Right? Wrong? Why was this done?

[Ace Sewer]

Never saw this before and was wondering if it was just odd, or if there is some reason for it.

Multi-unit building, smell problem and toilets acting funny. Turned out to be a main line clog that had been there a while... sewage a foot deep in places in crawlspace. Hubbed cast iron drain line. Uphill end of line continues a few feet above last place where anything else drops in and terminates in a trap with nothing attached to it, top of trap open, no way there was anything ever in that location to be attached to it. Sewage backing up out of open trap because of blockage lower down.

In a way it was good as nothing backed up into the units and I could be as messy as I wanted as a few more gallons sure wans't going to make it any worse. But it was bad as the building put a few hundred gallons of nasty in the crawlspace before anyone decided to have a look.

Is this commonly done? Why?

[Masterplumb]

Around here it is code to have a house trap. They are supposed to be capped at the clean outs. Someone probably removed the caps so that IF a stoppage occured it would back up into the crawl space and not the lowest unit.

[Ace Sewer]

The house trap traps the main line though...right? It is in line at the low end and all the wastewater flows through it, yes? This was not that. This was on the UPHILL end of the line, above all fixtures, where I commonly see a cleanout plug. Nothing would ever flow through it unless the line backs up...

[Masterplumb]

The house trap traps the main line though...right? It is in line at the low end and all the wastewater flows through it, yes? This was not that. This was on the UPHILL end of the line, above all fixtures, where I commonly see a cleanout plug. Nothing would ever flow through it unless the line backs up...

Ok, I just re-read your o.p. and think I understand now. Could it have been a seperate main line trap maybe for roof drain(s)/leaders that tied into the sanitary????

Also around here some municipalities make us put a seperate house trap for sewage ejector pumps. Could it have been for an old bathroom below the sewer line????

[djrenek1]

i agree sounds like unfinshed storm water drain trap or something

[mtnman1100]

Or maybe it was a Friday after a six pack lunch.

[SlimTim]

It seems like there would have been a constant odor from sewer gas before the stoppage. That trap surely had dried out.