Ask Me Help Desk - Install New Basement Half Bath Over Slab

Hello,

I plan to install a new half bath in a basement which has a concrete slab. The house is in Philadelphia. The main waste stack is 4" cast iron and it goes out to the city sewer under the slab. I want to find the horizontal run of the waste line under the slab and tap into it for the new toilet.

Here are my questions:

1. Does anyone know if the code in Philadelphia requires that I tap into the horizontal run with cast iron? Or can I use a PVC wye with shielded hub-less connectors and clamps, etc.?

2. If I can use PVC, is there a particular PVC thickness for use under the slab or just the stuff sold at the local retail giant?

3. What is the preferred size for the toilet waste line? Is it 3" or 4"?

4. Regarding venting, must I install a vent for the toilet? I've heard something about "Philadelphia Single Stack venting" and was wondering if there is a way to get away without it.

Thanks in advance!

They have their own code so its up to you to read. http://www.phillyriverinfo.org/WICLi...umbingCode.pdf 3" or 4" is fine, use 3" most of the time to get into tight spaces. You must vent all of the fixtures in your new bath not just the toilet. Is there a stsck in the basement now that you can tap?

Quote:

Originally Posted by ballengerb1

They have their own code so its up to you to read. http://www.phillyriverinfo.org/WICLi...umbingCode.pdf 3" or 4" is fine, use 3" most of the time to get into tight spaces. You must vent all of the fixtures in your new bath not just the toilet. Is there a stack in the basement now that you can tap?

Thanks very much for your reply.

I had read the code and found it hard to interpret (or maybe I just didn't like what I was seeing) so I was looking for some local knowledge. Here is the (I believe) relevant passage:

[Plumbing Code Excerpt]
P-902.2 Underground sanitary drains. Underground building sanitary drainage within a building and beyond the building wall to the street, including site work, shall conform to one of the materials and standards listed in Table P-902.2.

Drainage systems for corrosive industrial wastes shall be of acid-resisting cast iron or other material that is
resistant to corrosion and degradation for the concentrations of chemicals involved.

TABLE P-902.2 — UNDERGROUND SANITARY DRAINAGE PIPE MATERIAL STANDARD

Cast iron pipe ASTM A 74; CISPI 301
Concrete pipe a ASTM C 14; ASTM C 76; CSA A 257.1; CSA A 257.2
Copper or copper-alloy tubing (Type K or L) ASTM B 75: ASTM B 88: ASTM B 251
Ductile iron AWWA C 151
Vitrified clay pipe a ASTM C 4; ASTM C 700

Note a: Not permitted underground within buildings nor within 10 feet of the building foundation.
[End Plumbing Code]

So now I am thinking that the way to go may be either to put in a cast iron wye with a 3" copper run to the toilet? Or instead of the wye perhaps some sort of saddle into the cast iron. Is that even reasonable?

I will vent every fixture the same way. I did not mean to imply that I would vent some fixtures and not others. I was just hoping that there was not a requirement because of this Philadelphia Single Stack configuration I've heard about.

To answer your question about there being a stack in the basement into which I could tap, is not so simple. I can see the bottom of the stack (and a clean out hole) but it does not go directly into the slab. Rather there is a 90 degree elbow and it is buried in a cinder-block / stucco knee high wall. The basement is actually a split level hence the knee high wall. The stack comes down and lands right between the two levels. I should also mention that the stack sits in a corner behind the furnace, so getting to it is no easy task in itself. I should mention that there is already a half bath on the upper level of the basement that I plan to remove. If I knew how all the pipes were laid out there is a chance that I could tap into the drain for the existing toilet. That drain is on the other end of the knee-high wall from the stack. I pulled that toilet off to see which way the closet bend goes and it turns toward the stack (see attachment). I am guessing that the stack and that toilet meet somewhere in the middle and connect to the horizontal drain out to the sewer.

I have attached a picture of the stack in the knee high cinder-block wall.

I appreciate all useful thoughts and advice. Sorry for such a long post. Again thanks for your input.

I hear you, I hate reading code. Tom Speedball1, Milo or Mark will read this tomorrow and have run at it. They are all plumbers who actual know codes, unfortunately different codes than this one

Thanks for your reply I look forward to advice from any other experts!

Hi all:

That Philadelphia plumbing code is from 1999... betting it is a bit outdated, but I can't be sure so I would recommend that you call a local plumbing inspector and simply ask him if PVC is allowed underground... it really should be as it is legal everywhere else that I know of... ;)

If, for some odd reason, you can't use PVC underground you'll definitely want to use the cast iron underground! You wouldn't believe what 3" and 2" copper pipe and fittings cost nowadays.

Another quick question will be to ask if WET VENTING a toilet is allowed in your area. If so, you can use the lavatory vent to "wet vent" the toilet and save yourself some money and time/labor regarding this 1/2 bath addition.

Check with the local inspector and then pop back and let us know what you were told. We can walk you through installation, tools, etc. when needed!

You will definitely want to plan on installing a 4"x3" cast iron NO-HUB wye fitting into the 4" horizontal drain and connect all using 4-band husky clamps. Once you know the pipe type allowed for the bathroom I can tell you how to transition to it... if needed.

Finally, I'm a bit confused when you say that you might be able to connect into the pipe from the other bath.. The attachement you mentioned did not upload? Let us know more here...

Mark

Quote:

1. Does anyone know if the code in Philadelphia requires that I tap into the horizontal run with cast iron? Or can I use a PVC wye with shielded hub-less connectors and clamps, etc.

Since PVC is not addressed in the material requirements you will have to contact your local Building Department.

Quote:

2. If I can use PVC, is there a particular PVC thickness for use under the slab or just the stuff sold at the local retail giant?

The thickness of the PVC drainage shall be schedule #40 PVC.

Quote:

4. Regarding venting, must I install a vent for the toilet? I've heard something about "Philadelphia Single Stack venting" and was wondering if there is a way to get away without it.

Again, contact your Building Department tom ask if wet vents, (see image )are allowed. Good luck, To

Thanks for all the replies.

I will talk to an inspector about wet venting and about using cast iron or PVC. In the existing half-bath I can't seem to find any venting at all.

In regard to tapping into the other bath room, I meant that perhaps I would be able to tap into the waste line from that toilet (which will ultimately be removed.)

I have attached a drawing of how I think everything ties together. However all the pipes in red / maroon are just my guess in terms of locations. Anything in Blue or Black is where things actually lie.

Thanks for all the help!

A lot of unknowns, for sure...

Check on the wet venting and then pop back and let us know what's up... OK?

Otherwise, you might also be interested in the SANIFLO macerating pump system... check it out at Saniflo macerating and gray water pumping systems You would be looking at the sanibest or saniplus for a 1/2 bath or larger, if I remember correctly! Basically, this system uses its own toilet but can use any sink you want to install. The system is a bit whiney when the pump turns on, but no need to break up any concrete and the system is very reliable and trouble free... ;)

Be clear, however, that I present this as information only and still recommend that you chip out the concrete and connect direwctly into the plumbing system... always best!

Mark

Mark