New 1/2 Bath in small existing closet

[dshilo]

Hello all,

Great site. I am a DIYer that is on IPC in NH. My home is one story slab on grade, I have a closet with a 4" cast iron stack vent and cleanout in it heading right under the slab and directly to the sewer main. I want to convert this room to a 1/2 bath by adding a sink and toilet. Please see attached for existing conditions picture, existing sanitary drainage diagram, and proposed sanitary drainage diagram, plans and elevation. A have been reading IRC 2009, and there are still a couple things I have questions on:

1. Please note that I'm hoping to use a graywater sink-toilet product from Spain - waiting for confirmation from the inspector on that one... not really a question here, just wanted to see if anyone's seen one of these bad boys before - very popular in the rest of the world. This doesn't have ASTM tests, but then again, neither do these, which seem to get installed all the time.
2. Since this is slab on grade, and I am trying to avoid breaking up the slab, I am putting in wall-hung fixtures, and going horizontally to the stack. I'm a little confused on requirements for a horizontal run with back to back sinks. Do I need a cleanout on those? Access would be tough...
3. The building cleanout is currently located right above the slab, but it will have toilets and sinks all around it once I'm done, so there won't be the minimum 18" access. Can I put the cleanout above all the fixtures as shown?
4. I would like to vent out the back of the house instead of the roof. By my reading of IPC, I only need half the diameter of the stack being vented, but the full 4" currently coming out of the roof gives me pause...

Can you seasoned veterans let me know how I'm doing here?

 

[CountryBumkin]

I saw a toilet-sink combo used on a project on "This Old House". I recall they needed a permit waiver to install it (space was the issue).
I'm not a pro. I would advise you to check for repair parts availability and verify thread size/pitch (for water connections) compatibility to US piping.
Looks interesting. Good luck.

See

And http://www.caromausa.com/database/files/library/Profile_Smart_USA_2016_WEBSITE.pdf

 

[Sponsor]

 

[dshilo]

I finally have an update on this project, and a couple of questions I'm hoping one of you experts can help with:

1. My pressure relief valve opens (and squeaks!) every time I turn off the water to any fixture. Also, I keep getting little drips here and there on connections I thought were solid (granted, I'm not a plumber...). Is my incoming water pressure just too high? Would the utility have to fix that?
2. I went and cut out the existing copper trunk and branch connections heading under my slab to the kitchen, and forgot to label them first. Have any clever tricks to determine which line is which without actually hooking it up and trying it?

Here's the current state of things:

Here's the pressure relief valve:

And here are those unlabeled pipes: