Sometimes our bathroom sink will drain so slowly (with the water running) that the water will fill it faster than it can drain.

However, after shutting the water off and letting it completely subside, it will typically drain properly the rest of the day and for the next several.

Then after a few days it will repeat its previous behavior.

Running Drano through the pipes has not seemed to have made a difference.

What could cause this behavior?

3 Answers 3

  • Remove the trap from the tailpiece of the wash bowl and see if it needs cleaning.
  • Check your main vent stack that goes through the roof for any obstructions. Verify that a bird has not made a nest there.
  • If the sink was not installed by a plumber and has always had this problem, an air vent pipe may not have been installed or was installed incorrectly.

While the tub and sink are empty and dry, pour a cup or so of baking soda down both drains. Use a skewer or a chopstick to get as much of it down the drains as possible. Then pour a liter or so of HOT vinegar into each drain.

Don't be surprised if enough hair to make a wig starts bubbling up.

Pull it out and toss it in the trash.

Use a hair screen over the drains for all future showers.

There is also an inexpensive plastic gizmo that can be used to drag hair and sludge from the pipe.


(I have no monetary interest in this product. I am just a satisfied user.)

Shampoos, conditioners and moisturizers love to get together and hang out. Regular (monthly) baking soda/vinegar treatments can keep your drains flowing.


I too had a similar problem: our cloakroom sink was always overflowing due to slow drainage. I tried everything, acid, rods, removing the pipes. It was a mystery and it was looking like we were going to have to reattach the pipe work elsewhere. As a last resort I bought a Blockblaster from a TV shopping channel not expecting much, but boy was I wrong. It uses CO2 gas like what you get in fizzy drink makers so it's very safe. I needed to cover the overflow, fill the sink with water and then cover with the Blockblaster sink attachment then push the button to blast out the gas. There was a bit of vapor (dry ice) and a smell of eggs! I ran the tap and the water flowed straight down the plug and continued to do this constantly. It has flowed ever since and that was over a year ago! We think there may have been sandy grit in the pipes that the rods couldn't clear and as the Blockblaster was so powerful it blasted it all away!

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