Plumbing drain layout for basement back to back bathrooms.

[Jeff H Young]

Pretty typical on homes to have 2x4 16 on center throughout. I've rarely seen 24 centers might get popular with lumber prices up. my brother is building a house 95 000 bucks for lumber and hardware, save 100 studs its what 500 bucksavings? I'm thinking might save 50 studs or less
BTW I'm not seeing a need for 2x6 , I've sure put my share of 3 inch stacks up through 2x4 even the fittings are bigger than a 2 x4 . I'd discuss it with framer

 

[Thekid1]

1) In the last marked up floor plan, both WC drains start off towards the main sump drain at a 90 degree angle. So each one is going to get a wye plus a 45, whether as two separate pieces or as a combo. The drawing is just illustrating that the 45s are have to be at different distances from the sump, so that the drains arrive at different locations, to allow for separate wyes. One of them could use a combo.

2) No opinion, although with the lav drain underground, it is wet venting everything downstream, and your 2" dry vents between the WCs and between the showers are just bonus vents. If you instead run the lav drain separately, the 2" dry vent between the WCs is the dry vent for the upstream WC that wet vents the other WC and the showers.

3) IPC allows two lavs on a 1-1/2" drain, but if you are putting it under the slab it seems to me there's an advantage to making it 2".

4) With only 2" vents and drains in the wall, a 2x4 wall would suffice.

Cheers, Wayne

Ok that's a good plan. Thanks.

I'm having a problem with venting the kitchen sink, since the drain is not underground and will be running behind the wall until it gets to the sump. I was thinking of just venting it on its own to avoid going all the way across the apartment to tie into the bathroom vents. I was thinking to vent it about a foot above grade level. The problem I see with this is the sewer gases coming from the sump and possibly smelling it outside in the yard.

In the photo below(east wall on plans) is my main plumbing right before it goes out to the outside septic tank/cesspool. They have a 3" vent which is about a foot above grade. I see there is a trap right after it but before the septic/cesspool, and I assume this is to prevent smelling it outside. I was actually thinking of tying the bath vents into this 3" line, but now I'm thinking the smell from the sump will come through that 3" vent outside and it will smell. So this leaves me stumped in both the kitchen sink vent and where to vent the baths.

Any ideas?

 

[Sponsor]

 

[Jeff H Young]

We don't use house traps here and no vent can end less than 10 ft off ground or maybe 8 but you have different codes. I'm sure that 2 inch stand pipe unvented wouldn't fly anywhere

 

[wwhitney]

The vertical "vent" just upstream of your whole house trap is actually a fresh air inlet. It should not be used as a fixture vent. Since everything other than the house trap has been replaced with PVC, to my knowledge there is no reason to maintain a house trap. So you could remove the trap and fresh air inlet. But you may want to check with a local expert, I have no experience with whole house traps.

As to venting your kitchen sink, are you in a jurisdiction that uses the IPC/IRC? If so, you could use an AAV if it is too difficult to connect to a vent through the roof.

Cheers, Wayne

 

[Jeff H Young]

I'd like to hear if the house trap is still required there, and if its legal or required to have the vent terminate out the side of a house. I don't know you local conditions or requirements , but My opinion from an out of region plumber is the fresh air vent is stupid and should go up above roofline and windows if any explosive gases were in the sewer it would be easy for them to ignite. but again its an outsiders opinion an open pipe at ground level never made sense to me. but all you locals to east coast can let us know why they do it that in long island.

 

[wwhitney]

I've read about whole house traps, but have no direct experience with them, so here's my limited understanding. The trap obviously isolates the house drains from the sewer. With the air inlet down low near the ground, and the vents through the roof, the idea is that the stack effect ensures that the inlet is at a negative pressure relative to the roof outlets, i.e. stays an inlet. Like a chimney.

But I don't actually know if practice always agrees with that theory, e.g. if perhaps with the wind blowing the wrong way the pressures could change and the fresh air inlet could become an outlet temporarily.

Cheers, Wayne

 

[Jeff H Young]

I'm wondering if any places are still built with them, (house traps) not in 500 year old cities where a new building goes up , but where it has a modern infrastructure as well?

 

[John Gayewski]

Pretty typical on homes to have 2x4 16 on center throughout. I've rarely seen 24 centers might get popular with lumber prices up. my brother is building a house 95 000 bucks for lumber and hardware, save 100 studs its what 500 bucksavings? I'm thinking might save 50 studs or less
BTW I'm not seeing a need for 2x6 , I've sure put my share of 3 inch stacks up through 2x4 even the fittings are bigger than a 2 x4 . I'd discuss it with framer

The 24" centers are going to be getting more and more popular. Not only does it greatly reduce sound transmission (which is the main reason to do it in a back to back bathroom situation), but it also reduces heat loss by a non insignificant and measurable amount. Also less drilling for MEP.

 

[Thekid1]

Thanks for the help guys. I'm not sure of the codes here in Long Island. The house was built in 2000. I made a mistake, that photo of the main house plumbing was in the east wall.

I do have a small 2'x3' closet that has some ductwork going from the attic to the basement. I think I'll run the 2" main vent for the apartment through this closet and eventually tie it into the existing 3" main stack that goes through the roof. I think this should do.....hopefully.

 

[Jeff H Young]

Thanks for the help guys. I'm not sure of the codes here in Long Island. The house was built in 2000. I made a mistake, that photo of the main house plumbing was in the east wall.

I do have a small 2'x3' closet that has some ductwork going from the attic to the basement. I think I'll run the 2" main vent for the apartment through this closet and eventually tie it into the existing 3" main stack that goes through the roof. I think this should do.....hopefully.

thanks for info I had no idea house traps are still used on new homes today or at least into this century.
Just trying to figure out why they would even have a house trap and why its cast iron? never seen one here that I can remember may I did on a 100 year old house or perhaps from the 30s

 

[Thekid1]

The vertical "vent" just upstream of your whole house trap is actually a fresh air inlet. It should not be used as a fixture vent. Since everything other than the house trap has been replaced with PVC, to my knowledge there is no reason to maintain a house trap. So you could remove the trap and fresh air inlet. But you may want to check with a local expert, I have no experience with whole house traps.

As to venting your kitchen sink, are you in a jurisdiction that uses the IPC/IRC? If so, you could use an AAV if it is too difficult to connect to a vent through the roof.

Cheers, Wayne

Hey thanks. I'm piping the vents out now. I'm gonna tie 2" into the existing 3" stack in the attic that goes through the roof. I just want to be clear I'm doing this correctly. For the 2 baths, the laundry and the kitchen sink, I ran 2" pipe for the vents and they all tie into eachother. Then I'm running 2" up to the attic. I don't need to upsize anywhere, correct? 2" all the way for the whole apartment as far as venting is ok, correct? Just curious why the main house has a 3" stack for pretty much the same setup upstairs on the main floor(single story ranch)?

 

[Jeff H Young]

Hey thanks. I'm piping the vents out now. I'm gonna tie 2" into the existing 3" stack in the attic that goes through the roof. I just want to be clear I'm doing this correctly. For the 2 baths, the laundry and the kitchen sink, I ran 2" pipe for the vents and they all tie into eachother. Then I'm running 2" up to the attic. I don't need to upsize anywhere, correct? 2" all the way for the whole apartment as far as venting is ok, correct? Just curious why the main house has a 3" stack for pretty much the same setup upstairs on the main floor(single story ranch)?

its got a 3 inch existing because that's what's there there could be a few different reasons we don't even know what code your on now let alone go back to the year 2000 and check why they ran 3 inch . its not uncommon to require at least a single 3 inch vent out the roof. the 2 inch venting you are running is fine tieing into the 3 inch.

 

[John Gayewski]

Hey thanks. I'm piping the vents out now. I'm gonna tie 2" into the existing 3" stack in the attic that goes through the roof. I just want to be clear I'm doing this correctly. For the 2 baths, the laundry and the kitchen sink, I ran 2" pipe for the vents and they all tie into eachother. Then I'm running 2" up to the attic. I don't need to upsize anywhere, correct? 2" all the way for the whole apartment as far as venting is ok, correct? Just curious why the main house has a 3" stack for pretty much the same setup upstairs on the main floor(single story ranch)?

You can run 120 ft of 2 inch vent piping with 24 fixture units attached.

 

[Jeff H Young]

I'm sure he isn't even close to maxing out but that's right 24 f.u.

 

[John Gayewski]

im sure he isnt even close to maxing out but thats right 24 f.u.

The 120 ft could be close.