tub shower combination - drain size

[shaken-n-stirred]

It seems like most tub shower combination units have 1 1/2 inch traps and 1 1.2 inch horizontal drain lines. Correct? Wrong?

However, the codes seems to state that a 1 1/2 inch drain is only good for ONE FIXTURE UNIT and a tub shower combination is TWO units.

So do I need a 2 inch drain?

If so, can I come down from the water and overflow, into a 1 1/2 inch trap and then step the drain line up at that point?

Confused.

Thanks

 

[frodo]

showers require a 2'' trap and arm
tub/shower require a minimum 1.5 trap / arm

that is the minimum...I personally will not run a 1.5 arm on a tub/shower

never have never will, hey clog with soap and hair to easy

 

[frodo]

you use a 2'' ptrap with a 2x 1.5 bushing in the trap, making the stand pipe 1.2''

 

[shaken-n-stirred]

you mean 1 1/2 inch stand pipe? Not 1.2? And by stand pipe do you mean the length of pipe between the sanitee on the waste and overflow and the trap?

thanks

 

[frodo]

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