05:02AM | 11/16/04
Member Since: 11/15/04
8 lifetime posts
My son just bought a home that is about 5 years old. Somewhere in the sewer vent system there must be a blower. Every now and then I can hear it cycle and can feel the air movement at a pipe extending from the rear of the home. Also, at every P trape there is a small stand pipe with what appears to be a filter at the end.

Can someone explain this system to me and suggest where this blower might be located?


07:47AM | 11/16/04
The filter looking device by the P traps are probably automatic air vents (AAV). This are used in place of a normal vent that goes out the roof. They are controversial because they require maintenance, removal and may have a health impact from sewer gas. Our traditonal plumbing code, the Uniform Plumbing Code, does not allow them. The new International Plumbing Code does not include many of our traditional protections and they have allowed all AAV's except for one real vent and it can go out the side wall of a house.

I am unaware of a blower in a drain-waste and vent system but would like to hear more. Do you only feel air coming out of the side pipe when you hear the noise? Is there a sewage ejector in the basement? Is the sump pump tied into the drainage system?


08:21AM | 11/16/04
Member Since: 11/15/04
8 lifetime posts
Lonny: Thanks for the reply. What type of maintance do the AAC's require? From what I have subsequently read all they appear to be is a check valve and at most need to be replaced if they begin to stick.

Relative to the blower. What is a sewage ejector? As far as I can tell the sump pump is only for the surface water.

There is what looks like one sewer vent stack coming through the roof, if that means anything


09:34AM | 11/16/04
The maintenance is just to check to see if they are still operating correctly. Replacing them, not repairing, is the cure. A sewage ejector if a basin and pump system that pumps the sewage up to the house drain pipe if there is not underfloor drainage. Sump pumps are only for surface water but sometimes they wrongly get connected to the sanitary drainage system. Does yours go out separate? There should be one regular vent to the exterior. What is the pipe going out the side wall? Could it be your furnace vent?

If you have plastic piping coming off your furnace then it has a blower. This is not connected to the drainage system.


10:50AM | 11/16/04
Member Since: 11/15/04
8 lifetime posts
Lonny: The house does not have a sewer ejector system.

I have double checked the pipe exiting at the rear of the house. It definitely goes to the drain system. The furnance pips are a long way from this ine.


12:40PM | 11/16/04
What is on the other side of this wall? If it's a kitchen sink then it is possible you have an outside cleanout for it. Do you see threads? Is there a 90 on it or a screen? How far up from the ground? What size and kind of pipe? Is it 2" plastic? If you have a rectriangular metal piece it may be a dryer or bathroom vent. Are you on a sewer system or septic?

Try to identify sound location and frequency. What a mystery.
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