Leaking sewer pipes can be found using the same methods above, except your sewer lines aren’t connected to your water meter, so that won’t help you. There are a few critical differences between a leaking sewer pipe and a leaking water pipe.
If you can smell sewage in your walls or home, that’s a sign a sewer pipe is leaking, exposing your home to disgusting fumes. If you find the wall where the smell is almost unbearable, that might be where the line is leaking.
Mold growth from humidity:
Just like a leaking water pipe, mold growth is a clear sign of moisture behind your walls. In this case, with a leaking sewer pipe, the increased humidity from the leak causes mold to grow just at the right temperatures.
Rodents and insects love to crawl and creep inside your sewer pipes when there is an opening. If you see signs of rats or other pests, think before you call the exterminator. The problem might be a nest somewhere, but it could be they are coming from your sewer lines. If that’s the case, call sewer line professionals.
A vapor test can be performed where a non-toxic vapor is pumped through your sewer system from the vent openings on your roof. If there is a crack in the sewer pipes behind the wall, the vapor will fill the empty space behind the drywall and will make its way out of electrical outlets or other openings. Since a sewer system should be air-tight, any visible vapor inside your home would indicate a crack.
Read also – Signs of a cracked sewer pipe