I have a new home (1.5 years old). Immediately upon moving in I started to notice intermittent smell. A sewer smell that starts in the basement utility room and lower bathroom and then spreads through out the house. The smell is almost always strongest first thing in the morning and most pronounced when it rains lightly over night or in the early morning.

First the basics:
* Septic Bed is in front of house. Above grade from the basement.
* Plumbing configuration has an injector tank in the basement services two bathrooms and a small kitchen area.
* House is large and tall. Vent stacks are at least 25-30 above the septic bed
* The utility room has a vent stack (services 2nd storey (2 bathrooms), Main floor (washing machine), basement (bath)
* All fixtures get used at least 1 per week
* Package of Septic system enzymes are being added to the septic tank on a monthly basis

When we first experienced the smell. We called the Plumber. He went to injection tank and sealed it with a silicone caulk and screwed the lid back down. The tank was not sealed.

However we had a re-occurrence. Plumber came back, replaced the wax ring on the basement toilet.

3rd occurrence, tracked to faulty air inlet value on laundry room sink (note: not part of vent stack mentioned above, this had one of those small inlet that pull air from the house when used). That was replaced.

The problem has continued. It was good all winter and now that the summer is here, the smell is at least 1 per week. As I said, the smell start in the lower basement corner. The room with the main sewer line, the injector pump and the vent stack for the lower bathroom. The bathroom has the second strongest smell (it is next to the utility room) then the kitchen (above).

I have a feeling it has to do with the air pressure outside and the fact that we have a heavy clay soil (Georgia). My theory is that when it rains the ground can't allow the "air" to escape from the septic bed and the gases build up over night, forcing the air back into the basement of the house where it escapes through some fault/fracture in the lines.

I think my next step is to have the vent line smoked or peppermint tested for leaks. Of course I'm not 100% it is the vent line. I know the room has the strongest smell. This is a rough diagram of the space

A - Sewer Line
B - Injector Tank
V - Vent stack


****************A**

* * B *

* * *

* Weak * *

* Smell * *

* (TV) * Strong *

* * Smell *

* * *

********** ***********

* *

* Utility Area Strong Smell *

* *

**********************V******

* *

* Medium Smell *

* (Bath) *

**************





Any suggestions? Thanks in advance.

Is there a dedicated vent on the ejector pit or is it tied back into the house vent system? Regards, Tom

It appears so. There are two 2 inch pipes out of the top of the injection tank. Since the waste flows under the floor into the tank, and the second one is connected to the main sewar line. The other must be a vent stack.

If it is 100% dedicated - not completely sure as there is a powder room above the injection tank on the main floor

The reason the pit vent is dedicated is that as well as pulling air in as the pit discharges it also forces air out as the fixtures connected to it flush and drain. If the pit vent were tied into the lavatory vent in the powder room then every time you flushed a basement toilet you would pressuring up the house vent system with sewer gas. Since this is what you're smelling I would check the pit seals again and make sure if the pit vent's run out the roof or if the plumber got lazy and tied it back into the house vent system. Good luck. Tom

Ok. It took a week for me to have the time to look into this. I crawled around the attic and it does appear that the pit stack is a free standing vent. In the attic all the standard pipes (upper bathrooms & various other pipes) come together in a big spider like mess of pipes and attach to one vent stack. There is a separate vent that as far as I can tell is not tapped into at all.

I called the plumber and I'm going to have him smoke the pit vent to see if we can see any leaks and reseal the pit. Then we wait again.

Please let us know what the plumber finds. It will help the next homeowner that has your problem. Good luck, Tom

I have been talking about this here before, so briefly :

When I was growing up ( in big city ) , we used to predict rains by smell of the city sewers. They smelled the strongest day before rain and during the rain. Years later, I have been told that this is caused by low atmospheric pressure that keeps gases close to the ground. (Same phenomena can be observed with chimneys: before rain, smoke from chimney rolls over the roofs. Under normal conditions, smoke raises straight up )

You've got many good answers posted here. Hope you they will be instrumental in solving your sewer smell problem.

Stay tunes. The Plumber is scheduled to Smoke Bomb my house on the 15th... Bomb's away.

Well, Let's talk about an interesting experience. The plumber came on the 15th and did what they needed to do. Bombs away! Immediately smoke filling the attic (remember I'm smelling stuff in the basement). Apparently the HVAC people elected to cut into the vent stack and drain the attic furnace dripline into the stack. They just cut a hole and put a 1.5 inch drip line in the hole and took some caulking to "seal it up".

$600 later we had that hole repaired and we could get on with the test.

Another Bomb is dropped and the attic holds. We look into the basement. As expected the Extractor pit is leaking. The original installation of the pit did not put gaskets around the pvc pipes that are in the top of the lid. The vibrations from the unit worked the caulking lose and the smell/gas escapes.

So, lesson learned - check the lid to the base for a gasket and clauking AND the 2 pipes on the top (vent pipe and extract pipe) for a gasket and caulking. Now we wait to see if the smell is fixed.

A sidenote. The new plumber did not like that the "pit" was deeply sunk into the ground (dirt) and how the concrete floor around the pit from the foundation was done. If you get close to the pit you smell the "earth" smell from the dirt. If this holds our next step is to pour 2-3" concrete around the pit (below the lid) as a barrier - This MAY be the source of the odd bugs we get in the house which is a different problem that is driving us nuts.

I will wait a few weeks and report back if the problem is truly solved, but the whole thing ran me another $1600 bucks.

Did the extra caulking resolved the problem ?

I'm having a similar problem since I've installed a lift pump for a new basement bathroom. I have all the proper vents, but sometimes I smell like a mixture of 'chemical/stale water/mild sewage'.

I've removed the caulking and then the lid of the lift station but I cannot smell anything from the tank (the new bathroom has not been used yet.. so no soilage in the tank).

Yet, the area where the lift pump is located is also where the main drain goes through the cement wall into the outside sewage tank. All this area smells the strongest and I can't pin-point the problem.

There is no gurgling of water on any fixtures in the house. If I sniff the vent stack on the roof and I smell sewage, does this mean that the vent stack is not blocked ?

So far the smell is gone. The key for us was that the pipes (and the lid) were missing the gaskets. In our case when the macerator kicked in the pipes vibrate and the clauking cracks. So Gaskets were key. Now to be fair I typically didn't smell it much odor in the winter; it seems to be a spring/summer issue for me.