Im trying to understand how this works.

Theres a 3" main vent that goes out the roof and drops to the basement where its connected to a 3' horizontal lateral. Theres 2 toilets that connect to this horizontal portion. There is also a 1.5" connection for a bathtub to one of the hubs on the lateral. There is also another 1.5" connection for a kitchen sink.

The kitchen sink has its own 1.5" vent.

However, the bathtub does not have a separate vent.

So my question....


is the bathtub vented thru that main 3" vent? The entry point at the hub for the tub is about 3' away from where the 90 is for the vent that then goes horizontal.

that depends on what else that 3 inch stack is serving.

that main stack does not serve any other fixtures.

without seeing or knowing more about the tub connection, we cannot tell if it is vented, or if it is vented properly.

Hello-

What other information do I need to provide?

and/or is it generally acceptable for a tub to be vented thru the main stack or do they generally need their own roof vent like a sink might have?



thank you.

the tub can be 'stack vented' if it is close enough but no toilet drain can be between the tub and the stack vent. a kitchen sink or a lav can enter the stack above the tub and not affect the 'stack vent'. neither the kitchen nor the lav need be individually vented if they are close enough to the stack.

the toilet is between the vent and the tub. This is all on one level.

This is 1950's setup.... was this against code at the time?... how big of an issue do I have here?

Does adding an AAV on the drain to the tub (between the trap and the hub on the lateral) correct the situation?





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Are you experiencing a problem?

No problem that I can see.... Is this something you would leave in place if it seems functional?



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if it has been functioning without issues since harry truman was president, i would leave it as is.

That's what I usually say...

but I wanted to understand why its wrong, what symptoms might occur and if a studor vent on the tub line (between the trap and the hub) is a suitable fix.

I do assume its the original design... other than PVC on the tub drain line which connects to the cast iron lateral with a shielded hub coupling.

but I will confirm, Harry Truman did not take a bath here!

How and where it connects to the main line determines whether it needs its own vent, and we co not have that information.

It is wrong in a theoretical sense, (since codes are concerned about what COULD happen), but may NOT necessarily cause YOU problems. It has NEVER been an approved way to connect the tub to the main line.



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thanks guys.

What is it that "could happen" as HJ put it....

also is a studor vent between the trap and the entrance to the main a suitable fix?

Where its been like this since Eisenhower, its new to me as I have only been here since Obama second term. So I don't know its track record.



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If the stack backed up, it would siphon the water from the tub trap when it drained. If you weren't home, that could let untold potential flies and bugs up through your tub vent, seeking the nice inside of your home where they smell food.

Theoretically, the waterfrom the toilet flowing past the tub drain could siphon the trap, is one "possibility".