water closet dfu - Plumbing Zone

smellslike$tome · 03-22-2010, 08:55 PM

Another thread got me looking at dfu's vs. pipe diameter. I was all set to blast away at 2.5" pipe serving a wc but woops, it's rated at 4 dfu. I'm looking at the 2009 IPC which I just received the other day and what struck me is the fact that they have a private, 1.6 gpm wc rated at 3 dfu. I never remember wc ever being less than 4 except if included as part of a bathroom group, the bathroom group was rated at 6 dfu. So anyway, if a private, 1.6 gpm wc is rated at 3 dfu then according to the chart (709.2 IPC) "Drainage Fixture Units For Fixture Drains Or Traps", then technically, a wc could be served by a 2" drain which of course is utterly ridiculous. So I started looking for the part that said that this did not apply to wc which required a minimum 3" drain, only I can't find it.

Anybody know where it is or is this just a major flub in the 2009 IPC?

plumbpro · 03-22-2010, 09:02 PM

botom of the chart 710.1(1) note a

smellslike$tome · 03-22-2010, 09:15 PM

I knew it was in there somewhere.

Thanks.

Now, does anybody remember any wc ever being 3 dfu before? Maybe it was before but I sure as heck do not remember it.

plumbpro · 03-22-2010, 09:19 PM

I would have to look around for my old code book, but I think that the 03 IPC was at 4 dfu, the new IPC has it at 3dfu for 1.6gpf/private and 5 dfu for a bathroom group w/ 1.6 private

AKdaplumba · 03-22-2010, 11:54 PM

Doesnt it say a wc has to be min 3"

plumbpro · 03-23-2010, 12:03 AM

yeah, min 3" per the chart I noted in the 2 post up there

Tommy plumber · 08-19-2010, 05:26 PM

My old '94 code book lists DFU for W/C,

Water closet, flushometer tank, public or private 3 DFU
Water closet, private installation 4 DFU
Water closet, public installation 6 DFU

a4daddywagon · 09-11-2010, 03:27 PM

The code also states that waste piping can't be reduced in size from a fixture outlet (even if a smaller pipe meets the DFU rating) as this would cause a high potential for blockage.

plumbpro · 09-11-2010, 03:39 PM

Quote:

Originally Posted by a4daddywagon

The code also states that waste piping can't be reduced in size from a fixture outlet (even if a smaller pipe meets the DFU rating) as this would cause a high potential for blockage.

Except a 3x4 wc 90-this is not considered a reduction in size.

03-22-2010, 08:55 PM	#1
smellslike$tome residential service Join Date: Jun 2008 Location: Birmingham, AL Posts: 1,809 My Photos	water closet dfu Another thread got me looking at dfu's vs. pipe diameter. I was all set to blast away at 2.5" pipe serving a wc but woops, it's rated at 4 dfu. I'm looking at the 2009 IPC which I just received the other day and what struck me is the fact that they have a private, 1.6 gpm wc rated at 3 dfu. I never remember wc ever being less than 4 except if included as part of a bathroom group, the bathroom group was rated at 6 dfu. So anyway, if a private, 1.6 gpm wc is rated at 3 dfu then according to the chart (709.2 IPC) "Drainage Fixture Units For Fixture Drains Or Traps", then technically, a wc could be served by a 2" drain which of course is utterly ridiculous. So I started looking for the part that said that this did not apply to wc which required a minimum 3" drain, only I can't find it. Anybody know where it is or is this just a major flub in the 2009 IPC?

08-19-2010, 05:26 PM	#7
Tommy plumber Senior Member Join Date: Feb 2010 Location: South Florida Posts: 4,140 My Photos	1994 Standard Plumbing Code SBCCI My old '94 code book lists DFU for W/C, Water closet, flushometer tank, public or private 3 DFU Water closet, private installation 4 DFU Water closet, public installation 6 DFU __________________ Hire a licensed master plumber.

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03-22-2010, 09:02 PM	#2
plumbpro Senior Member Join Date: Mar 2010 Location: NE Arakansas Posts: 1,162 My Photos	botom of the chart 710.1(1) note a

03-22-2010, 09:15 PM	#3
smellslike$tome residential service Join Date: Jun 2008 Location: Birmingham, AL Posts: 1,809 My Photos	I knew it was in there somewhere. Thanks. Now, does anybody remember any wc ever being 3 dfu before? Maybe it was before but I sure as heck do not remember it.

03-22-2010, 09:19 PM	#4
plumbpro Senior Member Join Date: Mar 2010 Location: NE Arakansas Posts: 1,162 My Photos	I would have to look around for my old code book, but I think that the 03 IPC was at 4 dfu, the new IPC has it at 3dfu for 1.6gpf/private and 5 dfu for a bathroom group w/ 1.6 private

03-22-2010, 11:54 PM	#5
AKdaplumba Senior Member Join Date: Jan 2010 Location: Vancouver BC Posts: 723 My Photos	Doesnt it say a wc has to be min 3"

03-23-2010, 12:03 AM	#6
plumbpro Senior Member Join Date: Mar 2010 Location: NE Arakansas Posts: 1,162 My Photos	yeah, min 3" per the chart I noted in the 2 post up there

09-11-2010, 03:27 PM	#8
a4daddywagon Junior Member Join Date: Sep 2010 Posts: 3 My Photos	The code also states that waste piping can't be reduced in size from a fixture outlet (even if a smaller pipe meets the DFU rating) as this would cause a high potential for blockage.