Drains- Guess whats under the concrete!- Sat morning mystery


Old 01-26-19, 06:00 AM
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Drains- Guess whats under the concrete!- Sat morning mystery

Redoing a house built 1978. All ABS drains. I'm hoping someone looks at this photo and is like, yeah, we did that in the 70s, and can tell me how this was built.

In opening the walls throughout the house, almost everything seems to code, a few blips here and there, worst thing i've seen is cutting structural 2x4s on exterior wall for 1.5" ABS. Already fixed!

OK, so in the basement, i'm more baffled by this.

Utility sink: I don't know where there was a p-trap ripped out by demo crew with the sink, but for sure i see a proper vent to roof, it is dedicated and not wet, traced it all the way up to roof, nothing splices in. I need to reuse this for a sink/backwash for salt-free softner system. Only thing is that is weird, zero septic gas comes out of this wall drain, even after a month of disconnect. No smell at all, makes me think there is water in between.. makes me nervous

Washer drain- I'd like to re-use with a washer on first floor (with a new vent to roof and p-trap upstairs). But i'm baffled how this existing could be vented (there are no additional vents on roof anywhere nearby besides the sink one), and whether there is a p-trap in the dirt under the concrete? Again, zero smell coming out of drain. I ran a hose full-on with water for 10 min into it and it handled it like a champ. How could this be?

Floor drain- Did they tie these into the septic line? I see water not fully drained in what looks like a 90 elbow a few inches into the drain that faces the septic line. Not sure though.

The water on the concrete is from me removing the water heater.

So i'm baffled on the layout and what is under the concrete, and how i can tie into it all up to today's code.

Any insights are much appreciated!
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Old 01-26-19, 06:54 AM
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The utility sink looks good. You'll add a P-trap under your new sink. No worries about it not smelling, they don't always. I'd still put a rag in it during construction. You can put a trap on it and standpipe like a washer, and use that for the drain. Or add a sink back in and drain it there.

Can you look down the washer standpipe? Maybe the trap is under the slab? It's not typical, but possible.
Old 01-26-19, 08:32 AM
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Thanks, so if i try and peer down the standpipe and see shiny water back, there must be trap under slab. If dry, no trap, and i guess it uses the utility sink line maybe with a under-slab WYE as a "horizontal wet vent?!" Or it just isn't vented at all and air/water moves in combination with the washing machine discharge.

My main concern adding another p-trap upstairs for the new washing machine is if there is another p-trap it will be flowing into below the slab. Either way i'll be adding a new vent upstairs so that shouldn't be an issue. So if there is a p-trap, i'll probably need to break concrete and replace with an elbow? but if i see dry pipe down there i should be good to go i think?

Still wondering about that floor drain thou, did people pipe those into the septic run with a trap or something? I'm worried about stuff clogging up and backing up through that one day, so maybe it should be capped under the concrete.
Old 01-26-19, 10:25 AM
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If you have access to the septic tank lid (but you might have to dig) you could run red dyed water down the floor drain in the basement and see if you see it in the septic tank.

Just a thought.
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