Ask Me Help Desk - Basement Bathroom Rough-In

Good afternoon. I am overhauling my basement and I have removed a 10' x 10' section of slab in order to rough in the drainage for a new bathroom.

see layout: http://www.korteco.com/ben/floorplan.jpg

My first question is what size pipe (using PVC) should I use for my shower drain. I am using 4" for the stool, and 2" for the sink.

Also, Since my shower will be up against a stud-wall that is on the exterior basement wall, does that make it difficult to do all the copper pipework behind as you cannot access the back-side once the shower is in place?

Also, I will be transitioning from ~4" Cast Iron to 4" PVC on my main sewer line. Do you just use a rubber collar to make this, or is it best to use some reducers or other piece?

Oh you, one last Q... do you put a p-trap on any basment drain pipes?

Thanks,
Ben Horstmann
St. Louis, MO

Hi Ben,

You'll use 2" for the shower drain. Lots of showers are installed on block walls. Just be sure that the shower valve you install has integral,(screwdriver) stops where the supplies connect so you can service the valve. You could use a Fernco Neoprene cast iron to PVC to convert from PVC to cast iron.
"Oh you, one last Q... do you put a p-trap on any basment drain pipes?"
You might have added that question as a afterthought but it's liable to become your biggest hang up on this job.
First off every fixture has to have a "P" trap, no exceptions. but that's just the start of your problems. I don't see the first vent in your lay out. If you're counting on the vent stack you're otta luck unless it doesn't drain a bathroom up above and even then you must revent back at least 6" above the flood rim of the highest fixture that drains into it. Also code forbids discharging a major fixture, (toilet) past a unvented minor one, (Lavatory or shower). You may not install a "S" trap on a unvented fixture which is what it shows you planning on doing ,( "S" traps are outlawed in every state including Canada). You were planing to trap the fixtures weren't you? Because if you weren't you would be giving a direct open line to the sewer and access to sewer gas in your home. If you could reconfigure the fixtures perhaps I could give you a lay out that would work. If not you're going to hafta run a individual vent on the lavatory and the shower, tie them together and revent with 2" back up stairs or in the attic. Let me know what you decide. Regards, Tom

I see your point w/ the vents. Do people ever send a 2" vent out the side of a house (asthetics aside)? I don't see how I could get a 2" vent through two more floors.

Also w/ the traps, I was planning to trap all of them. The current plumbing for the old shower was a simple P under the slab, that is what I was planning on doing for the shower and sink. (Does the toilet need one or does it contain it's own trap within the toilet base?)

Based on using p's under the slab (no s's), and venting somehow out through the side of the house does this sound somewhat typical? As long as I'm not using unvented shower and sink I'm OK do discharge the toilet before them right?

Thanks again.

Quote:

Originally Posted by benhorstmann

I see your point w/ the vents. Do people ever send a 2" vent out the side of a house (asthetics aside)? I don't see how I could get a 2" vent through two more floors.

Also w/ the traps, I was planning to trap all of them. The current plumbing for the old shower was a simple P under the slab, that is what I was planning on doing for the shower and sink. (Does the toilet need one or does it contain it's own trap within the toilet base?)

based on using p's under the slab (no s's), and venting somehow out through the side of the house does this sound somewhat typical? As long as I'm not using unvented shower and sink i'm ok do discharge the toilet before them right?

Thanks agin.

Hey Ben,

Will you pull a permit and will this be inspected? If we can change the shower so it connects with the lavatory drain I can come up with a layout that will vent everything without having to run a pipe to the roof of out the side of the house. All toilets have a built in trap. Regards Tom

Quote:

Originally Posted by speedball1

Hey Ben,

Will you pull a permit and will this be inspected? If we can change the shower so it connects with the lavatory drain I can come up with a layout that will vent everything without having to run a pipe to the roof of out the side of the house. All toilets have a built in trap. regards Tom

Yes we will be getting it inspected. I figured this out. I did have two more very small questions. First off, for the "dap out" for the shower drain, does the 14"x14" area get centered on the shower drain hole, or do you keep it more towards the front of the shower allowing for more room to mess w/ the traps.

Also, I have seen you routinely say that 2" is minimum for a shower drain no exceptions, although every tub drain assembly w/ lever plug I have found is 1 1/2". Is this acceptable to use or are they selling products that aren't to code.

Thanks again, this forum is wonderful.

Quote:

Originally Posted by benhorstmann

Yes we will be getting it inspected. I figured this out. I did have two more very small questions. First off, for the "dap out" for the shower drain, does the 14"x14" area get centered on the shower drain hole, or do you keep it more towards the front of the shower allowing for more room to mess w/ the traps.

Also, i have seen you routinely say that 2" is minimum for a shower drain no exceptions, although every tub drain assembly w/ lever plug I have found is 1 1/2". Is this acceptable to use or are they selling products that aren't to code.

Thanks again, this forum is wonderful.

Hi Ben,
The 14 X14" dap out is for a bathtub not a shower. We bring the shower trap raiser up exactly under where the shower drain will go and pour around it. Bring the raiser about 3" up off the cement. If you're installing a tile shower the drain can go any where you wish. What type of shower were you planing? Tile shower from scratch? Shower enclosure with a base? The 2" is the pipes up to and including the trap. This will give you better drainage then 1 1/2" drains. While the tub waste and overflow and drain are indeed 1 1/2" they don't clog the way drain pipes do. Regards, Tom

It is a shower tub, sorry if that was unclear.. so a dap out for a tub drain.

Thx for the info about the drain and overflow, I still have 2" stubbed to the local.

So about that dap out :confused:, 14"x14" centered on the drain hole of the tub?

Thanks again

Quote:

Originally Posted by benhorstmann

It is a shower tub, sorry if that was unclear.. so a dap out for a tub drain.

Thx for the info about the drain and overflow, I still have 2" stubbed to the local.

So about that dap out :confused:, 14"x14" centered on the drain hole of the tub?

Thanks again

"14"x14" centered on the drain hole of the tub?" Correct. The reason the trap's exposed in a dap out is that you'll be connecting the tub waste and overflow to the trap below the floor line. It also makes repair much easier if you have to replace the tub drain. Regards, tom