Smelly vent stack.

[CSLufkin]

Anyone know of a product or any good way to eliminate the septic tank smell from drifting around a customers back yard from the vent stack that comes thru the roof? The pipe has been extended up even with the ridge line and the natural downdraft still pushes it down into the Deck / back yard area.

 

[bimr]

Don't know of any product, but you can always run the vent stack horizontally through the attic and have it penetrate the roof somewhere else.

 

[CarlB]

How about a cap?

OK maybe not. Is this a vent directly from a tank? Around these parts there's no vent for the tank, other than it can vent into the building plumbing & vents, and for a properly operating tank there is negligible odors. Is there maybe something else causing the odor?

 

[CSLufkin]

This is a vent off the "Top" of the system in the house, not a vent directly from the tank. These vents are common around here and I know of several cases where you can smell them, in fact they have earned the name "Stinkpipes".

You may be on to something with the odor being the problem, rather than the vent malfunctioning. Anyone else have any ideas.

 

[CarlB]

Found a few sites that have products to address this, here's one:

http://www.sweetfilter.com/

 

[SlideRuleEra]

Install an Air Admittance Valve (AAV) - they permit only the one-way flow of air (into the system) to allow proper drainage. Here is a typical link

http://www.toolbase.org/TechInventory/techDetails.aspx?ContentDetailID=851

Most building codes, but not all, allow their use - you may want to check.

http://www.SlideRuleEra.net

 

[dik]

You might want to check with a local septic system installer. The odour could be indicative of anerobic activity and this should be corrected first. Most properly working septic systems are relatively odourless.

Dik

 

[bimr]

There seems to in error of some sort in the design of the system.

In the first case, the entrance to the septic tank should be submerged. The service pipe generally enters the septic tank and turns down under the water. Therefore, it is not possible for odors to travel from the septic into the house.

Secondly, you should not have much air flow going up the stack, so you should not be having the odors travel very far.

The stack is supposed to be about 12" above the roof penetration and 3-4" in dia.

Is there only one stack? The practice around here is to collect all vents into one roof penetration.

Is it possible that you have an empty floor drain trap that is allowing air to go up the stack?

Air admittance valves are not used on top of stacks nor are the sweetfilters.

 

[CSLufkin]

Thanks for the responses guys.

bimr,
The norm around here (at least on residential systems) is for the septic tank inlet to stick into the tank a couple inches and stop. I have never seen one that turns and goes down, I think this would make floating solids plug the line.

I agree that there should not be a lot of air flow up the vent line, I have no idea why it so heavy at times.

The stack is 3" schedule 40 and it is probably more like 24" above the penetration. All vent lines ar tied together in the atic and run thru this one roof penetration.

No floor drains are tied in, I checked all sink traps to ensure they were full.

Any more thoughts as you mull this stuff over?

 

[bimr]

Perhaps the inlet to the septic tank is the problem. If you look at the following examples, they all have an inlet baffle.

Without the baffle, you may be getting some type of stack effect where the heat in the house is causing air to rise through the plumbing stack.

"A septic tank must have devices such as baffles or sanitary tees to help ensure that settling occurs, solids are retained and venting is provided (Figure 1). An inlet device prevents the scum layer from building up and plugging the end of the sewer pipe."

http://www.ces.purdue.edu/extmedia/HENV/HENV-5-W.pdf.

http://www.ianrpubs.unl.edu/epublic/pages/publicationD.jsp?publicationId=253

http://www.inspect-ny.com/septic/tanktees.htm

http://www.thenaturalhome.com/septic.html

Here is another report on odors:
How to Diagnose, Prevent, or Cure Odors and Hazards from Gases in Septic Systems

 

[rodhouser]

Plumbing vents routed through the roof are an unlikely source of the odors. If they were, all residential suburbs (sewered or unsewered) would stink like heck.

A more likely source of the odors are failing septic tanks and leach fields in the area. This is particularly common in communities that rely soley on septic tanks for domestic sewage treatment and disposal.

There are a lot of communities out there who don't want to pay for centralized sewage collection and treatment systems either because they're too cheap and don't want their taxes to increase, or they're trying to prevent growth. The end result is stinky neighborhoods and horrible stormwater pollution.

If the odor is limited to the interior of the house, it's good to check for seldom-used p-traps that may have dried out. Dumping a bucket of water down the drain of a rarely used shower will reprime the p-trap and prevent odors from backing up into the house.

 

[cactusboy1]

Make sure the tank is gas tight. This might be as simple as sealing or repacing your lids. Also, Orenco Systems makes a carbon filter that slips on the end of PVC pipe for the vent pipe on your roof. If worse comes to worse you can add a small fan to actively vent the system.

http://orenco.com/catalog/PF26PT109.asp?pf=26