You may have a sewer back up in your home if your washing machine is leaking or if you smell a foul odor. If you have a sewer back up, the water that is backing up through your home is making your washer overflow. The overflow drain will not be able to handle the amount of water that is coming into it. The overflow will back up and spill water through your home. This water will then overflow the washing machine where it will then spill into your basement. This can cause the sewer back up to become worse and worse. If you have a sewer back up, you should turn off the water that is coming into your home and call a professional to help you fix the problem. If you have no idea if you have a sewage back up or if you need to get a professional to help fix the problem then you can contact your local municipality.