Mystery pipes in basement - where do they go?

Question

Newbie to the forum here. Will upload photos this evening, but thought I'd start with the question/context:

Just bought a fixer upper farmhouse in Portland, OR area. House is at least 1930s, could be older (long story). We also don't know if it was originally post and beam with foundation added later, but it's safe to assume that the house's sewer connection was only added in the late 40s/early 50s when the surrounding farm land became a neighborhood.

The house sits on half crawlspace, half unfinished basement. In the basement area, the sewer line leaves the foundation approx. two feet up the wall, then runs approx. 19 feet to the sewer main. A sewer scope has shown this line to be clean. There's an exterior clean-out, but the plumber couldn't find it.

Back inside, there is also a basement floor drain (below the sewer outtake). It appears to be old galvanized, and does not have a p-trap bypass. To me, this suggests it's not sewer, but after sucking with a shop-vac over the pipe opening it certainly smelled like sewer. I poured ~1 gallon of water down the hole and it drained well. There is a lot of visible debris, though.

Additionally, there are two 2" PVC pipes that drop vertically into the floor of the basement (again, below the sewer outtake). One is a drain for both the bathroom sink (upstairs) and the washer (in basement); the other appears to be a vent (goes up through the floor), but am still trying to determine. There is no sump/sewer pump in the basement.

One last detail: public records of the local sewer system indicate that my property has two sewer laterals. I have no idea where the second one goes, but it appears to be further away from the house.

My question(s), then: Is it possible the floor drain and 2" PVC pipes connect to the main sewer line out of the house? Aside from scoping them (the original scope didn't inspect these), is there an easy way to find out? Alternatively, could they go to the second mystery sewer lateral, or to a drywell?

Thanks everyone, apologies for the novel.

Answer 1

Thanks everyone for the feedback and tips! Turns out I was able to get a clear answer by calling the sewer company:

1) They looked at their recent scopes and confirmed that our property does indeed have two sewer laterals. They also observed some corrosion and decided to come out and take a look.

2) They brought a truck out to our house and performed a sewer scope - entering from the manhole immediately downstream and running upstream to where our laterals connects to the main line.

3) They then had me run water from every fixture in the house, one after the other. Turns out that all fixtures run to one lateral, confirming that our basement pipes do indeed tie into it somewhere out in the yard. The sewer guys theorized that what the inspector mistook for an exterior cleanout was actually the basement pipes tying in! Our second lateral is "inactive," but is likely an old stormwater drain for our back patio...which may or may not be legal.

Thanks again for the suggestions. Glad we got this mystery figured out! Now to determine how old this place is (we have aerial photos proving the home was there prior to the build date on tax records)...

Answer 2

Near the sewer main you may find a bidirectional cleanout, and be able to observe the sewer flow. Go upstream and dump dye into the water (Fluorescent Green Dye for example) and see where it comes out. Special purpose dye is available, or just use food coloring.

With a house that age anything possible, except water running uphill.

Answer 3

I had a home from the 30's in Illinois. It had a soak a way for the kitchen sink, bath sink, and bath tub. The septic tank was only for the toilet. It ran out of the side of house about 15' and was a 240 Gallon metal tank with holes in it surrounded by pea gravel. I discovered all of this when I added the cloths washer. The soak away was 15' out the back and 20' long 3' wide and 2' deep filled with wash rock / creek rock. I also have a home in Tenn. that had the washer water drain run into a water way down away from the house. All of these issues were corrected. I would check to see if you have lower elevation around your lot to where it could run.