drain. The upstairs master bath connects into the 4" drain downstream of the backwater valve as it is all above the level of the next upstream manhole cover. The laundry and the downstairs bath all flow through a 3" backwater valve since they are below the level of the next upstream manhole. The backwater access/cleanout extends above the slab and will come out inside the bathroom vanity cabinet. The lav sink is on the left end of the wall, but the drain will have to run horizontally to the right through the studs (non-bearing) to intercept its vertical vent and drain down through the stud wall. It exits the wall with a 45 into a long sweep into the 3" horizontal. It then flows to the backwater valve and the main drain.

The toilet flange is not installed yet, but will come off the straight arm of the 3" Y to the right of the backwater valve. It is wet vented by the 3" line from the lav and the tub/shower. Both the lav and the tub have their own 2" vent as does the laundry. The vent for the tub comes off the trap arm at 45 off vertical to tuck into the stud wall and go up from there.

There will be cleanouts for the for each of the 3" drains running down the laundry wall accessable behind the washer and dryer.

Specific Questions:
1. I can connect the vents to the main stack either in the 1st floor joist bay, which is above the next manhole cover, but below the elevation of the main floor drains (even though the main floow drain connect into the stack below the flood rims of the basement bathroom), or I could connect the vents to the main stack in the attic space above the main floor. The first option would allow the the upstairs drains to flood the downstairs bathroom via the vents if the main drain is blocked. That would not happen if I connected through the attic, but that seems like it might be overkill. Thoughts?

2. I am wet venting the toilet via the vents of the lav and tub. However, wet vents are only allowed within one or two bathroom groups. Since the laundry drain connects to the main drain via this bathoom, but is vented separately, does that invalidate the ability to wet vent the toilet?

Thanks!!!!

 

[Jeff H Young]

Usually a 4 inch drain gets a4 inch cleanout but you reduced to 3 inch not going to pass. Improper venting as well the tub needs a combi. is the open pipe in the ditch a clean out?

 

[Sponsor]

 

[wwhitney]

As you're in Seattle, your plumbing code is the UPC, which restricts horizontal wet venting to a single bathroom group.

1) No, it is not overkill, it is required. A dry vent can only join another dry vent at 6" above the flood rim level of any associated fixtures. So you can't join the downstairs dry vent with the stack where it is a drain, or too low on the first floor.

2) Yes, the laundry drain may not drain through the horizontal wet vent; it needs to join in downstream of the WC (and after the WC is vented via the lavatory wet vent). It also only needs to be a 2" drain, although 3" is fine if you prefer.

Also, your vent takeoff for the bathtub is done with a san-tee on its back, which is not allowed under the UPC. If you want to fully embrace horizontal wet venting, you can omit the tub vent, if you join the 2" lav drain to the tub trap arm before the tub fixture drain offsets downwards (max trap arm fall is one pipe diameter). The lav drain and vent need to be 2" under the UPC (2" minimum wet vent size; 2" vent required for the WC), I can't really tell from the pictures.

Cheers, Wayne

 

[wwhitney]

is the open pipe in the ditch a clean out?

It's the access riser for the backwater valve.

Cheers, Wayne

 

[Brooke Stabbert]

Jeff Young - Thank you for the feedback. The 4" cleanout is about 12" to the left on the main stack, just out of frame of the picture. The open horizontal pipe in the trench is the 3" connection for the water closet, which is not yet connected due to my lack of a 22.5 angle coupling. The vertical arm of the combi for the tub overflow has not been added yet.

Wwhitney - The the main stack is only dry above the basement vent connection in question. There are no drains entering into it above the basement bathroom flood rims. All drains enter the stack below or just above the basement slab. So would it still be required to connect the basement bathroom vents above the level of the upstairs flood rim?

Unfortunately, given my space constraints, I do not see a good way to drain the laundry after the wet vent, but before the backwater valve. While not allowed per code, is there a practical reason that cannot be done performance wise?

In regards to the tub vent, I thought a sani T could be used on its "back" like that for a dry vent. Thanks for the correction. The lav drain and vent are 2", so I can eliminate the tub vent if I connect it to the lav drain/vent before it turns down.

 

[Jeff H Young]

Where is the end of line clean out for the 4 inch? Has to be at the end but you reduced it to 3 , might pass inspection santee on back not good either that's the vent issue on tub. BTW I like how you secured the tailpiece to the tub

 

[wwhitney]

Wwhitney - The the main stack is only dry above the basement vent connection in question.

OK, then connecting there is fine. Is the stack at that point a vent for some other basement fixtures? [Just trying to understand, as if it is not, there's no reason for the stack to exist, since it's not receiving drainage from above.]

Unfortunately, given my space constraints, I do not see a good way to drain the laundry after the wet vent, but before the backwater valve. While not allowed per code, is there a practical reason that cannot be done performance wise?

Good question. Until recently I would have said that the pumped output of the laundry could be high enough velocity to disrupt the wet venting, somehow. But then I learned that in Canada, up to 2 DFUs of unrelated drainage can flow through a horizontal wet vent. So if you move your house to Vancouver, you'd be fine. [The example was in Ontario, so I'm assuming national uniformity in Canadian plumbing codes, which might be a mistake, given the US plumbing code situation.]

Seriously though, I would recommend figuring out a way to comply with the UPC restrictions. Is it important that the upstairs master bath connect downstream of the backwater valve? I understand it doesn't need the protection of the backwater valve, but is it a problem if it connects upstream of the backwater valve? If not, then you could swap the locations of the upstairs master bath wye and the backwater valve (assuming the new location is still under your vanity), and then bring your laundry drain into the adjacent master bath drain.

Another option would be to replace the wye for the WC with a double wye, and bring the laundry in there. There's some concern in some jurisdictions about using double wyes flat, as the branch slope will be only 70% of the straight path slope, but if you keep the latter at 3/8" per foot, the branch slope will be over the minimum 1/4" per foot (UPC).

Lastly, depending on where the closet flange is actually going to be, you may have room for another fitting in there. E.g. if you go with using the lav to wet vent the tub, then the closet bend outlet and the tub p-trap outlet need to be at about the same elevation (differing just by the 1/4" per foot slope required as the drain proceeds from the right to left). If that elevation is higher up like the tub p-trap currently is, you could then bring in the laundry drain at a lower elevation and join them just before the backwater valve, for example. I.e. the first fitting upstream of the backwater valve would be a wye with with the branch inlet upright, receiving the bathroom group fixtures, and laundry drain coming in the straight inlet.

[Edit: if redoing that area to be more compact to add a fitting, using actual wyes with street 45s can be more compact on the straight path than using combos, as in plastic wyes are available street, while combos are not, to my knowledge.]

Cheers, Wayne

 

[Jeff H Young]

Code prohibits backwater valves on the upstairs. when above the upstream manhole. When I used to plumb new homes it was a hassle to run 2 pipes in the trench on certain homes makes it a lot of work. we would have loved throwing a backwater valve on the whole house but illegal. Is this getting inspected?

 

[wwhitney]

code prohibits backwater valves on the upstairs.

Thanks, found it. So scratch that idea.

https://up.codes/viewer/california/ca-plumbing-code-2019/chapter/7/sanitary-drainage#710.1

Cheers, Wayne

 

[Brooke Stabbert]

where is the end of line clean out for the 4 inch? has to be at the end but you reduced it to 3 , might pass inspection santee on back not good either thats the vent issue on tub. BTW I like how you secured the tailpiece to the tub

I was assuming the cleanout on the vertical section of the 3" Laundry line (not installed yet. It will be above the slab in the wall) would be the primary cleanout at the end of the line. That doesn't correct the issue of going from 3" to 4" though.

 

[Brooke Stabbert]

code prohibits backwater valves on the upstairs. when above the upsteram manhole. When I used to plumb new homes it was a hassle to run 2 pipes in the trench on certain homes makes it a lot of work. we would have loved throwing a backwater valve on the whole house but illegal. Is this getting inspected?

Yup, I was just getting ready to post the code ref preventing the upstairs from running through the backwater valve. It has complicated this layout for sure.

This is not getting inspected. I could have run the upstairs through the valve, but then I thought there was much higher risk of upstairs effluent backing up into the downstairs bathroom and coming out the drains down there. I figured it would be better to be non conforming on the laundry sharing the wet vent then to have the upstairs run through the backwater valve.

 

[Brooke Stabbert]

Good question. Until recently I would have said that the pumped output of the laundry could be high enough velocity to disrupt the wet venting, somehow. But then I learned that in Canada, up to 2 DFUs of unrelated drainage can flow through a horizontal wet vent. So if you move your house to Vancouver, you'd be fine. [The example was in Ontario, so I'm assuming national uniformity in Canadian plumbing codes, which might be a mistake, given the US plumbing code situation.]

More than just that, most times when wet venting is allowed, it would allow two full bathrooms to be on one wet vent. So instead of the one laundry connection, I could theoretically have a whole second bathroom attached to that with two sinks, bidet, toilet, tub, and shower, and that would not be considered too much flow for that wet vent.

 

[Brooke Stabbert]

Just had an idea. Get a small 2" backwater valve and put it in the laundry wall, and then let the laundry dump directly into the 3" drain from the upstairs bathroom. The laundry then is still backwater protected, but no longer discharging through the wet vent in the floor. Then I just use the 3" long line that was going to be the laundry drain as the end of line cleanout.

I think that gets me there.

 

[wwhitney]

More than just that, most times when wet venting is allowed, it would allow two full bathrooms to be on one wet vent. So instead of the one laundry connection, I could theoretically have a whole second bathroom attached to that with two sinks, bidet, toilet, tub, and shower, and that would not be considered too much flow for that wet vent.

Right, but none of those are pumped fixtures like a washing machine. And the UPC only allows one bathroom group.

I guess the goal here is to get to compliance with the minimum rework? What is your plan for the bathtub vent takeoff? Depending on how much you rework there, you might be able to bring in the laundry between the WC and backwater valve.

Otherwise, your 2" backwater valve idea seems sound, assuming you have a place for the access. I wonder if a 2" vertical backwater valve would work with a washing machine, or if it would impede flow too much and cause it to back up.

Cheers, Wayne

 

[Brooke Stabbert]

I guess the goal here is to get to compliance with the minimum rework? What is your plan for the bathtub vent takeoff? Depending on how much you rework there, you might be able to bring in the laundry between the WC and backwater valve.

Otherwise, your 2" backwater valve idea seems sound, assuming you have a place for the access. I wonder if a 2" vertical backwater valve would work with a washing machine, or if it would impede flow too much and cause it to back up.

Cheers, Wayne

I'll redo the tub vent today. I think I can make it work with a Y 45 degrees off vertical into a street 45 to run it up into the wall. OK to use a Y off vertical for a dry vent?

For the backwater in the wall, I can place it behind the washer and box it out to provide access to service the valve. It won't be seen, but can be easily accessed by just sliding out the washer. Using a horizontal valve should be no problem.

 

[Brooke Stabbert]

Actually, I just realized the tub vent is inside the footprint of the tub abd I dont have to be so cramped running it up into the wall. So I can use a long sweep like I used for the lav drain. I'll post follow up pics later today.

 

[wwhitney]

I think I can make it work with a Y 45 degrees off vertical into a street 45 to run it up into the wall. OK to use a Y off vertical for a dry vent?

You can use a wye that's rolled 45 degrees off vertical, but then you'd need a 60 to turn vertical.

Of course you can use a combo rolled 45 degrees off vertical with a 45 to go vertical, but that's a bit more total bend, not that it would be a problem.

Cheers, Wayne

 

[Reach4]

Thanks, found it. So scratch that idea.

https://up.codes/viewer/california/ca-plumbing-code-2019/chapter/7/sanitary-drainage#710.1

Cheers, Wayne

I see

710.1 Backflow Protection
Fixtures installed on a floor level that is lower than the next upstream manhole cover of the public, or private sewer shall be protected from backflow of sewage by installing an approved type of backwater valve. Fixtures on such floor level that are not below the next upstream manhole cover shall not be required to be protected by a backwater valve. Fixtures on floor levels above such elevation shall not discharge through the backwater valve. Cleanouts for drains that pass through a backwater valve shall be clearly identified with a permanent label stating "backwater valve downstream."
​

I don't see that as prohibiting a second floor backwater valve, but rather saying that the second floor waste should come in downstream of the lower backwater valves. Of course I may have missed something. I did not read very far.

 

[Brooke Stabbert]

Corrected shower drain and vent. Toilet trap arm and riser installed. Flange just on it as a cap for now.

 

[Jeff H Young]

I was assuming the cleanout on the vertical section of the 3" Laundry line (not installed yet. It will be above the slab in the wall) would be the primary cleanout at the end of the line. That doesn't correct the issue of going from 3" to 4" though.

A few issues Brooke, The clean out size could be an issue , Ive been called out on just about everything over the years and just want to bring to your attention.
As for the Backwater valve I have seen them on whole houses that didnt require one One would think it be ok but not the case

I see

710.1 Backflow Protection
Fixtures installed on a floor level that is lower than the next upstream manhole cover of the public, or private sewer shall be protected from backflow of sewage by installing an approved type of backwater valve. Fixtures on such floor level that are not below the next upstream manhole cover shall not be required to be protected by a backwater valve. Fixtures on floor levels above such elevation shall not discharge through the backwater valve. Cleanouts for drains that pass through a backwater valve shall be clearly identified with a permanent label stating "backwater valve downstream."
​

I don't see that as prohibiting a second floor backwater valve, but rather saying that the second floor waste should come in downstream of the lower backwater valves. Of course I may have missed something. I did not read very far.

Its pretty clear reach 4 this is upc 710.1 just a couple sentances where it says shall not.
I thought of the little 2 inch bw valve too Brooke but didnt mention it. they might have one that can go vertical in the wall like a clean out tee? that would be great