Help laying out plumbing under slab

[MeMol]

Hi everyone. We are owner-builders doing an almost 100% DIY ICF build, in FL. So IPC. Long story short, we have no choice but to DIY the plumbing. We are comfortable with most of the plumbing *above* the slab, but this is our first time actually roughing in plumbing under a slab. We are struggling with how we should lay it out. Mostly my concerns are around venting! The toilet is upstream of the shower, bathtub, and sinks in both bathrooms. Can y'all help me lay this out so it will be appropriately vented? I assume wet venting for bathroom groups, but in reading the codes I am just flat out confused as to whether or not the sink vents will be adequate venting for the whole bathroom and specifically the upstream toilets. The red arrow indicates where the line has to leave the house due to pre-existing septic tank location.

I appreciate any help!

 

[Reach4]

https://www.iccsafe.org/wp-content/uploads/20-18927_GR_2021_Plumbing_Venting_Brochure.pdf page 12 at the bottom has a nice drawing of what you can do with IPC wet venting. Wet venting can include up to 2 bathrooms in the same group. I expect you would have 2 groups. Note where it says 2 inch and 3 inch pipe. Non-bath drainage must join after the wet vent group(s).

 

[Sponsor]

 

[MeMol]

https://www.iccsafe.org/wp-content/uploads/20-18927_GR_2021_Plumbing_Venting_Brochure.pdf page 12 at the bottom has a nice drawing of what you can do with IPC wet venting. Wet venting can include up to 2 bathrooms in the same group. I expect you would have 2 groups. Note where it says 2 inch and 3 inch pipe. Non-bath drainage must join after the wet vent group(s).

Thank you, that is very helpful!!!

 

[Jeff H Young]

might not be able to horrizontal wet vent much of it remember the kitchen , and laundry must connect to mainline down stream of any fixtures being wet vented in horrizontal fasion.
I looked at your drawing having a little problem with a good simple plan. but keep the above in mind

 

[MeMol]

might not be able to horrizontal wet vent much of it remember the kitchen , and laundry must connect to mainline down stream of any fixtures being wet vented in horrizontal fasion.
I looked at your drawing having a little problem with a good simple plan. but keep the above in mind

The plan is to run a main line from the hall bath across the house to the exit point. I had planned to run kitchen sink drain straight down to the main line, so it would join the main line after the hall bath but before the master bath. Are you saying IPC won't allow me to put the kitchen drain line into the main line before the master bath ties in? I doodled it out, red dots are vents and yellow are cleanouts.

 

[Jeff H Young]

Thats about how I envision it . i like extending the cleanout to outside as well. you need clean outs at kitchen and laundry.
a lot of trenching Thats the part I dont like but guess you are pretty close

 

[Reach4]

One of the statements in that URL I placed says " Not more than one wet vented fixture drain shall discharge upstream of the dry vented fixture drain connection." To meet that, I think you will need to bring the tub/shower in downstream of where the lavatory drains.

So you could either move the lavatory drain entry or the tub/shower drain entry.

 

[Jeff H Young]

tub / shower (bath 2 ) has only one upstream wet vent of the lav , as the w/c happens to be dry vented . If there is a issue as Reach 4 brought up the pipng to the lav could actually be omitted and where the branch for tub was Id run a 2 inch and on the lav wall put a 2 inch combi (or 2x2x1 1/2 on its back) the riser will serve as vent and lav the 2 inch will go accross room to tub drain (your code might allow 1 1/2 to tub but id personaly go 2 inch ). additionally it might be ok for this to serve as vent for w/c Im unsure , also might be able to remove that jog in the main downstream of the bathroom

 

[MeMol]

Thats about how I envision it . i like extending the cleanout to outside as well. you need clean outs at kitchen and laundry.
a lot of trenching Thats the part I dont like but guess you are pretty close

Doesn't the removable trap on kitchen sink count as a cleanout though? I figured I need a co at the laundry room, that's easy. But the sink has a large porch behind it and I'd rather not have a cleanout stubbed up in my porch floor...

Yeah it's a lot of trenching, which sucks. At least we won't be digging it mostly by hand, got equipment for that!

 

[MeMol]

tub / shower (bath 2 ) has only one upstream wet vent of the lav , as the w/c happens to be dry vented . If there is a issue as Reach 4 brought up the pipng to the lav could actually be omitted and where the branch for tub was Id run a 2 inch and on the lav wall put a 2 inch combi (or 2x2x1 1/2 on its back) the riser will serve as vent and lav the 2 inch will go accross room to tub drain (your code might allow 1 1/2 to tub but id personaly go 2 inch ). additionally it might be ok for this to serve as vent for w/c Im unsure , also might be able to remove that jog in the main downstream of the bathroom

Simplifying the piping by running tub drain and sink drain together makes sense. I wondered if that would be ok.

The jog in the main branch is there because of where the line has to leave the house (no more than 14' from the front of the house) due to location of pre-existing septic tank. I'd rather put 2 45s in that line somewhere vs having to put 2 90s after it leaves the building to get it into the septic tank. Seems like it would be less likely to clog.

 

[Jeff H Young]

Simplifying the piping by running tub drain and sink drain together makes sense. I wondered if that would be ok.

The jog in the main branch is there because of where the line has to leave the house (no more than 14' from the front of the house) due to location of pre-existing septic tank. I'd rather put 2 45s in that line somewhere vs having to put 2 90s after it leaves the building to get it into the septic tank. Seems like it would be less likely to clog.

definatly ok to wet vent tub off line from lav . 8 ft max at 1/4 inch perft fall for 2 inch trap arm 6 ft on 1 1/2 trap arm.
Im talking about the jog in the main on way to the secondary bath is there a reason for that ? perhaps for distance from main line for clean outs ?
Im also thinking it might have a way to only branh off the main once and use that vent (at the secondary ) for all three tub , w,c and lav

 

[MeMol]

definatly ok to wet vent tub off line from lav . 8 ft max at 1/4 inch perft fall for 2 inch trap arm 6 ft on 1 1/2 trap arm.
Im talking about the jog in the main on way to the secondary bath is there a reason for that ? perhaps for distance from main line for clean outs ?
Im also thinking it might have a way to only branh off the main once and use that vent (at the secondary ) for all three tub , w,c and lav

Yeah, the jog in the main line is there for a reason. The septic tank is pre-existing and we either need the pipe to exit the house no more than 14' from the front, or we will have to 90 right then 90 left after it leaves the house to get it where it can tie in. Seems simpler and less likely to clog up just to put 2 45s somewhere along that line and have it leave the house in the right spot.

 

[Jeff H Young]

Yeah, the jog in the main line is there for a reason. The septic tank is pre-existing and we either need the pipe to exit the house no more than 14' from the front, or we will have to 90 right then 90 left after it leaves the house to get it where it can tie in. Seems simpler and less likely to clog up just to put 2 45s somewhere along that line and have it leave the house in the right spot.

keep your same exit of building on downstream end just get rid of the 2 45s . main line can go straight through the house no bends . you are correct less bends less clogs