Hi everyone,
I recently moved into my new home ( built one year ago). Once in a while, there is a really bad sewage smell when I use the washing machine. The washing machine is in the basement. I had to install a pump with a tank in the basement since the house is deeper then the septic tank. The water from the toilet, the shower or the washing machine is directed into that tank and once in a while the pumps starts and pumps the used water into the septic tank (that works fine)
My question is, why is there a really bad sewage smell after I use the washing machine?

Your ejector system has two vents.
One that services the fixtures that discharge into the pit. This vent can be tied back into a existing dry house vent. However, the pit vent not only vents air in as it empties the pit but it also expels air out as fixtures discharge into it. You washer discharges with great force and volume causing a lot of air being discharged into the pit vent. This vent MUST be dedicated and not connected back to the house venting system.
Sometimes a lazy plumber will tie the pit vent back to the house vents. Normally this wouldn't harm anything but if the pit vent is connected back to the house system the washer discharge will pressurize the vent system with sewer gas.
Have the vent system checked to see if the pit vent is run in the proper fashion. Good luck, Tom

Wow,
You seem to know what your talking about. Thank-you for the answer and I will probably call my plumber to fix that problem. I don't think its something that I'm able to do myself even tough I'm kind of handy around the house.
Thanks again