Slab Rough-In

[J Bone]

I am embarking a project to remodel a half bath to a full bath on the ground floor of a high ranch. (on slab). After getting a couple estimates on the rough-in plumbing, and seeing that they were more than anticipated, I think I am going to give it a shot. I do most everything….framing, drywall, electrical, etc., and can sweat pipes OK, and recently re-did all of the plumbing in the laundry room, replacing steel with PVC and putting it in the wall. With the help of the pros on this site, I figure I’ll have the answers to some questions I have and will be more confident in tackling this project.

I am confident with running the supply lines and also the waste lines, however, I am a little unsure with the venting and also “tying” in the new PVC waste lines to the existing cast iron. To make it easier to follow, I have attached a photo of the existing gutted ½ bath….The 4” cast drain is the waste for the upstairs bath/kitchen sinks, tub, and toilet, and also the existing toilet drain in this half bath (or what was anyway). The 2” galv. steel pipe is a waste pipe for only the lavatory sink that was here originally, and I guess the vent for everything else.



New bathroom will be twice as big, toilet stays in the same spot, sink is being relocated, and I will add a 32’X 60’ shower.

I had some preliminary questions about doing the demo/waste rough-in:

1.) Should I saw cut the trench on the sides 1st with a circular saw/concrete blade and then just jackhammer away?

2.) I was going to run 2” PVC waste lines (1/4” per foot slope) for the shower & sink. Is this OK do do under the slab, and is there anything I should be aware of like putting something under the pipe or insulating it before I bury and fill the trench w/concrete?

3.) Since the room is gutted, I figured it would be a good opportunity to replace the waste line of the tub upstairs w/PVC and also remove the lend bends from both the upstairs toilet and the existing one (once I jackhammer the slab). A friend of mine did this recently and had to soften the lead with an acetylene torch to remove it and replace w/ a Ferco “donut” type fitting and PVC closet bend. Should I replace these bends since I am doing the work, or will they last at least another 30-40 years?

Sorry this is so “long-winded”….the wife is on my back looking to start this project, and has confidence in me to do this (strange) and I just wanted to see if I could get some answers so I could begin the demo phase.

Thanks

Jon

[LazyPup]

It would be advisable to cut the score lines in the concrete before breaking out to help keep even sidewall lines and prevent running cracks into the existing floor.

Check with your local code authority before starting. The minimum drain size for the toilet is 3" and the minimum for a shower stall is 2", hower, many local codes limit all underslab drain lines to a minimum of 3".

All horizontal drain lines are required to have a cleanout on the upstream end and at each change in direction which is 45deg or greater.

A toilet is required to be on the upstream end of a waste arm or horizontal drain and it only requires the closet flange as the toilet can be lifted to provide cleanout access at that point.

Both schedule 40 PVC and schedule 40 ABS are approved for underslab but you may not mix PVC with ABS. Whichever material you choose, you must run all pipe and fittings in the same material.

The pipe MUST BE laid with the writing on the pipe wall on the top of the pipe. (If you are required an inspection and the inspector cannot see the writing while standing above the trench the pipe will not pass inspection.)

You are required to use both primer and glue on all joints. (Hint-if you are required an inspection be sure to use a primer with the purple dye so the inspector can be sure you used primer.)

All walls and trenches must be left open and all piping exposed for inspection. After inspection you will be notified by the inspector that you may backfill or close the walls.

The closet flange elevation must be set so that the underside of the flange is flush with the finished floor and the top surface of the flange 1/4" to 3/8" above the finish floor. (The code prohibits the top of the flange from being flush with or recessed below the finished floor. You must consider what the finish floor is going to be, if you are planning a wood floor or ceramic tile you muat allow for that thickness as well.)

For the water supply you may use CPVC, PEX, roll or rigid Copper type K&L (No type M under slab), and galvanized iron pipe (iron pipe must be factory wrapped and all fittings must be field wrapped to the same level of protection.) You may not use PVC for any potable water distribution lines within the structure)

All coppper joints below the slab MUST BE brazed wrought copper fittings. (Common copper sweat fittings and lead free solder are prohibited.)

All piping should be sleeved where it passes through the finished concret floor.

Any transition from galvanized iron pipe to copper MUST BE made by means of a dielectric union, nipple or a 6" hardened bronze nipple.

Mechanical joints (unions or threaded fittings) may not be made on copper in a concealed location.

[mrcaptainbob]

Don't bother with using you're skillsaw with a concrete blade. It'll work...for a bit. It uses up blades, runs the pwoder through your saw, and requires more power than most handsaws can deliver. Rent one with the diamond, dry run blade. Better than that, rent the chainsaw for concrete. It allows a cut to a corner without having to overcut as with a circular saw. Imperative to wear a full face mask, eye and ear and nose protection. Put an exhaust fan in the window in the room your using and put it on high. That powder will go through the house and WILL make your wife REALLY unhappy! Oh yeah. Make sure to shut off your furnace if it's hot air. That will suck the powder through the cold air returns and make a mess in the furnace ducts.

[J Bone]

Thanks for all the info, it helps out a lot. Just let me know if this gets to be too much and I’ll stop w/ the questions…..


How do I put a cleanout on the drain lines if they will be buried below the slab? Or are you just saying install elbows with the cleanout in them even though this is true?

The attached photo shows my plan of attack with the waste lines – one from shower and one from sink and just T them together and then over to 4” cast to tie into. Could I tie the drain line into the 2” steel pipe instead or is this a big no-no?

http://www.homerepairforum.com/images/uploads/2005-3-10_jbone2_w550.JPG[/img]


The line I drew going up the wall was a continuation of the sink drain, and I intended to run this up through the ceiling, over and tie-in to the existing 2” steel pipe (see previous post for photo, just to the right of the 4” stack). Can I do this to vent everything? That’s where my confusion lies, in how plumbing should be vented.

I don’t follow how my current plumbing is vented. The two toilets, upstairs tub and sinks all drain into the 4” cast pipe, however, I see only one vent on the roof, which I believe comes from the 2” steel pipe. But the 2” steel pipe is only a drain for the sink that was previously here. Does everything upstairs like the sink, tub, and toilet tie in to that 2” steel pipe somewhere in the wall for venting purposes?

MrCaptain Bob –
Good advice, I’ll be sure to seal the area off good before I begin sawcutting

Thanks

Jon

[LazyPup]

The venting will be dependant upon which code is in effect in your jurisdiction because the International Residential Code and Uniform Plumbing Code takes totally differing views of venting.

As you can see the IRC will allow the 2" to run a max of 8' from the shower trap to the vent while the IRC will only allow 5'. (if you are under the UPC and the line will exceed 5' enlarge the line to 3" and you would be allowed 10') Guessing from the stud spacing it appears the run is about 5' +/-.

Somewhere on your structure there should be a main vent running up through the roof that runs undiminished in size from the main drain. (If the main drain is 3" the main vent is 3")

Auxillary vents may be reduced to 1/2 the diameter of the line they serve, but not less than 1.5", once they are 6" above the flood level rim of the highest fixture served. (6" above the sink in the illustration)

The UPC does not permit any horizontal vents. All vents (main and auxillary ) must run up through the roof. They may be offset providing the maximum angle of the offset is 45 deg from vertical. If you live in a climate that is subject to freezing temperature the vent MUST BE enlarged to 3" at least 1' inside the attic space before penetrating through the roof to prevent frost closer. (In homes with good insulation it is best to increase the size near the attic floor because the attic space may also be a potential frost area.)

The IRC allows horizontal venting, through the wall venting directly to the outside and termination in the attic space. (Terminating a vent in the attic space is a very bad idea. It allows excess moisture in the attic space that will damage insulation and also allows sewer gasses to collect, which will later come down through plumbing, HVAC or chimeny chases and be an odor problem in the living space.)