Undersized waste line

motomars

Previous owners of my house connected a 3"pvc bathroom waste line to a smaller - about 2.5"od - cast iron pipe. The connection is just above the slab in the basement and the cast iron section has one 45 degree turn and runs about 6' before connecting to the main sewer line. How concerned should I be about this?

I don't know if waste "thins" as it travels through the pipe, but fwiw, the bathroom is on the 2nd floor and the PVC runs about 30' before connecting to the cast iron. Also, there's a cleanout where the two connect.

As I see it the options are: dig up the floor and replace the cast iron (not eager to do that, as it means demo'ing a section of finished floor…); dig up the area around the elbow and just replace that, so at least the turn is 3" (would this make enough of a difference to be worth it?); or, leave it be and use the clean out to snake the cast iron section every so often. Thanks in advance for any input.

Mad Dog_2

Wait till it backs up..Mad Dog

mattmia2

How did this happen in the first place? Was a bathroom added where there was none before?

Larry Weingarten

A question. Is there any other place you can tie into 3" pipe? 🤔

Yours, Larry

delcrossv

Tied a waste line onto a vent or sink drain? That's a no-no.

Try a wait and see, but it will eventually clog. N.B. @Mad Dog_2 's comment above. Not. Fun.😬

motomars

They added a full bathroom in the front of the house where there used to only be sink - it's an old rowhouse and the main stack is in the back. There's no easy way to tie this line into the stack.

If I dig up the cast iron elbow and replace it with 3" pvc, would that help? Or not worth the effort?

I may replace the basement floor in the next few years, and could dig up up the cast iron pipe then. So this doesn't necessarily need to be a forever solution.

Larry Weingarten

Hi, Maybe the right balance is simply to have some good drain cleaning tools around… at least until you can fix the pipe properly.

Yours, Larry

hot_rod

sounds like they tied into a 2” drain or vent pipe?

Is it clogging up, or why the concern? It needs to be 3” for a toilet, by code.

mattmia2

Can you run it along the ceiling or the permitter of the basement to get to the main stack?

delcrossv

https://forum.heatinghelp.com/discussion/comment/1855479#Comment_1855479

Not worth the effort unless it changes to something bigger under the floor. If not, might as well run 3" all the way to the sewer.

To @mattmia 's suggestion, how far to the stack? That bathroom needs to be vented somewhere.

Alan (California Radiant) Forbes

There's a 2" discharge on sewer ejectors, but that after it's been Osterized.

You could put a 3" cleanout just before it transitions to 2" and eat lots of veggies.