Short answer
Kitchen drains clog with grease and food, bathroom drains with hair and soap. If several drains back up at once, or water rises in the tub when the toilet flushes, the blockage is in the main line.
One drain or all of them?
A single slow sink is usually a clog in that fixture's trap or branch line. Trouble in several places, especially the lowest drains in the house, points to the main line.
- Toilet gurgles when the tub drains
- Water backs up in a shower or floor drain when the washer empties
- Sewage smell from several drains
What causes main line clogs
Tree roots in older clay or cast iron pipe, grease buildup, wipes and other items that don't break down, and sagging sections where waste settles.
What a plumber does
They clear the line with a snake or hydro-jetting, then often run a camera to see the cause. See drain cleaning and sewer line repair.
Questions
Are 'flushable' wipes safe?
Many plumbers and sewer utilities advise against flushing them, since they don't break down like toilet paper.
How can I prevent kitchen clogs?
Wipe grease into the trash rather than rinsing it down, use a sink strainer and run plenty of water with the disposal.
Why does my toilet bubble or gurgle when the shower runs?
Gurgling indicates that the main drain or plumbing vent pipe is obstructed. As wastewater flows down the line, displaced air cannot vent properly, pulling air backward through toilet trap water.
Can tree roots really enter solid sewer pipes?
Yes. Roots enter through micro-fractures and loose joint mortar seeking moisture. Once inside, root hairballs expand rapidly, catching toilet paper and causing sudden blockages.
This guide is general information, not professional, legal or insurance advice. Follow your insurer's instructions and local codes, and put safety first.