How badly against code is this?

[megamax]

My county follows IPC for plumbing code. My basement currently has a decent amount of concrete busted up for a separate project so I'm taking advantage of that to run plumbing for an eventual bathroom down there. I'm worried what I've done isn't to code, and would love a second opinion.

In the photo on the top left you can see the old 3" PVC line which is coming from an addition built on the house and has a toilet/shower/sink, a washing machine, and a dishwasher upstream. To the right of that is the 4" cast iron main stack (that "support" was just a paranoia addition, it's supported with the proper gear further up) and it has a toilet/sink/bath upstream. I took this photo before finishing, but the cast iron main stack was adapted to the 4" horizontal PVC by using a 4" wye + 45 elbow, which provides a cleanout. A shielded fernco is used to adapt the PVC to the cast iron leaving the house.

The old addition PVC line ran through the headspace of the basement, so I'm burying the line as seen by the "New Addition Line" on the bottom left of the photo. This new addition line will have a Wye installed for a bathroom sink for the basement, which will have it's own dry vent (tying into the main stack above all fixtures).

I've added plumbing for a shower and toilet, but my main concern is the venting for that shower. From the cast iron main stack to the basement wall on the right will be a wall separating the toilet from the shower, so I plumbed in a dry vent there for the shower, but in it's configuration, my understanding is that it technically becomes a wet vent due to the upstream fixtures and the fact that it's ~8" upstream of the shower tie-in. Even worse, I believe that makes it a "soiled" wet vent, which as I understand it, isn't allowed. It's currently capped, but will also eventually tie in to the main stack above all the other fixtures.

 

[hj]

The "dry vent" looks good, but that is all it does. It performs no USEFUL function other than looking good. The shower and toilet are both unvented.

 

[Sponsor]

 

[megamax]

The "dry vent" looks good, but that is all it does. It performs no USEFUL function other than looking good. The shower and toilet are both unvented.

Shoot, okay. I appreciate the candid response. Do you see any way I could reasonably make this configuration work? The toilet and shower straddling the main line seems like a challenge.

Also, I thought I had mentioned it in the original post, but it looks like I totally neglected to mention; the "dry vent" in the picture is only temporarily capped like that. The original idea was to tie it into the main stack above any other fixture.

 

[Gagecalman]

I'm not a plumber.
You might want to check and see if you need to install a sewer backflow device. My friend added a basement bath and the city required it.

​

 

[megamax]

I'm not a plumber.
You might want to check and see if you need to install a sewer backflow device. My friend added a basement bath and the city required it.

​

Thank you for the reply! The system thankfully already has one just outside the house. Although I am looking at options for the shower drain, as any internal clog (especially at the backflow preventer) will hit the shower drain first.

 

[wwhitney]

Shoot, okay. I appreciate the candid response. Do you see any way I could reasonably make this configuration work? The toilet and shower straddling the main line seems like a challenge.

On that point, is the building drain (main line) deep enough that you could put all of the basement fixture plumbing at a higher elevation that can cross over the building drain? I think you'd need an extra 5 or 6 inches of height--looks like that might interfere with the slab.

Otherwise, you could add separate dry vents to the WC before it hits the building drain, as well as to the shower. Although for the shower, since you said the "new addition" line has a dry vented basement lav on it (presumably just out of frame to the left), you could instead keep that lav drain separate from the "new addition" line (just running along side it, parallel). Then you can hit the shower trap arm with the lav drain, and that would wet vent the shower, in lieu of a separate dry vent for the shower.

When you say the dry vent will be reconnected to the stack above all the fixtures, just to double check that means all the fixtures in the house. So you'll be carrying a dry vent up a story or two. [The IPC would allow AAVs instead.]

Lastly, on that Fernco in your picture, it's the correct type to use above ground, but not buried. For direct burial you want the 4" long type, which is available unshielded with 2 clamps, or shielded with 4 clamps. Not sure when it's appropriate to use the shielded vs unshielded.

Oh, and plus one on checking on the need for a backflow device. The question is whether if the sewer in the street backed up, is there a manhole that would overflow before the backup came into your house.

Cheers, Wayne

 

[megamax]

On that point, is the building drain (main line) deep enough that you could put all of the basement fixture plumbing at a higher elevation that can cross over the building drain? I think you'd need an extra 5 or 6 inches of height--looks like that might interfere with the slab.

Otherwise, you could add separate dry vents to the WC before it hits the building drain, as well as to the shower. Although for the shower, since you said the "new addition" line has a dry vented basement lav on it (presumably just out of frame to the left), you could instead keep that lav drain separate from the "new addition" line (just running along side it, parallel). Then you can hit the shower trap arm with the lav drain, and that would wet vent the shower, in lieu of a separate dry vent for the shower.

Thank you for the response Wayne! The "new addition" line unfortunately also has a WC on it. I could maybe spare 5-6 inches in height, but unfortunately I think that wye to transition between the lower and upper line will push the WC far enough left to be awkwardly placed (the idea was the have the back of the WC close to the finished wall that will be installed on the right). It seems like the configuration I was aiming for with the WC is going to be hard to accomplish.

When you say the dry vent will be reconnected to the stack above all the fixtures, just to double check that means all the fixtures in the house. So you'll be carrying a dry vent up a story or two. [The IPC would allow AAVs instead.]

Yeah above all other fixtures; the house is a single story + basement and all of the main floor fixtures tie into the main stack in the basement.

Lastly, on that Fernco in your picture, it's the correct type to use above ground, but not buried. For direct burial you want the 4" long type, which is available unshielded with 2 clamps, or shielded with 4 clamps. Not sure when it's appropriate to use the shielded vs unshielded.

Darn, ok I'll make a run to the plumbing store and grab the 4" long type. Thank you.

Oh, and plus one on checking on the need for a backflow device. The question is whether if the sewer in the street backed up, is there a manhole that would overflow before the backup came into your house.

Cheers, Wayne

Thankfully there's a backflow device just outside the house, between my drain and the city sewer. I appreciate the explanation regarding the manhole!

 

[Reach4]

The cool deal is to have the upstairs drainage to connect downstream of the backwater valve, and have the backwater valve just serve the basement loads. I understand that would be a major re-do of stuff, so is not easily retrofit. Also, normally-open backwater valves are better than the hanging flapper. Those flappers routinely get held open by debris.

 

[megamax]

The cool deal is to have the upstairs drainage to connect downstream of the backwater valve, and have the backwater valve just serve the basement loads. I understand that would be a major re-do of stuff, so is not easily retrofit. Also, normally-open backwater valves are better than the hanging flapper. Those flappers routinely get held open by debris.

Ahh that's an awesome idea. Thank you for the reply. Ok it sounds like I need to re-think this entire design. I want to do it by code and proactively avoid any plumbing issues. Preferably BEFORE it's buried under concrete, haha.

 

[wwhitney]

Ahh that's an awesome idea.

FWIW, in new construction it's also mandatory. As an existing building, you are allowed to have everything flow through the backwater valve. As the code says, you need to determine " the elevation of the manhole cover of the next upstream manhole in the public sewer."

Chapter 7: Sanitary Drainage, Plumbing Code 2018 of Oklahoma | UpCodes

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Cheers, Wayne

 

[Tuttles Revenge]

Here is a diagram that shows how to determine whether a backwater valve is needed. ONLY the fixtures on the Floor levels below that upstream manhole can pass through it.. Fixtures on Floor levels above that elevation Shall not pass through the BWV.

 

[Jeff H Young]

I was wondering about wet venting the shower to a lav but I dont even see a lav for that bathroom in basement. I see a shower and a w/c and then a line going to New addition so perhaps there is a lav to complete the bathroom plus a new addition ?

 

[megamax]

FWIW, in new construction it's also mandatory. As an existing building, you are allowed to have everything flow through the backwater valve. As the code says, you need to determine " the elevation of the manhole cover of the next upstream manhole in the public sewer."

Cheers, Wayne

Here is a diagram that shows how to determine whether a backwater valve is needed. ONLY the fixtures on the Floor levels below that upstream manhole can pass through it.. Fixtures on Floor levels above that elevation Shall not pass through the BWV.

Thank you guys for the replies! So already existing is a backflow preventer outside the house, between me and the main sewer line. But I am fond of the idea of having a backflow preventer between the basement plumbing and the rest of the house.

I also have been really firing from the hip on this project, out of stress from trying to get it completed as fast as possible. The philosophy was: get plumbing in the ground before the concrete is poured (any day now) and figure out the rest later. But I want to sincerely thank you all for your help and replies, as you've not only given me some great advice, but have also motivated me to sit down and properly plan the bathroom.

I initially had planned on the WC being back against the far south wall, but there's just not enough room to make that happen. I was originally going to extend the wall separator between the WC and the shower just up to the main stack, but now I've designed it to extend ~2 ft past the main stack, which allows me to move the WC further North, and use the remaining gap as a closet.

I've attached freshly drawn diagrams below (each square = 6", the elevation view is not very accurate), but my plan is to use a 4"x4"x3" wye on it's back to elevate the basement bathroom plumbing above the main line. From there I'll install a 45, followed by a backflow device to protect the basement plumbing. After the backflow device, I have a 3" long sweep combo going East for the WC, and a 3"x3"x2" long sweep combo going West for the shower. The three inch line will imitate the main 4" stack and end in a 3" 45 + wye combo to provide a clean out. After that, I may reduce to 2" for a dry vent, which will connect to the main stack above all other fixtures.

For the partition wall, I'll build removable access panels for the cleanouts and the backflow device. Do you guys think this will pass code? Thanks again for all your help; this has really set my head straight.

 

[megamax]

I was wondering about wet venting the shower to a lav but I dont even see a lav for that bathroom in basement. I see a shower and a w/c and then a line going to New addition so perhaps there is a lav to complete the bathroom plus a new addition ?

My apologies, I should have better explained the "Addition" line. That 3" line comes from an addition that was built onto the house in 1992. It has a shower, wc, lav, and laundry on it. The issue was that it ran through the headspace of what I would like to be finished space, so instead, I'm dropping it below grade in the utility room, and running it horizontally to connect to the main line. I'm planning on using a 3"x3"x2" wye to connect the basement lav to the underground portion of that 3" "Addition" line. That lav I believe I can easily dry vent.

 

[wwhitney]

I'm planning on using a 3"x3"x2" wye to connect the basement lav to the underground portion of that 3" "Addition" line. That lav I believe I can easily dry vent.

Haven't reviewed your drawings yet, but just a quick comment that the dry vented basement lav's drain is useful for wet venting other basement fixtures, if you keep it separate. Once you combine it with the branch drain from the upstairs, it loses the ability to be used in that way.

Cheers, Wayne

 

[wwhitney]

Two problems with your drawings, with the same solution:

- The basement lav is not behind the backwater valve
- On the upper 3" horizontal line, the portion upstream of the combo where the shower comes in is a horizontal dry vent below the slab, which is prohibited.

So:

- Change the elevation of the basement lav drain to be at the elevation of the other basement fixture drains. [IPC would allow the basement lav drain to be 1-1/2", but 2" is probably preferred by most.]
- Join the basement lav drain to the shower trap arm that is running left-right on the page in your plan view. This wet vents the shower and the WC.
- Eliminate the dry vent that is just upstream of the shower on the 3" line; you can keep the 3" line extension as a cleanout.

Some notes:

- For the connection of the 3" basement branch to the 4" building drain, a 4x4x3 wye plus a 3" street 45 in an upright wye configuration (the configuration where the inlets are parallel) puts those inlets 6.5" apart. Your 4x4x3 wye doesn't have to be completely upright, you can roll it to lower the basement branch while moving it left or right of the building drain. You just need enough elevation to keep the drains from touching each other anywhere, maybe 1/2" to 1" would be enough.

- Those with underslab DWV experience would be better able to comment on this, but it strikes me that having two parallel drains run one directly above the other would be annoying to initially install and annoying to service in the future. Looks like you could offset or bend the 3" basement branch to either side. In the "upright wye", you can use a regular 45 with the wye to get any c-t-c spacing of 7.5" or more.

Cheers, Wayne

 

[megamax]

Two problems with your drawings, with the same solution:

- The basement lav is not behind the backwater valve
- On the upper 3" horizontal line, the portion upstream of the combo where the shower comes in is a horizontal dry vent below the slab, which is prohibited.

So:

- Change the elevation of the basement lav drain to be at the elevation of the other basement fixture drains. [IPC would allow the basement lav drain to be 1-1/2", but 2" is probably preferred by most.]
- Join the basement lav drain to the shower trap arm that is running left-right on the page in your plan view. This wet vents the shower and the WC.
- Eliminate the dry vent that is just upstream of the shower on the 3" line; you can keep the 3" line extension as a cleanout.

Some notes:

- For the connection of the 3" basement branch to the 4" building drain, a 4x4x3 wye plus a 3" street 45 in an upright wye configuration (the configuration where the inlets are parallel) puts those inlets 6.5" apart. Your 4x4x3 wye doesn't have to be completely upright, you can roll it to lower the basement branch while moving it left or right of the building drain. You just need enough elevation to keep the drains from touching each other anywhere, maybe 1/2" to 1" would be enough.

- Those with underslab DWV experience would be better able to comment on this, but it strikes me that having two parallel drains run one directly above the other would be annoying to initially install and annoying to service in the future. Looks like you could offset or bend the 3" basement branch to either side. In the "upright wye", you can use a regular 45 with the wye to get any c-t-c spacing of 7.5" or more.

Cheers, Wayne

Wayne! Thank you so much for the awesome comment, I completely forgot about the horizontal dry vent. (On that note, during all of this research I've been perplexed as to why a horizontal wet vent is allowed, but a horizontal dry vent isn't).

I made a quick sketch of the revised plan as I understood it. The only question I had, was that this configuration would put the wet vent distance to the shower at 9'. For 2" is the maximum horizontal distance 8'? But if that is the case, I can move the shower drain further North to reduce that distance, as the shower drain location is variable.

Thanks again for the excellent advice!

 

[wwhitney]

(On that note, during all of this research I've been perplexed as to why a horizontal wet vent is allowed, but a horizontal dry vent isn't).

Dry vent sees no flow during regular use, debris could accumulate and block it. Wet vent sees flow that should clear it.

The only question I had, was that this configuration would put the wet vent distance to the shower at 9'. For 2" is the maximum horizontal distance 8'?

The regulated distance is from the shower trap to the wye where the lav drain (the wet vent) joins the shower drain. That is the shower trap arm. The length of the wet vent upstream of that wye is unregulated.

Cheers, Wayne

 

[megamax]

Dry vent sees no flow during regular use, debris could accumulate and block it. Wet vent sees flow that should clear it.


The regulated distance is from the shower trap to the wye where the lav drain (the wet vent) joins the shower drain. That is the shower trap arm. The length of the wet vent upstream of that wye is unregulated.

Cheers, Wayne

Ahhh! Both comments make perfect sense to me. Thanks again Wayne, and everyone else who commented. You guys are lifesavers!

 

[Reach4]

Read up on this one: http://backwatervalve.com/products/fullport-backwater-valve.html
I have not used it.