# Tile shower drain size for custom shower.



## Plumber Mark (Mar 14, 2014)

Looking for some advice. Plumbing a new house with a tile shower. Normally I put in a 2" tile drain, but homeowner wants 3 body [email protected], 2 handheld showers @2.5gpm, and one shower [email protected] for total of 13.5gpm. Will I need a 3" drain to handle this volume of water? What is max gpm on a 2" drain? Never done a shower with this much going on! Not sure I have room for 3" drain as shower is recessed in floor and trusses are smaller! Thanks


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## Tommy plumber (Feb 19, 2010)

Check the code book on that one. It'll give you a table with the GPM with the dfu chart. Or run it by an inspector.


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## Gargalaxy (Aug 14, 2013)

Table 709.1 in Florida code book..... in shower: greater than 12.3 to 25.8 gpm, dfu 5, minimum size of trap 3".


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## Plumber Mark (Mar 14, 2014)

Minnesota code we can have 6 Dfu on a 2" horizontal drain line. A domestic shower counts as 2 fixture units minimum 1 1/2" trap size. A shower( gang) 1 fixture unit per head. So if I sized off 1 Dfu per head I would be at 6dfu which we can have on a 2" horizontal drain. I have never needed bigger than a 2" drain in a residential shower, but I have never had more than 2 heads and a few body sprays. The show room consultant at Ferguson suggests a 3" drain, just not sure I have room for it!


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## Plumber Mark (Mar 14, 2014)

Also in the definition section of my code book a drainage fixture unit is a common measure of the probable discharge into the drainage system by various types of plumbing fixtures on the basis of one d.f.u. Being equal to 7.5 gallons per minute discharge.


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## SchmitzPlumbing (May 5, 2014)

it depends on the valve. are you doing a 3 way diverter valve or volume controls. 3 ways, all heads dont perform at once. volume , full volume, all at once. what size piping are you feeding it with? if its only 3/4 copper, the drain is the least of your future problems. more questions than answers


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## supakingDFW (Aug 19, 2014)

Sounds like with everything they are wanting installed, you'll need another shower valve if they plan on wanting to operate those simultaneously, which will likely need a 3" drain... When you're figuring up those fixture units, it's based off of the number of valves because each valve has a certain flow rate no matter how many heads you divert it to.


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## Plumber Mark (Mar 14, 2014)

Yes I probably need a 3" drain looks like they are going with a Kohler custom shower bundle K693-k-na. Putting in 2 of these, one will have a standard shower head and a handheld and the other will have 3 body sprays and a handheld. I guessing I will need to run one inch supply piping to shower to get enough water?


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## david perkins (Sep 27, 2014)

A few things should always be kept in mind while plumbing in your home. To prevent pipes from freezing you should maintain a constant temperature in your home above freezing. Your pipes can freeze if the air around it is below freezing.**spammer's link removed** should always be taken by a licensed and experienced plumbers.


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## Michaelcookplum (May 1, 2011)

Plumber Mark said:


> Yes I probably need a 3" drain looks like they are going with a Kohler custom shower bundle K693-k-na. Putting in 2 of these, one will have a standard shower head and a handheld and the other will have 3 body sprays and a handheld. I guessing I will need to run one inch supply piping to shower to get enough water?


Why not just put two two" traps and two drains? I've never done it before cause Ive always had room for a three inch trap but inspector told me when I asked your same question that I had to have one three inch trap and drain or two two inch traps and drains. Might not be best looking or easy for tile guy but if you don't have room for three inch trap it's another option.


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## SchmitzPlumbing (May 5, 2014)

david perkins said:


> A few things should always be kept in mind while plumbing in your home. To prevent pipes from freezing you should maintain a constant temperature in your home above freezing. Your pipes can freeze if the air around it is below freezing. **spammer's link removed** should always be taken by a licensed and experienced plumbers.


 thanks a lot doctor obvious.:blink:


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## Coolcanuck (Jan 30, 2012)

david perkins said:


> A few things should always be kept in mind while plumbing in your home. To prevent pipes from freezing you should maintain a constant temperature in your home above freezing. Your pipes can freeze if the air around it is below freezing. **spammer's link removed** should always be taken by a licensed and experienced plumbers.


 A plumber is born every minute


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## 504Plumber (Jan 26, 2011)

Try to find out if they're using kerdi or not, unless they make one now the kerdi system doesn't have a 3" strainer. A couple years back we put a 3" trap and a 3" clamp and ring, the tile guys tried to use it with a kerdi floor and they ended up having to rip it out. 

IMHO I think the 2" would be fine, the odds are slim they are going to have everything running. More likely than not it will be a shower head and body sprays. After the novelty of the body sprays wear off they will never be used again.


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## Dpeckplb (Sep 20, 2013)

Here it would have to be 3".


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## sparky (Jan 8, 2014)

What I would do is one 2"p-trap with a 2"drain,and above the trap put in a 2" indirect drain with no trap to help catch any excess water that the drain can't carry!!


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## plbgbiz (Aug 27, 2010)

sparky said:


> What I would do is one 2"p-trap with a 2"drain,and above the trap put in a 2" indirect drain with no trap to help catch any excess water that the drain can't carry!!


Could you say that again...but slower? :blink:

Maybe a drawing to go with it.


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## budders (May 19, 2013)

What about a small troth drain on the lip of the tile shower and pitch it to that?


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## plbgbiz (Aug 27, 2010)

Changing the style and/or quantity of receptors will not change the capacity of the fixture drain pipe size.


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## Coolcanuck (Jan 30, 2012)

budders said:


> What about a small troth drain on the lip of the tile shower and pitch it to that?


2 traps in it


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## supakingDFW (Aug 19, 2014)

plbgbiz said:


> Changing the style and/or quantity of receptors will not change the capacity of the fixture drain pipe size.


Ezzactly...


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## SchmitzPlumbing (May 5, 2014)

why worry about the drain. do you have a 120 gallon water heater? i doubt it. at the most, you probably have a 75 gallon. 13.5 gpm equals a, at most, 5 minute shower. the drain will catch up. the shower drain strainer doesnt allow for full flow of the drain. everyone is over thinking it. it is a shower. showers require a 2" drain.


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## sparky (Jan 8, 2014)

sparky said:


> What I would do is one 2"p-trap with a 2"drain,and above the trap put in a 2" indirect drain with no trap to help catch any excess water that the drain can't carry!!


If the water is coming out faster than the 2"grate can take it then it could spill over into the indirect drain,a 2" pipe will take anything a shower can rain down on it,hell we are allowed to put 3 washers on a 2" line and it takes it perfect,so I know a 2" drain pipe will take what this shower can rain down on it,with the indirect waste pipe it could take anything that the grate can't handle


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## sparky (Jan 8, 2014)

SchmitzPlumbing said:


> why worry about the drain. do you have a 120 gallon water heater? i doubt it. at the most, you probably have a 75 gallon. 13.5 gpm equals a, at most, 5 minute shower. the drain will catch up. the shower drain strainer doesnt allow for full flow of the drain. everyone is over thinking it. it is a shower. showers require a 2" drain.


Zactly,well said


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## plumbdrum (Nov 30, 2013)

sparky said:


> Zactly,well said


You gentlemen clearly don't comprehend what DFU is.

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## budders (May 19, 2013)

SchmitzPlumbing said:


> why worry about the drain. do you have a 120 gallon water heater? i doubt it. at the most, you probably have a 75 gallon. 13.5 gpm equals a, at most, 5 minute shower. the drain will catch up. the shower drain strainer doesnt allow for full flow of the drain. everyone is over thinking it. it is a shower. showers require a 2" drain.


 what if it is off a tankless coil? Then its unlimited hot water


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## sparky (Jan 8, 2014)

plumbdrum said:


> You gentlemen clearly don't comprehend what DFU is.
> 
> Sent from my iPhone using PlumbingZone


i know preciously what dfus are,learned it about 22yrs ago,some users on this site will make a moutain out of a mole hill,i guaranttee you that a 2" pipe would more than handle the water in the above shower installed the way i described:yes:


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## plumbdrum (Nov 30, 2013)

sparky said:


> i know preciously what dfus are,learned it about 22yrs ago,some users on this site will make a moutain out of a mole hill,i guaranttee you that a 2" pipe would more than handle the water in the above shower installed the way i described:yes:


Still doesn't mean it's right does it? You took a test based on the code you use, got a license in whatever state your in, adhere to whatever code you work with.

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## Michaelcookplum (May 1, 2011)

sparky said:


> i know preciously what dfus are,learned it about 22yrs ago,some users on this site will make a moutain out of a mole hill,i guaranttee you that a 2" pipe would more than handle the water in the above shower installed the way i described:yes:


I'd like to be a fly on the wall when you argue that to an inspector


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## Michaelcookplum (May 1, 2011)

sparky said:


> i know preciously what dfus are,learned it about 22yrs ago,some users on this site will make a moutain out of a mole hill,i guaranttee you that a 2" pipe would more than handle the water in the above shower installed the way i described:yes:


I know a wet vent will work but that doesn't mean it's legal everywhere


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## SchmitzPlumbing (May 5, 2014)

plumbdrum said:


> Still doesn't mean it's right does it? You took a test based on the code you use, got a license in whatever state your in, adhere to whatever code you work with.
> 
> Sent from my iPhone using PlumbingZone


according to the code that i have to use, a residential shower stall is 2 dfu. the trap size minimum diameter is 2". a shower is a shower. a tub is a tub.a tub has a 1 1/2" drain. a tub with a 3/4" high flow tub spout is still a bath tub and still requires an 1 1/2 drain. if i have 50 gallons per minute flowing into the tub, what size drain should that be? you are still over thinking it. the strainer is still impeding the flow down the drain. i think that a 2",3" or 4" shower drain will not allow 20 gallons a minute through it, but i have been wrong before!


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## plumbdrum (Nov 30, 2013)

SchmitzPlumbing said:


> according to the code that i have to use, a residential shower stall is 2 dfu. the trap size minimum diameter is 2". a shower is a shower. a tub is a tub.a tub has a 1 1/2" drain. a tub with a 3/4" high flow tub spout is still a bath tub and still requires an 1 1/2 drain. if i have 50 gallons per minute flowing into the tub, what size drain should that be? you are still over thinking it. the strainer is still impeding the flow down the drain. i think that a 2",3" or 4" shower drain will not allow 20 gallons a minute through it, but i have been wrong before!


That's fine if your running a single shower head, you ad multiple heads you add up your DFU based on the amount of heads you have..

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## tim666 (Mar 11, 2014)

Even though it is still passing through a single shower valve?


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## supakingDFW (Aug 19, 2014)

tim666 said:


> Even though it is still passing through a single shower valve?


That's the key question that causes alot of confusion...The DFU's for a shower are calculated based on a single shower valve. That single valve only has a certain flow rate. It doesn't matter if you divert that into 20 different shower heads, still has the same flow rate, therefore the same drain requirement. If you start adding multiple shower valves that could be running simultaneously with other valves, then your flow rate for that shower just increased, and the your DFU's just increased as well. You would have to calculate your DFU's based on the amount of shower valves, not shower heads or other outlets (body sprays, rain heads ect.)


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## sparky (Jan 8, 2014)

Michaelcookplum said:


> I'd likewhy to be a fly on the wall when you argue that to an inspector


Why??he would say looks good:thumbup:


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## sparky (Jan 8, 2014)

supakingDFW said:


> That's the key question that causes alot of confusion...The DFU's for a shower are calculated based on a single shower valve. That single valve only has a certain flow rate. It doesn't matter if you divert that into 20 different shower heads, still has the same flow rate, therefore the same drain requirement. If you start adding multiple shower valves that could be running simultaneously with other valves, then your flow rate for that shower just increased, and the your DFU's just increased as well. You would have to calculate your DFU's based on the amount of shower valves, not shower heads or other outlets (body sprays, rain heads ect.)


Zactly:thumbsup:


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## supakingDFW (Aug 19, 2014)

sparky said:


> Zactly:thumbsup:


AHHHHH!!!....post #666


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## sparky (Jan 8, 2014)

supakingDFW said:


> AHHHHH!!!....post #666


Ohhhhhhhhhhh lol


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## plumbdrum (Nov 30, 2013)

supakingDFW said:


> That's the key question that causes alot of confusion...The DFU's for a shower are calculated based on a single shower valve. That single valve only has a certain flow rate. It doesn't matter if you divert that into 20 different shower heads, still has the same flow rate, therefore the same drain requirement. If you start adding multiple shower valves that could be running simultaneously with other valves, then your flow rate for that shower just increased, and the your DFU's just increased as well. You would have to calculate your DFU's based on the amount of shower valves, not shower heads or other outlets (body sprays, rain heads ect.)


While I'll agree with your statement, my plumbing board does not , and that's what I have to enforce.

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## SchmitzPlumbing (May 5, 2014)

i worked at a 4000 sq foot house today, built in 1910. all origional including the plumbing. i am guesing the plumbing is from the 20s. upstairs shower has a head and 3 body sprays. 1 1/2 drain. never had a problem or a leak from what i can see. all fancy origional ceilings below it on first floor. ps, i didnt get 2 of the old kohler lav faucets fixed or one of the old toilets. house got foreclosed and froze.


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## srloren (Nov 19, 2014)

SchmitzPlumbing said:


> according to the code that i have to use, a residential shower stall is 2 dfu. the trap size minimum diameter is 2". a shower is a shower. a tub is a tub.a tub has a 1 1/2" drain. a tub with a 3/4" high flow tub spout is still a bath tub and still requires an 1 1/2 drain. if i have 50 gallons per minute flowing into the tub, what size drain should that be? you are still over thinking it. the strainer is still impeding the flow down the drain. i think that a 2",3" or 4" shower drain will not allow 20 gallons a minute through it, but i have been wrong before!


A 4" Drain will handle 90 2 unit fixtures all draining horizontally at the same time asl long as you have 1/4" slope. According to the UPC Table.


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## mccmech (Jul 6, 2011)

srloren said:


> A 4" Drain will handle 90 2 unit fixtures all draining horizontally at the same time asl long as you have 1/4" slope. According to the UPC Table.


Who the heck is installing a 4" drain to a shower in residential application?!!!!


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## rjbphd (Feb 5, 2010)

mccmech said:


> Who the heck is installing a 4" drain to a shower in residential application?!!!!


According to this backazzward code.. all plumbing waste underground shall be 4".. some area, must be cast iron..


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## moonapprentice (Aug 23, 2012)

plumbdrum said:


> That's fine if your running a single shower head, you ad multiple heads you add up your DFU based on the amount of heads you have..
> 
> Sent from my iPhone using PlumbingZone


One shower valve, with 6 shower heads. Better up size the shower drain because the "code" book says so!!! Ahahaha


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## plumbdrum (Nov 30, 2013)

moonapprentice said:


> One shower valve, with 6 shower heads. Better up size the shower drain because the "code" book says so!!! Ahahaha



Yup


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## SchmitzPlumbing (May 5, 2014)

if i remember right, my original point was that whatever size drain you install, the strainer will not allow the same gpm as an open pipe.


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## plumber11928 (Feb 18, 2015)

Code Section: TABLE 11.4.1 DRAINAGE FIXTURE UNIT (DFU) VALUES
Under INDIVIDUAL DWELLING UNITS
Shower Stall, 1-1/2" Trap, single 2.5 GPM shower head = 2 DFU
Shower Stall, 2" Trap, multiple shower heads up to 5 GPM total = 2 DFU 3 DFU
Shower Stall, 3" Trap, multiple shower heads up to 10 GPM total = 5 DFU
Shower Stall, 4" Trap, multiple shower heads up to 15 GPM total = 6 DFU

I just completed my 5 hr continuing education class. This is the proposed code change
for the new 2015 NSPC code book. New Jersey


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