Signs of a Sewer Mainline Pipe Clog

If you suspect that you have a sewer mainline pipe clog it can be a major problem. It can also be a health problem and plumbing emergency. If the sewer water cannot go out it will start to back up into the plumbing system of the house. If it is determined that there is a sewer mainline pipe drain clog it is advisable that no plumbing in the house be used until you get rid of the clog. One obvious sign is when you one or more plumbing fixture backing up at the same time. The one plumbing fixture that is particularly affected is the toilets. When using different plumbing fixtures you may see some unusual reactions.


This fixture that has a straight line to the sewer mainline pipe. It is also the largest drainpipe to the sewer in your home. Any problems with the main sewer pipe you would become aware of it here first. It is unusual to have a sewer mainline pipe clog and have the toilet working correctly. You can also check by flushing the toilet and if you see water backing up into the shower, it is another sign of a clog in the main sewer pipe. When the toilet is flushed, if the water is unable to go down the sewer pipe it will back up and come out at the lowest point. This is normally the drain in the shower.

Shower and tub

As mentioned, the shower and tub drains are at a lower level than other drains such as a sink drain. When water does not go down the sewer pipe, it comes back up at the lowest points.

Washing machine

When your washing machine starts to empty the water that is draining out and causes a back up in your shower, tub drain, or causes your toilet to overflow. Although this can be a sign of a sewer mainline pipe clog, it could also mean that you have a problem with your washing machine and not a clogged pipe. If you can still flush the toilet okay without any signs of a sewer backup then it is most likely a problem with the washing machine.

Another thing that you can check to see if there is sewer mainline pipe clog is to see if you have a main line clean out. If you know where it is or can find it, open it by pulling or unscrewing the cap. Check to see if there is any water or waste that is back up. Normally there should be no water coming up in this pipe but if you do this is confirmation of a sewer mainline pipe clog. If you are unsure what to do call a professional plumber.