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Upstairs shower plumbing questions

AcCable's picture


In an 2nd floor bathroom I am trying to separate a tub/shower into a separate shower and free standing tub.  Is it okay to used the same drain that was used for the tub previously which is 1 1/2" ? 

Would there only be a problem if, by chance, the tub was draining at the same time someone was taking a shower? 

The first floor has been remodeled so it will require tearing into some walls to run a new drain. 

It seems that a new 2" drain should be installed for the shower but I don't know if that is going overboard.  I really don't want to have to blow my budget on something that would never be an issue.  


It depends on how much of a (post #214526, reply #1 of 3)

It depends on how much of a code weenie the inspector is.  I can't remember whether a transition to 2" is required when any two large-volume drains meet, or whether it's just when the drains from two different rooms meet.

From a practical standpoint, the danger is that if someone drains the tub while someone else is taking a shower, and the drain is sluggish due to hair buildup, etc, the tub water will rise an inch or two into the shower.  It is unlikely to cause a flood unless the occupants ignore the warning signals and don't get the drain augered when their toes keep getting wet(ter).

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

That is what I was (post #214526, reply #2 of 3)

That is what I was thinking.  Can the transition to the 2" be done in the basement assuming there is access or does it have to be right after the two drains meet?

2" (post #214526, reply #3 of 3)

A shower requires a 2" drain. A shower drain has a 2" fitting. You can't put a 2" fitting into 1 1/2" pipe. This is not an issue of whether you can  put 2  1 1/2" drains into a single pipe (you can). If, somehow, you can find a 1 1/2" shower drain your inspector might buy it.