Overloaded Vertical Drain

RalphPeters · 12-20-2012, 10:20 AM

Currently I have two sinks from two adjoining bathrooms connecting to a 1 1/2" vertical drain. I would like to replace the vanity in one of the bathrooms with one having a double sink. This would mean three fixtures would be connected. The double sink would be plumbed so each one would have its own p-trap and connect to a double fixture cross.
I called a local plumbing company and they said they would plumb the new fixtures but that it wouldn't be to code. They said it would be fine having three fixtures just not to code??
What would be the consequences of having three fixtures tied together. Is it just to protect the possible situation where are three fixtures are being used or draining at the same time?

joecaption · 12-20-2012, 10:24 AM

My guess is without the 2" line that should be there it my suck the water out of the trap as it was draining.

tylernt · 12-20-2012, 10:51 AM

Lav sink is 1 DFU (Drain Fixture Unit):

http://www.engineeringtoolbox.com/dr...es-d_1077.html

Looks like 1 1/2" pipe can support up to 3 DFU:

http://www.engineeringtoolbox.com/fi...es-d_1104.html

So on the face of it, 3 bathroom sinks on a 1 1/2" drain might indeed be legal. However there may be other restrictions that apply that are in the text of the code, but not mentioned in the above table... so it's not a slam-dunk. Plus you're in Canada, dunno what is code up there.

**TheEplumber** · 12-20-2012, 12:30 PM

Local codes play a part in how many DFU's a pipe will handle. Vertical pipes generally allow more then horizontal too.
I would not put 3 lavs on a 1.5" pipe.
And I would not use a sanitary cross- another code violation- at least for me

Alan · 12-20-2012, 09:11 PM

To further add to the code ruling on this issue (UPC Based response) :

704.2 Two fixtures set back to back or side by side within gthe distance allowed between a trap and it's vent may be served by a single vertical drainage pipe provided that each fixture wastes separately into an approved double fixture fitting having inlet openings at the same level.

706.2 ..... No fitting having more than one inlet at the same level shall be used unless such fitting is constructed so that the discharge from one inlet cannot readily enter any other inlet. Double sanitary tees may be used when the barrel of the fitting is at least two pipe sizes larger than the largest inlet.........

Also agree with above comments about 1-1/2" drain being too much for 3 lavatories.

RalphPeters · 12-21-2012, 12:43 AM

I appreciate the replies.
What would be the consequences of an overloaded drain?

Javiles · 12-21-2012, 08:01 AM

slow draining when multiple sinks in use. ger gulling, possible trap siphon. look don't knock yourself out use the correct combination on the drains you'll be alright. unless its inspected work.

RalphPeters · 12-21-2012, 10:26 AM

Quote:

Originally Posted by Javiles

slow draining when multiple sinks in use. ger gulling, possible trap siphon. look don't knock yourself out use the correct combination on the drains you'll be alright. unless its inspected work.

So would I want the double fixture fitting above the t fitting? I can only find the double in a 2 x 1 1/2 x 1 1/2 x 1 1/2 so a reducing bushing would be necessary?

Javiles · 12-21-2012, 01:55 PM

1 1/2 double sanitary tee. they make m... on the top use a 1 1/2 (street) sanitary tee. slips into the hub. 2 inch will take up to much space between the arms. be careful that fitting in the picture is a combo not a sanitary

ben's plumbing · 12-21-2012, 06:45 PM

1 1/2 would be to small...consequences would be its done wrong so it will drain slow ....Iam sure you don't want that because you came to this site for the answer....you now have it....good luck ben sr

Javiles · 12-21-2012, 11:38 PM

Quote:

Originally Posted by ben's plumbing

1 1/2 would be to small...consequences would be its done wrong so it will drain slow ....Iam sure you don't want that because you came to this site for the answer....you now have it....good luck ben sr

Agreed but that's what he has in the wall on the vertical 1 1/2

12-20-2012, 10:20 AM	#1
RalphPeters Member Join Date: Feb 2010 Location: BC,Canada Posts: 61	Overloaded Vertical Drain Currently I have two sinks from two adjoining bathrooms connecting to a 1 1/2" vertical drain. I would like to replace the vanity in one of the bathrooms with one having a double sink. This would mean three fixtures would be connected. The double sink would be plumbed so each one would have its own p-trap and connect to a double fixture cross. I called a local plumbing company and they said they would plumb the new fixtures but that it wouldn't be to code. They said it would be fine having three fixtures just not to code?? What would be the consequences of having three fixtures tied together. Is it just to protect the possible situation where are three fixtures are being used or draining at the same time?

12-20-2012, 10:24 AM	#2
joecaption Member Join Date: Nov 2011 Location: Hartfield VA Posts: 18,840	Overloaded Vertical Drain My guess is without the 2" line that should be there it my suck the water out of the trap as it was draining.

12-20-2012, 10:51 AM	#3
tylernt Special User Join Date: Jul 2012 Location: Idaho, US Posts: 551	Overloaded Vertical Drain Lav sink is 1 DFU (Drain Fixture Unit): http://www.engineeringtoolbox.com/dr...es-d_1077.html Looks like 1 1/2" pipe can support up to 3 DFU: http://www.engineeringtoolbox.com/fi...es-d_1104.html So on the face of it, 3 bathroom sinks on a 1 1/2" drain might indeed be legal. However there may be other restrictions that apply that are in the text of the code, but not mentioned in the above table... so it's not a slam-dunk. Plus you're in Canada, dunno what is code up there. __________________ The above post is for entertainment purposes only. Its contents may, and probably will, lead to legal liability and damage or loss of property, life, or limb. Use at your own risk.

12-20-2012, 12:30 PM	#4
TheEplumber call me E Join Date: Jul 2010 Location: Idaho Posts: 4,150	Overloaded Vertical Drain Local codes play a part in how many DFU's a pipe will handle. Vertical pipes generally allow more then horizontal too. I would not put 3 lavs on a 1.5" pipe. And I would not use a sanitary cross- another code violation- at least for me __________________ When posting in forums, letting us know your location will help others give better feedback/advice/solutions to your questions

12-20-2012, 09:11 PM	#5
Alan Doing it myself Join Date: Apr 2006 Location: Crescent City, CA Posts: 3,454	Overloaded Vertical Drain To further add to the code ruling on this issue (UPC Based response) : 704.2 Two fixtures set back to back or side by side within gthe distance allowed between a trap and it's vent may be served by a single vertical drainage pipe provided that each fixture wastes separately into an approved double fixture fitting having inlet openings at the same level. 706.2 ..... No fitting having more than one inlet at the same level shall be used unless such fitting is constructed so that the discharge from one inlet cannot readily enter any other inlet. Double sanitary tees may be used when the barrel of the fitting is at least two pipe sizes larger than the largest inlet......... Also agree with above comments about 1-1/2" drain being too much for 3 lavatories. __________________ Journeyman Plumber

Overloaded Vertical Drain