Kitchen sink backing up into the other basin in Calgary, why?

When one basin backs up into the other, the shared drain line between the two sinks is partially or fully blocked somewhere between the P-trap and the point where that line meets the main stack. Water takes the path of least resistance, and if the drain is sluggish or stopped, it pushes back up through the other basin's opening.

What is actually happening under your sink

Both basins of a double kitchen sink share a single drain assembly that joins into one P-trap or a centre tee before heading into the wall. A grease, food particle or soap build-up anywhere in that shared section creates a partial dam. Running water in one basin raises the level in the shared pipe until it spills into the other. A fully blocked line will back both basins up at once.

The usual suspects are grease accumulation (cooking fats solidify in the pipe), food debris that bypassed the strainer, soap scum layered over time, or a combination of all three. If a garburator is on one side, ground food particles are a frequent contributor.

Before you call anyone, try this: remove the P-trap cleanout plug if there is one, or remove the P-trap itself with a bucket underneath. Clear any visible blockage. If the trap is clear, the clog is further down the drain arm or in the wall. A plunger on one basin while the other is sealed with a wet cloth can sometimes shift a partial blockage, but repeated chemical drain cleaner use is hard on older pipes, so tell any plumber you hire if you have used one.

If clearing the trap does not fix it, the blockage is in the horizontal drain arm running into the wall, or in the stack itself. That is where a plumber's snake or, for a stubborn clog, hydro-jetting becomes the right tool.

Typical Calgary cost for a professional drain clearing: a kitchen sink line runs roughly $150 to $300 for a standard snake; if the blockage is in the main line, expect around $400, and hydro-jetting a main line runs $400 to $800. A call-out or service fee of $50 to $150 on top of the labour rate is common, so ask about that upfront.

No permit is needed in Calgary to clear a drain blockage or to remove and reinstall a P-trap, as long as the piping itself is not being altered.

If the drain backs up repeatedly within a few months, ask the plumber to run a camera down the line. A camera inspection costs $200 to $600 and will show whether there is a partial collapse, a belly in the pipe, or root intrusion that snaking alone will not fix long-term. Agreeing to a sewer repair without seeing that footage first is one of the more expensive mistakes a homeowner can make.

When you get a quote, the line most likely to hide extra cost is the hourly rate after the first hour, so ask whether the price is fixed or whether it converts to an hourly charge once the job runs long.