Basement Bathroom

[Rabid_Rabbit]

OK, I have a question on installing a bathroom in my basement. Here are my circumstances. In the basement I have all the waste lines running down to one 4 inch pipe then down the wall and exiting the basement about 2 feet up the wall in the direction of the septic tank. I'm guessing that this is the only waste line. But I also have rough in for a bathroom in the basement consisting of one 4 inch pipe with a rag stuffed in it about a foot from the wall and a single 2 in pipe capped right next to the wall. Also a wooden box in the floor five feet from the wall. My question is how can this possibly work? The washer and the utility sink both drain into a sump pump and it pumps it up to the main waste line. If there was a waste line under the slab why wouldn't they tap into that instead of the pump? I was going to pour water down the 4 inch pipe to see if it backs up before installing anything. Any help would be greatly appreciated.
Thanks Ethan.

[jimbo]

We don't often say "never" in plumbing, but we can say with some certainty that water NEVER runs uphill!

What's the story on that wooden box? Does the floor drain somehow run over there? It sounds from your description that the only way you could have a toilet in the basement is with a sump and pump. ( It would be a sealed sump, not like the one your sink etc. drains to.)
Another choice is a macerating toilet, which is also pumped but needs a smaller discharge.

In either case, you are going to need a vent. Could that 2" pipe you mentioned be a vent?

[Rabid_Rabbit]

I'm not sure I thought that the 2 inch pipe was for a sink, but I don't see any vent pipes. all the drains from the first floor just have 90's that attach to the main waste line. I know that there should be vent lines somewhere. We did have the house inspected before we bought it. The inspector didn't say anything was wrong with the plumbing, except a slow drain upstairs.(it was clogged with hair) I am at work but can add some pictures when I get home.

[Rabid_Rabbit]

Well when I got home I looked at the washer drain and it actually goes down into the slab near the sump pump. When we first move into the house the washer was draining into the utility sink which goes into the sump pump(which is sealed up tight). The washer drain would not reach the 2 inch pipe on the wall meant for the it so I just moved the 2 inch pipe like a foot closer to the washer. Also I did crawl around in the attic last night and did find vent pipes.
So it looks like there is a pipe under the slab because the waser has never overflowed.

Just as a side note when we closed on the house the guy said that he was a plumber by trade. I not a plumber and some of the plumbing looks terribel. like a 4 year old did it. I have had to fix many little things like the washer drain and the water for the fridge and the dishwasher. But this is about the basement bath room not how screwed up the plumbing is in my house.