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 How Many Plumbing Vents Are Needed?
Author: Niles (CT)

I am considering buying the house next door to mine for rehab. A description of the existing plumbing:
Public Sewer connected
4" vent Stack
Upstairs: Functional full bath, with tub, toilet & sink.
Downstairs: 1/2 bath. Functional toilet, NO sink (ugh!), failed attempt at building a shower-they got as far as the cement board, there is a drain in the floor. I think they ended up using this as a laundry location, because there is a 240v dryer extention cord poking through a hole in the wall! I want to:
1. Install a tub/shower or shower stall.
2. Install a sink.
Now assuming that the existing drain actually drains, I know I can reconfigure it to drain the new tub, and build in a drain for the new sink. Will I have enough ventilation? Do you have to vent every new fixture?

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 Re: How Many Plumbing Vents Are Needed?
Author: packy (MA)

this is a typical massachusetts approved bathroom that is wet vented. does this picture make any sense to you?
[smg.photobucket.com]

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 Re: How Many Plumbing Vents Are Needed?
Author: Niles (CT)

Yes. It appears that all 3 fixtures are vented by one 2" vent pipe.

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 Re: How Many Plumbing Vents Are Needed?
Author: ironranger (MN)

Not allowed in Minnesota, would require a 3" vent, always.

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 Re: How Many Plumbing Vents Are Needed?
Author: packy (MA)

in mass, a house must have one full size vent stack, after that, any additional bathrooms may be vented with a single 2" pipe.
we are not required to run a 3" vent stack for each bathroom.

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 Re: How Many Plumbing Vents Are Needed?
Author: e-plumber (NY)

I doubt any code would require a 3" vent for each bathroom...he must be talking
about the roof penetration pipe size or the full size stack rule in which case it would be 4" (here).

e-plumber
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"The society which scorns excellence in Plumbing as a humble activity and tolerates shoddiness in philosophy because it is an
exalted activity will have neither good Plumbing nor good philosophy: neither its pipes nor its theories will hold water." -
John William Gardner 10/8/1912 - 2/16/2002

Repair your leaking Plumbing fixtures ASAP [www.theplumber.com]
This slow drip will waste 7+ gallons of water per day.

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 Re: How Many Plumbing Vents Are Needed?
Author: PBwrencher (WI)

A perfect system is enough vent/s to try and equalize the air pressure in the plumbing system.:)

The systems are designed to never have more then .5 psi negative or .5 psi plus to promote some air circulation when fixtures are used with a minimum of air flow thus preventing trap seal lose.:think2:

12-21-08, 8:35am Turning Point Day

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A bath a day will keep you healthy in every way.

Safe plumbing brings life and health giving water into our homes, businesses, hospitals and takes away death and disease causing waste.

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 Re: How Many Plumbing Vents Are Needed?
Author: redwood (CT)

Perhaps to understand what venting is for might make you understand what is required. The purpose of vents is to protect the trap seal from siphoning and to equalize the pressures within the DWV system of the building. Sizing depends on the number of fixtures and the flow of water coming out of them. This is measured in DFU's (Drainage Fixture Units) which determines the size of the drain line and the size and # of vents. Sometimes all the vents may tie together before leaving the building and sometimes due to ether high DFU's or just the location multiple vents through the roof would be used. Take a look at the picture below and see how a typical vent system is done. Note how each trap has a vent protecting it. Here is your code information including the link for the 2005 Connecticut Suppliment. [www.ct.gov] Check with your local building inspection department for any additional local requirements.



BTW this drawing is as old as the hills but then again your house might be too! :laugh:



Edited 2 times.

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 Re: How Many Plumbing Vents Are Needed?
Author: PBwrencher (WI)

Installing proper plumbing vents to prevent trap seal lose is not the only reason to correctly vent the plumbing system, it's a primary reason but not the only.:think:

12-22-08, 7:05am

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A bath a day will keep you healthy in every way.

Safe plumbing brings life and health giving water into our homes, businesses, hospitals and takes away death and disease causing waste.

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 Re: How Many Plumbing Vents Are Needed?
Author: dlh (TX)

according to all the plumbers and inspectors i have known protecting the trap seal is the vents only purpose. i think i have read that in a book somewhere also but not sure

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PLUMBERS "Protecting The Health Of The Nation"

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 Re: How Many Plumbing Vents Are Needed?
Author: hj (AZ)

And what would the distant second reason be?

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 Re: How Many Plumbing Vents Are Needed?
Author: PBwrencher (WI)

A good read for you plumbers is "Alfred E Steele" books:)

"High Rise Plumbing Design" and "Engineered Plumbing Design"

His knowledge and ability to explain the multi facets of plumbing design is well worth knowing for all licensed plumbers, instructors and inspectors. Checkout the "ASSE" site!:cool:

12-23-08, 8:25am

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A bath a day will keep you healthy in every way.

Safe plumbing brings life and health giving water into our homes, businesses, hospitals and takes away death and disease causing waste.



Edited 1 times.

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 Re: How Many Plumbing Vents Are Needed?
Author: redwood (CT)

But then again we are talking about a house not a high rise...

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 Re: How Many Plumbing Vents Are Needed?
Author: dlh (TX)

what difference does that make when talking about the reasons for a vent?

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PLUMBERS "Protecting The Health Of The Nation"

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 Re: How Many Plumbing Vents Are Needed?
Author: redwood (CT)

"The purpose of vents is to protect the trap seal from siphoning and to equalize the pressures within the DWV system of the building." I think I said that....

High rise gets a little extreme...

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 Re: How Many Plumbing Vents Are Needed?
Author: dlh (TX)

ok, ill go with that but what need would we have for equal pressure if we werent worried about the traps?

in other words if no trap seal no worries about pressures. so house or highrise it is the same

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PLUMBERS "Protecting The Health Of The Nation"

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 Re: How Many Plumbing Vents Are Needed?
Author: hj (AZ)

In high rise plumbing, you do not necessarily have to know how it works, because the mechanical engineer is going to tell you EXACTLY HOW to install it, and if you do not do it that way because you think you know better, and something happens YOU will be on the hook for the revisions and repairs. Otherwise he is.

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 Re: How Many Plumbing Vents Are Needed?
Author: hj (AZ)

I guess someone could argue that if the pressures were equalized the sewer gases would stay where they are and not enter the building, but that would take a lot of faith.

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 Re: How Many Plumbing Vents Are Needed?
Author: dlh (TX)

yeah. the only time they are going to be even close to equal is when nothing is runnin and then somehow somewhere airflow is going to get into the piping and even with vents will have unequal pressure

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PLUMBERS "Protecting The Health Of The Nation"

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 Re: How Many Plumbing Vents Are Needed?
Author: PBwrencher (WI)

I was not talking Solly about high-rise plumbing systems.:think2:

In the books he explains the multi-purposes of the plumbing vent in all plumbing systems and not just one type. Guys and Gals, Im only trying to help point in a very good direction to help further ones knowledge development if they so strive for a greater interest in the plumbing profession then just the average plumber has.:)

12-24-08, 8:58am Merry Christmas to All:)

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A bath a day will keep you healthy in every way.

Safe plumbing brings life and health giving water into our homes, businesses, hospitals and takes away death and disease causing waste.

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 Re: How Many Plumbing Vents Are Needed?
Author: dlh (TX)

if the vent has any purpose other than protecting the trap seal, as hj stated earlier, it will be in an engineered system and it will be installed to the engineers specificationsor you will not have a job for long and will have nothing to do with anything talked about on a site like this.

go to enginer school and youll learn everything he tells you in that book

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PLUMBERS "Protecting The Health Of The Nation"

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 Re: How Many Plumbing Vents Are Needed?
Author: LemonPlumber (FL)

Hydraulic gradient,Is second term .Unseen and under evaluated.It is the difference between flow and max flow.Good Luck.

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