Has your kitchen sink ever started gurgling and bubbling while your washing machine is draining? This common plumbing problem is annoying, but luckily, it’s usually an easy fix. Here’s what causes it and how to stop it from happening.
What Causes the Gurgling
There are a few potential culprits behind a gurgling kitchen sink during washing machine drainage:
Clogged or Undersized Drain Pipe
The most likely cause is a partial clog or blockage in the drain pipe that connects your washing machine to the main sewer line. This shared drain pipe carries wastewater from both appliances. If it becomes clogged with food waste, grease buildup, soap scum, or other debris, it can impede the washing machine drainage and make your sink gurgle as a result.
An undersized drain pipe can produce the same effect. If the drain line is too narrow to handle the volume of wastewater from both the sink and washing machine simultaneously, it can back up and cause gurgling.
Improper Drainage Slope
For optimum drainage, sink and washing machine drain pipes need to slope downward at a grade of at least 1/4 inch per foot. If installed improperly without enough slope, drainage from the washing machine may flow slowly or back up, funneling water into the sink drain and causing gurgling noises.
Venting Issues
Plumbing drainage systems require proper venting to allow air in to break the vacuum seal. Without venting, suction can siphon water out of the sink trap and allow sewer gases to rise up the drain. This can manifest as gurgling sounds as air bubbles break through the water in the trap.
Shared Waste Stack
In some homes, the sink and washing machine drain lines connect to the same vertical waste stack before tying into the main house drain line. If improperly installed, this shared vertical drain pipe can let washing machine wastewater backflow into the sink drain, causing the gurgling noise.
How to Fix Gurgling Drains
Fortunately, fixing a gurgling kitchen sink caused by your washing machine is usually a pretty straightforward DIY project. Here are some tips:
- Clean the drain pipes – Use a plumber’s snake, drain auger, or Zip-It tool to remove any built-up gunk in the drain line. Start from the washing machine box then send the auger down toward the main drain.
- Check venting and slope – Inspect drain vent pipes for blockages. Measure slope using a level and adjust as needed. Minimum slope is 1/4 inch per foot.
- Upgrade to larger drain pipes – If drain is undersized, replace with wider diameter pipes to handle added drainage capacity.
- Install a backflow preventer – For a shared waste stack, add a backflow preventer valve to prevent washing machine water from flowing back into the sink drain.
- Reposition drain lines – Reroute pipes to separate the sink and washing machine drains. Join them as close to the main drain line as possible.
When to Call a Professional
DIY drain cleanings and adjustments may do the trick. But if you still have a persistently gurgling sink, it likely requires professional service:
- A plumber can snake the drain lines with larger, more powerful equipment. They can also visually inspect pipes with a sewer camera to identify any blockages or issues.
- For damaged, severely clogged, or improperly installed pipes, a plumber may need to replace sections of drain line.
- If the clog proves stubborn, the drain line may need hydrojetting, which uses highly pressurized water to clear tough blockages.
So don’t put up with a chronically gurgling sink! With some diligent DIY repairs or help from a professional plumber, you can silence this noisy nuisance.
