New Construction Drain Lines - Plumbing - DIY Home Improvement | DIYChatroom

Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Plumbing


Thread Tools Display Modes
Old 12-03-2009, 01:12 PM   #1
Join Date: Dec 2009
Posts: 1
Rewards Points: 10

New Construction drain lines

Trying to build a house and decided to do my own rough in plumbing in the slab. I know the slope is 1/4" per foot but not sure how to run lines to the main plumbing drain. A 5 ft run from a toilet to the main line which runs down the middle of the house has a debt of 1 and 1/4". A 20' run from a toilet or shower would have a 5" drop. Obviously these two lines would splice into the main line at different debts. Can someone enlighten me on this? And, its a 2 and 1/2 bath house. 3" or 4" main septic line? Thanks very much.


ted03276 is offline   Reply With Quote
Old 12-03-2009, 04:44 PM   #2
An old Tradesmen
Join Date: Oct 2008
Location: Somewhere
Posts: 34,604
Rewards Points: 8,194

Moved to plumbing forum. This is a better forum for this type of question.


beenthere is online now   Reply With Quote
Old 12-03-2009, 08:31 PM   #3
Registered User
Termite's Avatar
Join Date: Apr 2008
Posts: 6,520
Rewards Points: 2,000

Whoa, there's a lot to talk about here...

Your stacks will usually be 3" in a residence, as will your underslab "mains". But everything is sized based on the DFU's (drainage fixture units) of each individual run of pipe. A 4" drain is not uncommon, but once again it is based on DFU's...Code driven.

3" pipe has to have 1/8" slope (min) per the IPC. 2" and under requires 1/4". Too much slope and your liquids will leave your solids behind.

At a basement bath group for instance, you'll only hit the main drain once from all the fixtures in that group...Not separately.

Don't forget the backflow requirements. BIGTIME important, and it is easy to do wrong. This usually will apply to basement bath groups but occasionally upper floor(s) as well depending on the lay of the land. There's a lot to know about backflow device placement.

I also presume you understand venting and know the requirements???

My suggestion would be to ask for assistance from the local building department. If they're nice, perhaps you could sit down with them and show them a riser diagram of the proposed DWV configuration to make sure that it will work. It would be a shame to have to do it twice and it would be a bigger shame for it not to work.
Termite is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Furnace leak while running AC unit lbartowski HVAC 3 09-18-2009 01:46 PM
toilet drain pipe is crooked on new construction smcmurrey Plumbing 5 12-24-2008 08:32 AM
Proper way to clean the air handler drain lines lithium1330 HVAC 2 11-25-2008 09:48 AM
Wierd Floor Drain "Backup" rawkintrevo Plumbing 9 06-04-2008 07:10 PM
The Bioswale, french drain, deck, drainage dilemma (long) seabright_sc Building & Construction 2 01-05-2008 03:37 PM

Top of Page | View New Posts


Search Engine Friendly URLs by vBSEO 3.6.1