# 2" p-trap gpm



## SPH (Nov 4, 2008)

How many GPM can a 2" p-trap handle. Anyone have any sizing charts on this?


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## PLUMB TIME (Feb 2, 2009)

30 GPM intermittent flow


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## Drumma Plumma (Jun 5, 2012)

PLUMB TIME said:


> 30 GPM intermittent flow


Where did you get that info from?


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## SPH (Nov 4, 2008)

also curious where you got that number from.


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## justme (Jul 4, 2012)

The code book like the IPC or UPC


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## Michaelcookplum (May 1, 2011)

Not true, 13.5 is the answer, if you asking for sizing a trap in a master shower with multiple outlets, 6 or more requires a 3" trap. 2.5gpmx5=12.5


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## plbgbiz (Aug 27, 2010)

What is the GPM discharge rate of the pump on an automatic clothes washer?


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## Michaelcookplum (May 1, 2011)

plbgbiz said:


> What is the GPM discharge rate of the pump on an automatic clothes washer?


That's a great point, I'm sure it's more then 13.5! Probably more like 20 with the modern ones! I'm guessing the modern code has not kept up with technology. Perhaps the minimum stand pipe length has something to do with the formula because by the 2009 IPC, 2" trap can only take 13.5gpm. Atleast that's what the inspector told me in person.....which in reality, unfortunantly, that's what matters


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## SPH (Nov 4, 2008)

So how do we size p-traps? If we know the discharge of a fixture in GPM what is the next step?


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## Michaelcookplum (May 1, 2011)

SPH said:


> So how do we size p-traps? If we know the discharge of a fixture in GPM what is the next step?


Compare it to the charts.....


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## eddiecalder (Jul 15, 2008)

Michaelcookplum said:


> Compare it to the charts.....


Our charts are not in GPM they are in "fixture units"

"A unit of measure based on the rate of discharge, time of operation and frequency of use of a fixture that expresses the hydraulic load that is imposed by that fixture on the drainage system"

GPM is only part of the equation in our code

Is the fixture a "continuous flow" or "semi continuous flow"?

What type of fixture is it?


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## eddiecalder (Jul 15, 2008)

SPH said:


> So how do we size p-traps? If we know the discharge of a fixture in GPM what is the next step?


You have to convert the GPM to liters per second and then convert that to fixture units ( 2.4.10.3 to 2.4.10.5 of the national code )

If you are able to use 2.4.10.3 you size the trap off the branch table 2.4.10.6.b


If you know the fixture units before hand you should be able to use table 2.4.10.2 according to this chart it should be 3 fixture units


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## evan (Dec 10, 2010)

Michaelcookplum said:


> Not true, 13.5 is the answer, if you asking for sizing a trap in a master shower with multiple outlets, 6 or more requires a 3" trap. 2.5gpmx5=12.5


12.3 actually. So any more than four would be violating at 2.5 gpm's per. We've been planning to use a special handheld which flows only 2.0 gpm's if any inspectors bring this up. So far, none have. 

BTW, this master shower http://www.plumbingzone.com/f21/hansgrohe-axor-starck-16564/?highlight=starck has 25 gpms going through one 2" trap on a channel drain. worked just fine


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## rob the plumber (Oct 21, 2011)

I've been hit with this one by Mr plumbing inspector. 4 body sprays, 1 shower head, 1 rain head, 1 hand held. He made use use a 3" trap and strainer. We all know that a 2" strainer takes the water just fine, and luckily this has only happened once to me in 20 years.


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## Michaelcookplum (May 1, 2011)

evan said:


> 12.3 actually. So any more than four would be violating at 2.5 gpm's per. We've been planning to use a special handheld which flows only 2.0 gpm's if any inspectors bring this up. So far, none have.
> 
> BTW, this master shower http://www.plumbingzone.com/f21/hansgrohe-axor-starck-16564/?highlight=starck has 25 gpms going through one 2" trap on a channel drain. worked just fine


Oh you just had to go there, .2.....what's .2! Hahah. I'm just repeating what the ffx co inspector told me


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## Plumberman911 (Dec 23, 2012)

rob the plumber said:


> I've been hit with this one by Mr plumbing inspector. 4 body sprays, 1 shower head, 1 rain head, 1 hand held. He made use use a 3" trap and strainer. We all know that a 2" strainer takes the water just fine, and luckily this has only happened once to me in 20 years.


UPC 2009 has a chart for figure ing the size drain needed. You can have five heads on a 2" trap. We always said five valves. But then you have to factor body sprays. So safe bet is figure heads

Sent from my iPhone using PlumbingZone


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## Michaelcookplum (May 1, 2011)

A different inspector told me today the 2009 IPC is 12.4 gpm


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## Protech (Sep 22, 2008)

Michaelcookplum said:


> That's a great point, I'm sure it's more then 13.5! Probably more like 20 with the modern ones! I'm guessing the modern code has not kept up with technology. Perhaps the minimum stand pipe length has something to do with the formula because by the 2009 IPC, 2" trap can only take 13.5gpm. Atleast that's what the inspector told me in person.....which in reality, unfortunantly, that's what matters


The non-high efficiency units put out more than 20gpm.


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## justme (Jul 4, 2012)

I know what the code says, but a 2" trap can handle 30 gpm. They size drains for a little over a third of what they can actually handle. But the code is what we have to abide by .


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## evan (Dec 10, 2010)

Michaelcookplum said:


> A different inspector told me today the 2009 IPC is 12.4 gpm


did you whip out your code book that you keep in your van and set him straight? :thumbsup:


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