3" Or 4" ?

Celtic

Which is "better" for a typical SFH's closet flange to the main DWV?

In talking with a local plumbing inspector, he offered his "opinion"....I now ask the pros for their opinions.

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BCConstruction

In the UK we was always told to use no less than 4" soil pipe but i see a lot of 3" over here and it seems to do the job. Esp now that the toilets are using a lot less water to flush. But i do notice the toilets over here block up a lot more than in the UK.

Ron The Plumber

SFH's?

Celtic

Single
Family
Home
s

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Ron The Plumber

3" Always

Celtic

Why?

I generally see 4" cast with lead elbows all over.

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Ron The Plumber

For new installs 3" ABS or PVC.

Celtic

...why not 4" ABS or PVC?

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Ron The Plumber

Why run 4" when code allows 3" for up to 3 toilet till you need to be 4", cost less to run 3" then 4"

Celtic

...because that doesn't really answer the question:

Cheaper is not always "better".
Bare code minimum is not always "better".

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Ron The Plumber

Sorry you can't accept my answer I shall bow out.

Celtic

It's not the I can't accept your answer....I just won't accept it w/o some theory or logic behind it.
Simply because "it's code" doesn't sit well with me.

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Ron The Plumber

Waste water flows just a well inside 3" as it does inside 4", that sounds logical to me.

CookeCarpentry

It's not based on number of toilets, but quantity and size of meals. Do you attend a lot of all-u-can-eat buffets? Fast food? Corn?

Better opt for the 4" to be on the safe side.

TimelessQuality

I'm not a plumber, but I have stayed at Holiday Inn, and used a lot of toilets....


Given the same toilet, 3" will have a faster flow than 4"...

Gets 'stuff' movin down the line

What is larger than 3" that will go through the trap in the WC?

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-Steve

"The most beautiful thing we can experience is the mysterious. It is the source of all true art and science." ~ Albert Einstein

Plumber_Bill

DFU's Drainage fixture units goveren the piping size.

Read the code book! Usually on residential work the I.P.C. will allow 2 bathroom groups on 3" PVC/ABS, No/Hub cast iron, copper tube. More fixtures (ie: another powder room or a mud bath) the the piping from that point of connection to the main must be 4" to the exit from the building. Usually 4" is required for the house sewer at least in the code we follow.

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This and That

protechplumbing

To the OP:

3" lateral drain with 4" riser is the best.

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Plumber, Repiping, Replumbing, Leak Detection, Solar Water Heater, Polk County Plumber, Lakeland Plumber, Winter Haven Plumber

Celtic

<~~~~ Look at my "trade".

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Patrick

just make sure the pipe dumps into your neighbors pond

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Originally Posted by Celtic
Like I said...I'm sure you are very good at what you do ~ whatever that is and where ever it happens.

Celtic

In case you missed it, I'm not interested in what the book says....I'm interested in the theory behind it.

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