Finishing a basement - poured 3' too low for sewer

[David Mac]

Hi all, frequent reader, first-time poster. Just bought a home with the intent of finishing out a walkout basement. Relevant info: I'm in GA, which has adopted IPC 2012.

Put together my plans for installing a WC, two lavs, and a shower; all the stubs had been put in place already by the original builder. Then I discovered a 3" drain stack that ran the whole length of the house instead of straight down into the waste stack for the basement fixtures. Why, I asked myself.

Got in touch with the original owner/builder - he said what the county told him the sewer depth was, and what it actually turned out to be was off by 3', which meant he had to re-route the 1st floor and above to a different drainage system and couldn't use what he'd buried under the foundation. Bummer.

But the pipes are still there, and they feed outside the house (all the way at the other end of the slab from the stubs) and are ready to be connected to... something.

A couple of options I have, then - and would like to hear opinions/others before I hire it out to a master plumber.

(a) Install a macerating toilet, upflush into the rerouted stack, and use gray water undersoil irrigation from the lavs and shower. (I don't think I'll choose this, as it probably requires too much additional concerns from the gray water system.)
(b) Install an ejector pump
(b1) Break foundation and install it inside the basement - discharge into existing line (and vent - can I combine with another dry vent system, or do I need dedicated? Are most ejector pumps considered "pneumatic" per IPC 2012 906.5.2?)
(b2) Install it in the pipes that feed outside the house and inject it back into the house (how to protect against freezing? Jan avg. low is 29F), venting at ground-level (will it stink up the neighborhood?)

I'm expecting these to all be low-use fixtures, only in use when the MIL is visiting.

Thanks all for your help!

 

[Reach4]

You can put in a sewage pit with a grinder pump. This pumps up through a checkvalve to join the higher sewer. This pit needs to be vented. Some require a 2 inch vent, and some places allow a 1-1/2 inch vent or maybe even smaller. This would be your (b) or (b1) but note that the foundation is on the perimeter... it is not just any spot in the basement floor.

So you would intercept the under-basement sewer line and put the pit there.

Pneumatic means air. http://www.carterpump.com/pneumatic_ejectors.php says

What is a Pneumatic Ejector?
The pnuematic ejector is a extremly simple yet reliable mechanism. Fundamentally, it consists of a receiver or "pot' that allows liquids and solids to enter without restriction. When the pot becomes filled, compressed air is introduced to displace the contents up to a higher discharge line.
​

I am not a pro.

 

[Sponsor]

 

[Cacher_Chick]

Install an ejector pump. There is no great benefit to doing it any other way if you cannot gravity drain.

 

[David Mac]

Thanks for the replies. I'm definitely now planning to use the ejector; the only question is, inside or outside the house? I found the main stack and cleanout and part of my lateral yesterday - it's about 8" below grade on the side of my house. I haven't found the connection yet where the underslab DWV comes out.

The frost line is about 6" in my area. If I installed an outside ejector system, could I effectively bury all the pipes - with a valve cover for the shutoff and check valve? Can I vent the pit directly outdoors, without running a vent pipe up the house, by using an activated charcoal cap, similar to a septic?

 

[Reach4]

The frost line is about 6" in my area.

I am very skeptical of that if you are talking about Albany.

 

[Sjsmithjr]

The frost line is about 6" in my area.

I see in your first post that the house is in Georgia. Check your local building codes department as most areas adopt 12" for frost line depth even if the actual frost line is less.

Can I vent the pit directly outdoors, without running a vent pipe up the house, by using an activated charcoal cap, similar to a septic?

Again, you'll need to check with your local building codes department and "vent per local code". You're going to need a permit anyhow.

Good luck!

 

[Cacher_Chick]

The basin will need a vent, but this will in no way exclude you from needing to have a proper venting system for the fixtures in the house.

 

[David Mac]

Cacher_chick - Agreed. When roughed in by the builder, there are dry vents for both lavs and a wet vent for the WC and shower. Based on my understanding, this will meet Code. Image attached - I intend to use the ejector between "Need to find this" and the cleanout popup - again, either inside (breaking concrete) or outside.

I have filed for permits for the finishing; the discovery I need an ejector has come while waiting for issuance (3 weeks and counting...). I called and left messages for the inspection dept. to discuss, but haven't heard back on what to do to amend my permit filing. I've got two tradespersons coming this weekend to give me first and second opinions on the work.

 

[hj]

IF you install it outside the house, the first time it will require service, you will regret your decision. In the first place it will be a LONG way down.

 

[David Mac]

IF you install it outside the house, the first time it will require service, you will regret your decision. In the first place it will be a LONG way down.

Hj - why in particular would outside be worse than inside? I would naively think that not breaking concrete would be simpler.

Thanks,
David