I am in the process of installing a new custom shower in my master bath. I will have multiple shower heads with body sprays.

My questions are:
How gallons per minutes can my 2" drain pipe handle?
I heard that I can put in two drain to increase the rate of flow, is that true?
And if I put in two drains do I need two trap or can I join the two drain into one trap?

Thanks,
dekelemx

Quote:

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Originally Posted by dekelemx

I am in the process of installing a new custom shower in my master bath. I will have multiple shower heads with body sprays.

My questions are:
How gallons per minutes can my 2" drain pipe handle?
I heard that I can put in two drain to increase the rate of flow, is that true?
And if I put in two drains do I need two trap or can I join the two drain into one trap?

Thanks,
dekelemx

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A 2" trap can handle in excess of 20gpm.

You can join 2 shower drains into a single 2" trap with a continuous waste, but I wouldn't recommend doing so.

I've plumbed numerous showers with multiple thermostatic valves individually supplying body sprays, conventional shower heads, hand held showers and overhead 'rain-head' shower heads -- And have never had a problem with a 2" trap keeping up with the simultaneous operation of all of the valves.

Is 20 GPM the rate for 2" pipe and will it be restricted with the drain grate on top?
Is there a 3" drain for tile aplications?
I just don't want to build this great shower and stand in standing water because it doesn't drain quick enough. 3" will provide more drain area than a 2" drain if it is available.

Quote:

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Originally Posted by dekelemx

Is 20 GPM the rate for 2" pipe and will it be restricted with the drain grate on top?
Is there a 3" drain for tile aplications?
I just don't want to build this great shower and stand in standing water because it doesn't drain quick enough. 3" will provide more drain area than a 2" drain if it is available.

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20GPM is the rating for the trap, trap arm and drain -- And I don't see the drain grate being a problem.

There are 3" drains available in both plastic and cast iron, but you will need to provide a 3" trap, trap arm, drain and a 2" vent for the drain to operate as intended, as well as to pass inspection -- And if the master bath is above a living space, you will need to factor in that a 3" p-trap with the 2" vent rolled horizontally above the centerline of the 3" inch drain and sloped upwards 1/4" per foot is not going to fit inside of a conventional joist bay.

Really, a properly roughed-in 2" drain keeping up with 3 or 4 thermostatic shower valves running simultaneously is not going to be a problem.