Sewer Gas and Sump Pump
Summary: Sewer gas is noxious. The smell is often unmistakable and most people find it highly offensive. There are significant dangers associated with sewer gas as it contains explosive methane gas and sewer gas can deplete oxygen in a room or a house. In other words, don't ignore sewer gas!
Related Articles: Sewer Gas Smell, Foul Odor, Bathroom Sewer Odors, Shower Drain Odor, Clog Free Vent Pipes
DEAR TIM: We have just finished renovating our bathroom and we have a problem with sewer gas smells. The house is a split-level on a septic system. This lower-level bathroom drains into a holding tank or sealed sump. When the tank reaches a certain level, the water and waste is pumped up to where it can flow into the septic system via gravity. Each time the pump operates, the new toilet bubbles and loses some water in the bowl. Within a few minutes, the room is filled with a stinky odor. What is the cause and how do we fix this? My beautiful new bathroom stinks. Kathryn C., Destin, FL
DEAR KATHRYN: I am at a slight disadvantage since I can't actually see the sump installation, but my 20+ years of being a licensed master plumber tells me the sealed sump is not vented properly.
Sealed sumps such as yours must have an isolated three-inch vent pipe that leaves the sump and extends up through the roof of your home. This sump vent must not connect into the regular vent piping that serves the rest of your plumbing system.
This special vent is required for any number of reasons. For starters, each time waste and water enters the sump, some of the air in it must leave the sump as the added water and waste displaces this air. The air exits the sump via the vent pipe.
But when the sump level rises to a point and triggers the sump pump to turn on, the exact opposite happens. The water leaves the sump and air must re-enter the sump to take up the space that was occupied moments before by the sewage. If air doesn't enter the sump through a vent, the water leaving the sump via the pump creates a powerful vacuum.
In fact, this is exactly what is happening per your description of events. The pump turns on and the toilet bubbles. The bubbling is the suction you are hearing as the air-starved sump gasps for air. Just before the bubbling or gurgling starts, it has sucked some water backwards from the toilet bowl back towards the sump. This is why you have a lowered water level in the toilet bowl each time the sump operates.
Once the water has been sucked from the toilet bowl, it creates an open pathway for the noxious sewer gases from the sump and septic system to enter your home.
As soon as the plumber comes back and installs the new vent line, your bathroom will start to smell as fresh as a field full of fragrant wildflowers!
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Comments:
Lawrence Walker 28 Nov 2007, 07:49
I have a bad smell comming from our washtub pump in the basement. Last
year we had two plumbers look at the situation, and they said we needed a
new pump. The pump works fine. It is the smell that we were upset about.
In the spring the smell went away, but it has returned in the last few
weeks. I run water in the tub in the morning for a few minutes letting the
pump flush a few times, and it seems to help. Any ideas? I don't want to
spend $500 for a new pump, as our pump works fine.
ATB 28 Nov 2007, 07:59
Please read my past articles about biofilm on the inside of drain pipes. I
feel that is the issue. Type biofilm into the search box at the top of this
page.
Carl Dukes 28 Nov 2007, 10:22
Tim, I am having a problem with sewer gas on the outside of my home. It
seems to be coming from the vents on the roof and I only notice it either
early in the morn or on a cloudy overcast day. I had problems with my
septic system and had it replaced with-in the past year. I detect no odor
around the new installation. Any advise you could give me on how to
eliminate this problem would be appreciated. Thanks carl
ATB 28 Nov 2007, 12:45
Try relocating your vent stacks to the highest part of your roof where they
will have a nearly constant breeze blowing across them.
Toni 09 Mar 2008, 21:02
Yes , We have moved into a new home six months ago and We have a problem.
The Master bathroom has two sinks and both are used daily but one sink has
a foul smell coming up through the drain always and we have the same
problem in our hallway bathroom on one of the sinks in their also and it
too is used always also. The bathrooms are on the top floor and the only
problems with the odor coming up.
AsktheBuilder 13 Mar 2008, 06:03
Toni,
I explain exactly why this happens in several other columns on this website. Type biofilm into the Search Box above to find those columns.
EN 08 Apr 2008, 11:59
I moved into a townhouse last july. Everything seemed ok. The passed three
weeks however a terrible smell is comming from the sump-pump and kitchen
drains. The landlord called a drain man out and he cleaned out the main
drain but it still smells. Pryer to this I had to call a plumer out three
different times to fix the toliet. I don't know what could have changed.
Thanks EN
AsktheBuilder 12 Apr 2008, 09:58
EN,
I suggest you read all of the columns of mine that have the word "biofilm" in them. Also read all of my columns about Sewer Gas. Be sure to read all of the comments and my replies.
Jill 10 Aug 2008, 19:26
After heavy rain, I get a sulfur/sewer smell only in my laundry room. The
"P" trap in laundry sink has water in it so it's not coming from there. The
plumbers checked the vent pipe for blockage (none found). Check the height
of the vent pipe (OK). Poured bleach-like substance down it to see if the
bleach smell came into the room (no smell detected). The plumbers are
stumped and I'm tired of getting this smell everytime we get a heavy
downpour. Please help. Thanks.
Roger 12 Aug 2008, 07:07
Jill,
Do you have a floor drain in the laundry room? If so, have you poured any water in it recently? Some times the water in the drain will evaporate. Try pouring some water down the drain and see what happens after the next rain. View all comments |
