In some cases, the main sewer line can clog if you dump things that don’t flush well down the pipes. This applies particularly to oils (usually from cooking) and paper items that don’t completely dissolve in water. Sanitary products such as wet wipes, feminine hygiene products, and even thicker toilet paper can cause an obstruction in your main sewer line and back up water and waste through your toilet. While the main sewer line pipe is usually 6 inches in diameter and doesn’t clog easily, a lot of loose material can still pose a risk over a long time.
More often, it’s the neighbouring trees that cause a clogged sewer line. Tree roots are naturally attracted to the hot and moist sewer lines passing through the soil. Small roots can creep in through cracks or looser joints in the pipes. Because sewers can be full of nutrients required for abundant plant growth, the roots will quickly spread throughout the sewer line. Eventually, the roots will overgrow the entire sewer line diameter and clog it by itself. But before that can happen, debris such as toilet paper or other hygiene products will snag on the outlying roots and pack up in the sewer line until nothing more can go down.
The most obvious sign of a main sewer line clog is slowly running drains. If it takes an unusually long time to drain the water in your shower or sink completely, and you notice it happening with all the drains in your home, the main culprit is the main sewer line to which all pipes connect.
Another more disruptive sign of a clogged main sewer line is backed-up showers and toilets. If you flush your toilet and there’s nowhere for the water and debris to go, the water will run up the lowest drain in your house, usually the basement or the bathroom drain. Water backing up the drain can also happen at the washing machine, showers, baths, or sinks. Cleaning the backed up water can be a messy and smelly job, and you won’t have a place to dispose of the wastewater since it will just repeat the problem if you flush it down.
Do note that if only one of your drains is backing up consistently, the problem usually lies before the main sewer line. In that case, only the drain pipe in that room will need unclogging. Main sewer line servicing is only required if all the drains in your house are malfunctioning.