Why Does the Same Drain Keep Backing Up?
Quick answer
A drain that keeps clogging usually has build-up further down the pipe that plungers and store-bought cleaners only partly clear. Common causes are grease in kitchen lines, hair and soap in bathrooms, and objects that shouldn't be flushed. If several drains back up at once, or your basement floor drain backs up when the washer empties, the problem is likely in your main sewer line and needs a professional.
This is the most important clue:
- One fixture keeps clogging (just the kitchen sink, or just the tub): the blockage is usually in that fixture's own drain line.
- Several fixtures are slow or backing up, especially on the lowest floor: the problem is likely in the main line that carries everything out of your house.
- Water comes up in the basement floor drain or tub when you flush or run the washer: that's a classic main line warning sign. Call a plumber soon.
Common causes of repeat clogs
- Grease and food in kitchen drains. Fats go down as liquid, then cool and harden on the pipe walls. Each clog catches more.
- Hair and soap scum in bathroom drains. Hair binds with soap residue and forms stubborn clumps.
- "Flushable" wipes and other items. Most don't break down like toilet paper and snag in pipes and the main line.
- The clog was only partly cleared. A plunger or chemical cleaner can punch a small hole through a blockage, leaving most of it in place to catch the next one.
- Pipe problems. Sagging sections, old cast iron with rough interiors, or poor slope let waste settle.
- Tree roots. In older neighbourhoods, roots can grow into the main sewer line through small cracks and joints.
- Venting issues. If drains gurgle or drain slowly, a blocked plumbing vent on the roof may be part of the problem.
What you can safely try
- Plunger: use a cup plunger for sinks and tubs and a flange plunger for toilets. Cover the overflow hole on sinks and tubs for better suction.
- Clean the stopper and trap: pull out and clean bathroom sink and tub stoppers, where hair collects. If you're comfortable, place a bucket under the sink and clean out the U-shaped trap.
- Hot water for kitchen drains: running hot water after washing dishes helps move grease along (never pour grease itself down the drain).
- Skip the chemical drain cleaners. They can damage pipes, especially older ones, rarely clear the whole blockage, and make the job more dangerous for whoever works on the drain next.
Prevent the next clog
- Wipe greasy pans with paper towel before washing, and put fats in the garbage
- Use hair catchers in showers and tubs
- Only flush toilet paper
- Use a sink strainer in the kitchen
How SS Plumbing & Heating handles it
We clear the blockage fully, not just enough to get water moving. More importantly, we look for why it keeps happening, whether that's grease build-up, a problem in the main line or a pipe issue, so you're not calling us back next month. Our augers reach up to 75 feet, and our drain camera lets us see inside the pipe to pinpoint the problem. You'll get a clear price before we start.
A Few Questions We Get a Lot
Why does my basement floor drain back up when I do laundry?
The washer sends a lot of water down at once. If the main line is partly blocked, that water has nowhere to go and comes back up the lowest drain, usually the floor drain. This needs a plumber.
Are chemical drain cleaners safe for my pipes?
We don't recommend them. They can damage older pipes and fittings and usually don't clear the full blockage.
How often should drains be professionally cleaned?
Most homes don't need routine cleaning. If a drain clogs more than once or twice a year, have it checked to find the underlying cause.
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Drain acting up again?
Tell us which drains are affected and what you're noticing, and we'll help you figure out the next step. Sewage backing up after hours? We offer 24/7 emergency service, with any after-hours charge quoted upfront.
Call or Text 780-995-4140 | Book Furnace Repair | Learn more about our drain cleaning →
About Steve
Steve St. Louis is a Red Seal Journeyman Plumber and Gasfitter (Class B) and the owner of SS Plumbing & Heating Ltd. Based in Sturgeon County, Steve and his team have served Edmonton and area since 2020, with 24/7 emergency service and a 5.0 rating from 450+ Google reviews.