3 inch to 4 inch waste line

Users who are viewing this thread

Cacher_Chick

Test, Don't Guess!
Messages
5,458
Reaction score
213
Points
63
Location
Land of Cheese
The required pipe size is determined by the number of fixture units draining into the pipe. Most common single-bath, single family homes would not require a 4" drain anywhere. Local plumbing codes may require 4" from the home to the city sewer connection.
 

Gary Swart

In the Trades
Messages
8,101
Reaction score
84
Points
48
Location
Yakima, WA
The way your question is worded, it sounds like you want to reduce the out going drain from 4" to 3". I hope this is how I am reading the question and not what you want to do. (sorry, I'm just an old school teacher)
 

hj

Master Plumber
Messages
33,599
Reaction score
1,037
Points
113
Location
Cave Creek, Arizona
Website
www.terrylove.com
you do not say HOW the problem was solved, but the common answer to the original question would be "you can use 3 inch up to the point where you connect a fourth toilet. Then it has to increase to 4 inch pipe". UNLESS, you live in an area which requires the vent out the roof to be the same size, undimished, as the incoming line, then you need to run 4" all the way.
 

Willie Two

New Member
Messages
36
Reaction score
0
Points
0
Location
British Columbia
The inspector allowed 3 inch as I only have 2 WC. Increase to 4 inch just before it leaves the building.

Most codes allow three toilets on 3"
Where the forth toilet is added, it goes to 4"
Building sewers are 4" regardless.
Added by Terry
 
Last edited by a moderator:

MikePlummer

Plumber
Messages
191
Reaction score
1
Points
18
Location
Ontario, Canada
Website
www.facebook.com
by code you should be 4" building drain to your 3" stack which remains 3" all the way to open air
2 toilets on 3" if horizontal, 4" downstream of 3rd
3" stack can be up to 6 toilets, after six must be 4" pipe
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks