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# Thread: size of shower drain pipe

1. ## size of shower drain pipe

We are putting in a new master bedroom and bath and I have a question about shower drain size. Our shower will be 3' 4" by 5' 9" and it will have 3 shower heads hooked up to a 3/4" thermostatic valve: one regular head, one handheld on a bar on the opposite wall, and a rain-type head on the long wall. The two regular heads are rated at 2.5 GPM but can go up to 5 GPM with the flow restrictor removed. The rain-type head will do 6 GPM at 45 PSI. The only time more than one shower would be going at any one time would be if one of us uses the regular shower head and the other uses the handheld. Is a 2" diameter drain pipe adequate? Our plumber has just roughed in a 2" drain but I am concerned since a few people have mentioned that in their spa-type showers they don't get adequate drainage (I don't know the details of their setup, but I would imagine they wouldn't be less than 2" since they are new).

2. As long as it is properly vented 2" is suffice for a shower.

3. Thanks. So that means a 2" pipe is capable of draining at a rate of 10 GPM--is there any way to look that sort of thing up?

4. Well, think of it this way - what size pipe are you using to supply the shower? the area of the drain is quite a bit bigger than that supply (pi r^2 say 3/4" supply = 0.44sq in vs 3.14sq in)...yes, there is a pressure difference, but gravity does work to speed it along.

5. Jim,
Although the size of the shower pipe might have a small effect on the pressure drop, it doesn't have a big effect on the volume of water delivered, and it's that flow that counts. I just want to know if I'll be standing in a lot of water if I run 6-10 gallons/min.
Rob

6. Originally Posted by RBKM
Jim,
Although the size of the shower pipe might have a small effect on the pressure drop, it doesn't have a big effect on the volume of water delivered, and it's that flow that counts. I just want to know if I'll be standing in a lot of water if I run 6-10 gallons/min.
Rob

whats your options? 3"? i checked charlotte pipe and a 3" solvent weld p-trap is approx. 12" tall. unless you are in a slab it would be tough to fit.

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