[scirocco70]

Here's the situation:

There is a 3" cast iron main stack in the house (built in 1969, in MD, code is IPC) that empties into a 4" CI (with cleanout) pipe that exits through the cinder-block foundation. The pipe comes out of the foundation 14" below grade on the outside. I have uncovered it, and followed it until it makes a long-sweep 90 deg turn, and continues on towards the septic system.

I need to tap into this pipe further along, towards the septic system, and add a section with 3" combo-wye to serve as a drain for the sewage-ejector package I want to install in the basement.

I've uncovered the pipe where I want to connect, and am comfortable punching the hole through the block wall. I know that I need to install a 2-size larger sleeve (tho the old one does not have such a sleeve) and use a waterproof seal between them.

I also have read (searching this forum gives a lot of info!) that the best way to connect PVC DWV pipe to CI is fernco or similar clamps.. neoprene and stainless steel.

The questions I have are:

1) What is the best way to achieve the "waterproof seal" between the DWV pipe and the sleeve? Will "Great Stuff" foam work?

2) Is another PVC pipe (4" for a 3" pipe) sufficient for the sleeve? Should I use Sch 80 instead of 40?

3) Is there an advantage to using Sch 80 for the whole project? I'm a little concerned about burying the PVC; if the existing pipe had been PVC I probably would have cracked it while digging it up. Would this cause matching problems with the thickness of the original CI pipe?

4) Most important... are Fernco clamps OK for direct burial? I can find nothing in the code that addresses this, but I'm not sure that long-term outdoor burial of metal clamps (even SS) is a good idea. Is there an alternative?

5) And finally, what is the best slope for the new attachment? The original exit pipe drops 10" over 28", a really steep drop. I know that 1/4 over 10ft is minimum, but is more bad? I have heard that you never want the "pee to outrun the poo" as that can cause blockages... It is to my benefit to penetrate the foundation as low as possible, but I certainly wouldn't want the outside pipe to backup into the house...

Attached is a small diagram of my situation, a top view and side view. The only part that isn't clear is how steep the short pipe that exits the house is... it comes out of the house at 14" below grade, 28" away from the long pipe, which is 24" deep. I guess that's about a 25deg slope. The dotted-line represents where I want to put in the new drain.

Also, I DO intend to pull a permit and have this setup inspected, and have taken and passed the homeowners plumbing license test for my county (never heard of these before, but... it's the rule here. The test was free.)

Thanks in advance, and sorry for the long post!

~aaron

[letmetellu]

Number 1. If I understand your question right you will not need any sealant. The fernco adopter or what ever you use will seal against the PVC and also against the castiron pipe.

Number 2. That is a good idea to use the larger PVC thimble or sleave to run the smaller PVC through. It does not have to be schedule 80, schedule 40 will be great.

Number 3. Schedule 40 is used all over the country in underground work, I would rather have the smooth inside of PVC than the rusted and possibly cracked castiron.

Number 4. Fernco will work in the underground situation, and the stainless steel is also good to use. I am sure neither are permanent but what is.

Number 5. The 10" drop is not all that bad in that short of a distance but if you want to come out of the foundation higher then you could lay your Wye that you are going to put in the line on it back or on an angle towards the pipe you are going to connect to and then run a short piece up to a 45 degree ell at the end up the pipe that comes out of the foundation.

It might be to your advantage to ask the plumbing inspector if what I told you would pass before you install it.

[scirocco70]

Thanks for the response Letmetellu!

Here's my take on your answers...

1) No, I wasn't clear... I mean, how do I seal the space between the sleeve (ie the larger pipe) which the 3" goes through. There's going to be a gap, and obviously it needs to be sealed with something. Mortar? Foam? Oakum stuffing?

2) This is currently code in my area, so.. i'll be doing it!

3) But obviously Sch 80 is significantly stronger. I do NOT want to dig this thing up again, not even in 30 years, so the extra cost/hassle for Sch80 is not relevant. The real question is, since the pipe wall thickness is different (thicker), will it still mate effectively with the inside diameter of the existing 4" CI pipe. Clearly a smooth, no-step transition is desirable.

4) Do you know if there's code that addresses this? I'm under IPC, but I haven't found a reference in it yet. "explicit allow" makes me happier than "implied allow" ;-)

5) I would prefer to come out of the foundation as low as possible, so as not to have to lift so high from the sewage ejector... but I don't want to come out low enough that a large influx from upstream (main stack of house) would back up, even a little, into the new 3"

Is there a pee-outrun-the-poo issue, or is that just wild conjecture?

Thanks again!!

[letmetellu]

Yes you do want to seal where the pipe comes through the foundation And any of the things you names will be OK. Schedule 80 is just over kill, the outside diameter of the schedule 80 is the same as the schedule 40 PVC and neither one of them is going to fit snug going into the 4" cast iron but you can buy a fernco adaptor or a no-hub neoprene adapter to make a tight joint where the two join. There is some truth to the pee and poo thing but for this short distance it will not matter at all for you.

[iamgrowler]

Thanks for the response Letmetellu!

Here's my take on your answers...

1) No, i wasn't clear... i mean, how do i seal the space between the sleeve (ie the larger pipe) which the 3" goes through. There's going to be a gap, and obviously it needs to be sealed with something. Mortar? Foam? Oakum stuffing?

Since the code doesn't specify which sealant to use, it is always best to check with the local authority to find out what they prefer you use.

Personally, I've started using epoxy grout.


I just mix it up and then use a mortar bag to inject it into the void and then finish it off with a trowel.