What would be the most probable path for the main drain of this floor plan?

[MiniMe4Eng]

Hi guys

I am having some issues with an opening in the concrete floor of a basement.
It seems that it was left there on purpose but a supporting small wall was build kind of on top of it leaving like a slot still exposed to air and humidity which created some problems that I am now trying to fix
You can see pictures here

http://www.eng-tips.com/viewthread.cfm?qid=416569

No I am trying to guess if this issue is somehow connected with a potential main drain issue
So my question is, considering the position of the sinks and the bath tubs showed in this picture, what would be the most probable path for the main drain ?
In the below picture
1 -the place where the city water pipes hit the house (outside the house under that window see the second picture below)
2 -the main valve for the entire house
3,4 -exterior drains used to connect the gutters to the main drain (I assume)
5-The brown spot on the basement floor is the flood drain for the basement

Considering the above what would be the most probable path for the main drain of the house ?
Does it usually run under the basement floor slab or outside the wall of the basement?
How do the gutters connect to the main drain (they go straight into these pipes close to the wall)

 

[bridgebuster]

I would assume the waste pipe is running on the inside of the wall marked "4". assume you meant to rotate the bath tub 180 degrees so that the drain is along the wall. Can you do some probing/digging at "5" to see if there is a lateral? Another thought, your municipality map may have mapped the house connections along the main sewer.

 

[MiniMe4Eng]

many tanks for the reply,
..yes looking at 5 is possible and I guess that will tell where on which side the waste pipe is located
Woul the municipality map more than the point where it reaches the house?

 

[bridgebuster]

Let me clarify what I meant by house connection: it's where your waste pipe ties into their sewer. In NYC, the sewer maps show them; the "house connection" is out in the street.

 

[MiniMe4Eng]

Hmm at 5 I removed the water from the trap using a wet vacuum and I could see the pipe going toward the North West corner of the picture.
I am not sure why it goes like that

I placed a request to see where the pipes are located
Here in Toronto the city has a service that provides that information for free

 

[MiniMe4Eng]

I think that I solved the mistery of these two "unknown buried objects" (UBJ)

The house must have had an interior oil tank like this

The above caps must have been installed after the tank was removed and the pipes cut close to the soil level.

There is a chance that this was an exterior oil tank still buried under ground but then what is the point of putting the fill in pipe and the vent so close to the wall of the house (14 inches). No matter how you position the tank the space for the tank would be insufficient unless you put the tank perpendicular to the wall and you decide to put the pipes (fill in, vent and the pipe that goes into the house) all at the end of the tank close to the house which looks stupid to me

 

[MiniMe4Eng]

After more research I have found this

http://www.sbphinc.com/2016/05/31/finding-external-plumbing-covers/

The second arrangement for sewers is a mushroom cap. These also black or grey and cast iron or plastic. They too are the vent for the trap. The mushroom cap is typically 6-12″ above the surrounding grade and they are usually located 5′ or more from the curb.