# septic tank vent



## themavinator (Apr 15, 2009)

When does a septic tank need a vent? I'm working on a 1500 person assembly hall with two separate bathroom buildings and a few other bathrooms. The plans show a vent for the tank itself. Why is this necessary? I thought you weren't supposed to introduce oxygen into a anaerobic system.


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## Shoot'N'Plumber (Apr 27, 2013)

Only times I've been told a septic tank needs a vent is when the inspector mistook it for an interceptor at which I would politely ask "are you sure!" Then the light would turn on.


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## BOBBYTUCSON (Feb 8, 2013)

ive never vented a septic in m life


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## Master Mark (Aug 14, 2009)

it is on the plans because the dumb-ass architect does not know any better and drew it in just because


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## PLUMBER_BILL (Oct 23, 2009)

themavinator said:


> When does a septic tank need a vent? I'm working on a 1500 person assembly hall with two separate bathroom buildings and a few other bathrooms. The plans show a vent for the tank itself. Why is this necessary? I thought you weren't supposed to introduce oxygen into a anaerobic system.


*North of Allentown, in a non-sewered area. The call came in for a sewer gas smell, investigating I found on the 2nd floor a full bath and a roughed in only bath area. Opening the floor in this room, I found the tops of all copper eaten away. Reason sewer gas from the septic tank flowing into the house --- and through the vents on the roof, and no water to wash the interior of the pipe. We replaced the eaten through sections [copper DWV]. We also cut in the house drain a san tee with a riser to 12" above ground with a mushroom vent cap. Looked like a vent, but was actually a fresh air inlet. The vents could now drawn fresh air to offset the sewer gas. Same --, as we do use house traps in our locality and there you would have to install fresh air behind the trap. *


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## themavinator (Apr 15, 2009)

I'm in Peru right now and I think the reason they put it in there is because they don't vent all of the fixtures so they don't want pressure building up in the tank but I'm not sure.


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## plbgbiz (Aug 27, 2010)

Reread Master Bill's post. Vents are not just for drainage.


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## Master Mark (Aug 14, 2009)

plbgbiz said:


> Reread Master Bill's post. Vents are not just for drainage.



Master bill is right, but that kind of trouble was waaaaay back in the day when copper pipe was used and it is not necessary with sch40pvc.....

the main trap going out of the house is something that is acutally a great idea that has gone out of style long ago..... If I were building a new home I would probably consider installing a 4 inch trap with clean outs on both sides of it....


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## themavinator (Apr 15, 2009)

Basically I want to eliminate the vent altogether because if it's not necessary then it's a lot of extra work because the way the have it drawn is a flat vent running all the way to the edge of the property because they are concerned about smell.


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## nhmaster3015 (Aug 5, 2008)

You guys don't have septic installers licenses? Lol. Ok, here goes. In the old days when the leach field was perforated pipe we didn't need to vent either the tank or the field but with modern chambered systems, the flushing of high volume fixtures can cause fluid to move into the tank faster than the air can be pushed out. Same with the leach field so these days the septic design generally calls for a vent on both and yes, it looks like hell generally. Plant a bush.


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## plumbdrum (Nov 30, 2013)

nhmaster3015 said:


> You guys don't have septic installers licenses? Lol. Ok, here goes. In the old days when the leach field was perforated pipe we didn't need to vent either the tank or the field but with modern chambered systems, the flushing of high volume fixtures can cause fluid to move into the tank faster than the air can be pushed out. Same with the leach field so these days the septic design generally calls for a vent on both and yes, it looks like hell generally. Plant a bush.


 Or a wishing well


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## PLUMBER_BILL (Oct 23, 2009)

<SNIP>

the main trap going out of the house is something that is acutally a great idea that has gone out of style long ago..... If I were building a new home I would probably consider installing a 4 inch trap with clean outs on both sides of it....[/QUOTE]

*Good idea, but c/outs on both sides won't work. The house side must be a riser with a mushroom cap. Reason the trap 4" will stop a toilet from flushing because the air between the flushing toilet and the 4" trap will stop the flushing water. So in reality the fresh air inlet works two ways.
Relief of air and inlet of air to ventilate the piping. *


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## themavinator (Apr 15, 2009)

nhmaster3015 said:


> You guys don't have septic installers licenses? Lol. Ok, here goes. In the old days when the leach field was perforated pipe we didn't need to vent either the tank or the field but with modern chambered systems, the flushing of high volume fixtures can cause fluid to move into the tank faster than the air can be pushed out. Same with the leach field so these days the septic design generally calls for a vent on both and yes, it looks like hell generally. Plant a bush.


Ok cool. So my next question would be: what is a chambered leach field?


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## wyrickmech (Mar 16, 2013)

No vent required a septic system has very little air in the tank and a ( chamber system) needs no vent. The chamber system is simply a chamber that requires no rock for space to allow volume of fluid time to percolate into the ground. The only vent required on a septic system is the house venting system to keep the water column within the required 1 in to maintain the water seal of traps.


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## chonkie (Jul 31, 2014)

Never had to vent a septic either, but we only do aerobic. Are you sure it is going to be anaerobic and not an aerobic system? Just seems odd to go with anaerobic.

It's not the architect that plans the septic system, at least not here, and probably most places. Registered Sanitarians, or whatever everyone else calls them. If it is the same with OP's location, then most likely the vent stays as designed. Maybe it is anaerobic and they are trying to help control the rotten egg odor from the anaerobic bacteria byproducts.


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## chonkie (Jul 31, 2014)

themavinator said:


> Ok cool. So my next question would be: what is a chambered leach field?


Chambered system, not leach field.


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