Basement Bath

[imported_ssabin]

I had my builder install a basement bath rough-in for me, which inclused a sewage pit, and (3) 4" stubs coming up through the concrete floor. I also have a vent stack accessible that has been capped off near the "ceiling" of the basement. I will not be using the shower drain, have verified it is the one with a trap, and will be capping it off.

Conventional plumbing dictates that vent lines be installed within so many feet of the fixtures, but this sewage pit design appears to be different - does the entire system vent via the pit's 2" vent line? I can see how I would tie the sink drain into a tee'd vent line from the pit, but not the toilet. Does the 4" drain lines to all 3 fixtures make up for the fact that there is no dedicated fixture vent lines? I've looked at some internet literature for similar systems and the schematic seems to simply install a vent line from the pit to the vent stack which goes to the roof, and install the fixtures to the drains. Do I have this all wrong?

Also, my neighbor was complaining that this 4" thin wall drain pipe does not adapt easily to a toilet flange. He has already completed his basement bath whereas I am just getting it framed in. Is there an inherent problem getting a toilet flange onto a 4" thin wall drain line?

[Wgoodrich]

What you call a cap on your vent stack must instead of being a closed cap must be a vent check valve. It allows are to suck into the vent stack but not allow the air to leave the vent stack into the room. Be sure you have this check valve vent outlet on the end of that vent and not a cap closing off that vent stack or you have no vent stack operable.

You have a maximum of 8' using a 2" vent stack from the trap wier.

It does not matter if you have a 4" drain to a lavatory you still need a vent and trap. Without the vent your water will be sucked out of that trap allowing gases to enter your home. If you have a 4" pipe then you may go as far as 16 feet to the vent but if you have a 2" pipe you have a maximum of 8 feet to that vent. There is maximum distances allowed to install a trap from a vent to limit sucking the water out of that trap.

It is hard to visualize what you have but yes this vent with a check valve is evidently designed to serve as a stack vent.

HOpe this helps

Wg

[imported_ssabin]

Wayne,

I don't think I described the situation clearly enough. The basement has the sewage pit installed, (3) 4" drain stubs coming up through the floor and all tee'd into the sewage basin under the concrete, and in the floor joists above the basement is a cap providing access to the existing vent stack used by the rest of the house.

The sewage sump has (2) 2" holes, one for the discharge pipe and one for the vent pipe. I asked the plumber that did my house if there was a vent access in the basement, and he pointed me to it (it was hidden behind the insulation). He said that all that needs to be done is to connect the vent outlet from the basin to the vent stack that is barely exposed to the basement, and that's all that needs to be done in terms of venting.

I am simply asking is this really all that is needed? The furthest drain stub is about 8-10 ft from the sewage basin, so I guess the fixtures essentially get vented through the oversized drain lines which go to the basin, which is vented to the house stack? I could actually connect a vent line from the sink to the new vent pipe that I will be using to connect the basin to the vent stack, but I cannot tie in such connections to the toilet or the shower, and they are further away.



Vent stack located
vertically above
sewage pit

************
Sewage Pit * --------|sink stub|------|toilet stub|-------|shower|
************

|---------about 8-10 ft across---------------------------------------------|


The actual tees and such underneath the concrete are not known,
but I just drew a straight line for simplicity.

[Wgoodrich]

The 4" toilet has a trap built into the toilet as long as your toilet is no more that 16' with 4" drain to the outlet then the outlet may be used as the vent see below remembering 16' is allowed between the trap in the toilet to the vent.

IRC 2000 copied section.
SECTION P3105 FIXTURE VENTS P3105.1 Distance of trap from vent. Each fixture trap shall have a protecting vent located so that the slope and the developed length in the fixture drain from the trap weir to the vent fitting are within the requirements set forth in Table P3105.1.

As far as I can interpret what we are talking about that vent is not necessary for the toilet. The vent is requried for the sink within 5' and the vent for a shower is required within 8 feet of the shower. If you are within those limited feet to the outlet in your lift station then you are fine without a vent.

HOpe this helps

Wg

[imported_ssabin]

Thanks, Wayne.

I just checked my drawing of the basement, and it shows the sink to be 1 ft from the basin, the toilet 3 ft from the basin, and the shower 6'10" from the basin.

I'm just glad to know there is some factual basis for proceeding without any other vent lines.

The only thing I am still concerned with is the fact that most sinks are 1.5" drains, which will go through a 1.5" trap then down to the drain. Since the 4" drain stub is really a drain and vent line essentially, I would think that I need to minimize the length of sink drain line which is less than 4". Are there any guideline/rules for this?

Thanks again.

[Wgoodrich]

What I am picturing is you have no drain pipe that exceeds the limits that I mentioned earlier. There for you need no venting.

sewage pits drain the drains into an open pit thus breaking the siphon before you reach a distance requiring a vent.

You drains as you discribe non of which connects to a pipe rising to a level above the fixtures those pipes serve therefor non of these pipes fit the definition of a vent. Yet non of these pipes exceed the maximum distance allowed before a vent is required.

You drain pipes drain into an open pit area thus breaking any siphon affect before you exceed the distance allowed thus you outlets into the sump pit acts same as a vent action releasing the siphone effect to those fixtures and you therefore don't have concern of sucking your traps dry.

Each fixture whether sink or shower must be with a trap. You toilet has a trap built into the toilet so it already has that trap requried.

You have no piping that fits the definition of a wet vent, yet as you discribe what you have no venting is required except for the sewage pump.

You mentioned a vent in the basement serving your upstairs fixtures connected to a vent stack. That part available to you in the basement is below the upstairs fixtures therefor if you cut that vent pipe before it rises above those upstairs fixtures you then create a drain into the sewage pump negating the existing vent becuase you are below the upstairs fixtures where you are talking about tapping into that existing vent stack.

The last paragraph does not matter any way because your sewage pump requires an individual vent stack through the roof to serve it only.

Hope this helps

Wg