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 AAV installation on new fixtures
Author: jpplumbsaway (Non-US)

How many AAVs should be installed (and where's best place(s) in the line?) if a tub, sink, and toilet are being installed at the end of, and in that order upstream from, the main waste stack on the second floor? I am planning where to make a vented area(s) in the drywall for it(them).

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 Re: AAV installation on new fixtures
Author: Paul48 (CT)

They shouldn't be installed at all. The new fixtures should be properly vented.

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 Re: AAV installation on new fixtures
Author: jpplumbsaway (Non-US)

Is the main 3" vent stack off of the ground floor toilet/sinks waste line not sufficient for the positive pressure (septic gas issue) and, therefore, I need only worry about preventing the negative pressure and siphoning from the p-traps of the new upstairs drains?



Edited 1 times.

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 Re: AAV installation on new fixtures
Author: SMSPlumbing (PA)

This is hard for us to know how and where to put vents, when we do not have a diagram or pictures.

Good plumbers will not use AAV vents, unless it is the last possible thing that will work.

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 Re: AAV installation; If I have to use them, then...?
Author: jpplumbsaway (Non-US)

Thanks for that...
I take the position that installing AAVs is my only option since I'm working in an old house with thick stone walls and an old, steep, metal roof - I'd like to avoid putting in new vent stack(s) through either of these.
Would installing an AAV on each 1.5" drain line of the sink and bathtub be enough to prevent the toilet, slightly upstream (at the end) of the 3" waste line, from causing a siphoning issue on those neighbouring drains' p-traps or should another separate auto vent be installed for the toilet?



Edited 1 times.

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 Re: AAV installation; If I have to use them, then...?
Author: bernabeu (SC)

build an interior bulkhead/soffit to conceal the new vent stack ... the roof penetration should be left to the 'pros' ... if you can't do the job properly, then, don't do it at all

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Retired U.A. Local 1 & Local 638
~ Measure Twice & Cut Once ~ ~ Eight 4 Eight ~

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 Re: AAV installation; If I have to use them, then...?
Author: Paul48 (CT)

Standing seam roofs are everywhere now.Penetrating them properly is a piece of cake. How much would a roofing company(experienced with standing seams) charge you to put a boot on a pipe?Your only concern would be making sure you're mid-seam.

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 Re: AAV installation on new fixtures
Author: LemonPlumber (FL)

The aav is only to be used to dry vent section protection on each trap and will not function if the main dfu can be fouled at the minimum rated flow.So you should carry full sized or over sized tubing pasted all main fixtures to the vent terminal and then use the aav to protect all traps along the discharge line.Take special care where the washing machine passes any other major fixture as it is a double drainage issue in use.And although not called for, may require down stream tubing size increase.Please atmospheric vent each bath group if possible.if not over size the drain main to allow bubble/foam failures to be reduced.

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 Re: AAV installation on new fixtures
Author: hj (AZ)

You would either need one at EVERY fixture, or at points which are common to two or more fixtures. We CANNOT tell you which because we do not know the specifics of your plumbing, and we take a very dim view of using AAVs in the first place.

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 Re: AAV installation on new fixtures
Author: hj (AZ)

The 3" waste may have NOTHING to do with venting the fixtures you are asking about.

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 Re: AAV installation on new fixtures
Author: LemonPlumber (FL)

Sorry HJ.where three inch is the main size and any toilet down stream of any washing machine with only aav,trap protection will fail.I do not agree.

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 Re: AAV installation on new fixtures
Author: SwimRunPlumb (MI)

If the lav is the most upstream fixture, you can simply stub the drain up through the bottom of the cabinet and put the AAV in the cabinet. That is if you are allowed to wet vent as we are here in Michigan.

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 Re: AAV installation on new fixtures
Author: packy (MA)

why don't you make a single line drawing of your proposed plumbing work and show it to your local inspector when you take the permit?

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 Re: AAV installation on new fixtures
Author: hj (AZ)

How can you disagree? You do not even know what I said.

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 Re: AAV installation on new fixtures
Author: hj (AZ)

According to the instructions at most AAV sites, the "uppermost" fixture is the one which should have the vent through the roof.

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 Re: AAV installation on new fixtures
Author: SwimRunPlumb (MI)

So basically what your saying is that you cannot use an AAV on a wet vented system? The lav is always the furthest upstream on a wet vented system.

If this is the case, there must be tens of thousands of AAV's used incorrectly.

I am not a proud supporter of these things, but yes, I do use them every now and then on basement jobs and island kitchens.

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 Re: AAV installation on new fixtures
Author: waukeshaplumbing (WI)

they typically go under a sink (95% of the time)

ive never put a access panel for one.

you may want to hire a plumber

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 Re: AAV installation on new fixtures
Author: bernabeu (SC)

re: island sink

if you can run the drain - you CAN run a compliant vent



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Retired U.A. Local 1 & Local 638
~ Measure Twice & Cut Once ~ ~ Eight 4 Eight ~

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 Re: AAV installation on new fixtures
Author: hj (AZ)

The AAV has NOTHING to do with a "wet vented system". The recommendation is because ANY system using AAV's MUST have at least ONE vent through the roof, and it is only functional when its connection to the main line is not underwater. THEREFORE, they recommend that it be at the furthest fixture, since that one would be the last to be submerged during a stoppage or other backflow condition.

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 Re: AAV installation on new fixtures
Author: SwimRunPlumb (MI)

Bernabeu- Yes, we all know how to do that, but nobody does anymore (at least in areas that allow AAV's). Yes, I could still do this but how would I ever be competitive with the other guys, especially since many of them will run the one required vent and AAV EVERYTHING else.

hj, on a wet vented system, the lav is always the furthest upstream fixture. Therefore, if you are saying that this must be a real vent, then you are saying you cannot use an AAV on a wet vented system by process of deduction.

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 Re: AAV installation on new fixtures
Author: LemonPlumber (FL)

you said, 3" waste may have NOTHING to do with venting the fixture.And that is what?My time to point out three inch as a regular dwv may leave air flow through out the system as acceptable .This Is often a failed design when all aav's are used!On a three inch system with a washing machine.This is not possible failure .It is designed failure.Where the only vent is not at the end of the 3"run it is guaranteed failure.This leaves the stack system aav use still good to go not any wet vent alternate uses.I state this as my knowledge.Where the wm discharges past any aav .the system is failed@three inch..

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 Re: AAV installation on new fixtures
Author: SwimRunPlumb (MI)

I'm not quite sure what you are getting at Lemon, all I am saying is there are thousands of bathroom groups that pick off the toilet, tub, and then lav with an AAV. At least in Michigan that is.

I am not saying this is a good thing, but since they are approved, they are abused.

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 Re: AAV installation on new fixtures
Author: hj (AZ)

quote; then you are saying you cannot use an AAV on a wet vented system by process of deduction.

You mean you will only have ONE wet vented system in EVERY house? I said the recommendation is that the furthest connection, (and that does NOT necessarily have to be the "wet vent" since it could be a tub or shower vent), be the vent through the roof, NOT that EVERY "wet vent" has to go out the roof. You are trying to be argumentative, or rationalize something other than what I stated.

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 Re: AAV installation on new fixtures
Author: LemonPlumber (FL)

guess being smarter than the upper most fixture?

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