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03-16-2010, 07:02 PM   #1
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## how to calculate critical distance

the building is 3 stories.for the moment there is nothing plumbing wise on the 1st floor and i am doing 1st floor plumbing.

i will run a vent for the arm where all 1st floor drains are on before they all tie in to the main stack/main vent. this vent will either connect to the main vent on upper levels or go directly above the roof. this vent is 6-7ft away from the main vent/main stack.

1. My question is: to calculate the Critical Distance for each drain i am putting on 1st floor, do i use the main vent or the added 1st vent?

2. Also, if any drain is within the CD, i don't need to add any aux venting, right? the handyman who is helping me with the plumbing says that plumbers like to have the aux venting for each drain just to make sure.

03-16-2010, 10:41 PM   #2
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First you need to do a plumbing layout for all three floors to calculate (DFU's Drain Fixture Units) This will help you to calculate vent size and building drain size.

I think you are calling critical distance the maxium distance a traped fixture can run horizonal that is attached to a vertical stack. Not sure

So

1 1/4" is 5'
1 1/2" is 6;
2" is 8'

If you are plumbing a building that has three floors my suggestion is to hire a Pro to give advise and layout. There are many rules to code and some plumbers will hire out as an advisor so that you get it right.

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 03-16-2010, 11:01 PM #3 Member     Join Date: Jul 2009 Location: Canada Posts: 297 Rewards Points: 306 when talking about the maximum distance, "1 1/4" is 5' 1 1/2" is 6; 2" is 8' " is it the distance between the drain trap and 1. the main stack , or, 2. the venting for 1st floor? also, when it is within the max. distance, there is no need to add any aux venting, right? for the DFU, i have 2 vanity, 2 WC, one washer, one tub, one sink, using 3" drain and 2" vent. Thanks a lot
 03-17-2010, 08:39 PM #4 Member     Join Date: Jul 2009 Location: Canada Posts: 297 Rewards Points: 306 anyone please?
 03-19-2010, 08:34 AM #5 Member     Join Date: Jul 2009 Location: Canada Posts: 297 Rewards Points: 306 can anyone give any input please? thanks a lot.

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