Signs you have a main sewer line blockage

Individual drains clog constantly and it is a nuisance. A main sewer line blockage is a different category of problem, because everything in the house drains through it and when it fails the water comes back inside.

The signs, roughly in order of seriousness

1. 1More than one fixture draining slowly at the same time. A single slow sink is a sink. Two slow fixtures on different sides of the house is the line they share.
2. 2Gurgling in one fixture when you use another. Flush the toilet and listen at the tub. That sound is air being pulled through standing water because the line is partly blocked.
3. 3Water appearing where it should not. The washing machine empties and water rises in a shower or floor drain — that is the line backing up to the lowest opening it can find.
4. 4The lowest fixtures affected first. Basement and ground-floor drains go before upstairs ones, because gravity.
5. 5Sewage smell indoors or around the property, which means waste is sitting somewhere it is not moving through.

Outside signs people miss

• An unusually green, fast-growing strip of grass in a line across the yard — something is fertilising it
• A soft, wet or sunken patch over the run of the sewer line, in dry weather
• More rodent or insect activity than normal near the line
• A sewer smell in the yard, particularly after rain

What causes them here

In San Juan County the top three are tree roots, grease accumulation, and pipe age. The older neighbourhoods have clay-tile laterals with mortar joints, and mature cottonwoods and elms directly over them. Roots find the joints, get in, and then catch everything that passes.

What to do if you suspect it

1. 1Minimise water use immediately — every litre has to go somewhere
2. 2Do not use chemical drain cleaner. It will not clear a main line, and it makes the line hazardous for whoever opens it
3. 3Find your cleanout if you can, usually a capped pipe near the foundation or in the yard, and note where it is
4. 4Call. A main line blockage does not improve with time and the failure mode is sewage indoors