A Slow Draining Sink is 100% Preventable & Easy Too. Do This!

A slow draining bathroom sink is caused by a partial clog due to accumulation of hair, soap scum and other bathroom products in the drainpipe and P-trap, restricting the flow of water.

It could also be caused by a clogged vent or even sink overflow which creates negative air pressure in the drainpipe.

To fix a slow draining bathroom sink, pull out hair from the drain with a hair removal tool. Blast hot water down the sink drain to flush out everything else. If that doesn’t work, remove and clean the sink P-trap. Plunging will also clear light clogs.

A slow draining bathroom sink that is not clogged is often caused by a blocked vent stack. Since air cannot flow out, pressure builds up in the drainpipe inhibiting the free flow of water from the sink. Sometimes it is as a result of a clogged drainpipe/sewer line or even a full septic tank.

A new bathroom sink that is draining slow is often caused by poor plumbing. Either the sink has no overflow or the P-trap is not installed the correct way. The high end of the trap should trap should be the one connected to the tail piece.

While some chemical drain cleaners will help unclog a slow draining sink, they will eat the rubber O-rings causing leaks. They also weaken the plumbing pipes and are especially not recommended if you are on a septic system.

Drano for instance will help fix a slow draining bathroom sink. Just squirt enough of it down the sink drain, wait for 15 minutes then run hot water to completely clear the drain.

How to Fix a Slow Draining Bathroom Sink

There are several methods you can use to fix a slow draining bathroom sink, some very easy and quick while other are a little harder and time consuming. This will however depend on the nature of your clog.

In this post I will first give you a brief summary of the solution and then later give you the long answer. Here is the short guide:

  • Remove Debris from the Drain Stopper: Open the sink’s pop-up stopper or remove the drain plug and clean it of any hair, soap scum, or debris that may be obstructing the flow of water.
  • Clear the Drain with a Plunger: Seal the sink overflow (the small hole located near the top of the sink) with a wet cloth. Use a sink plunger to create a strong seal over the drain opening. Apply up-and-down pressure on the plunger to dislodge clogs. Repeat as needed.
  • Use a Drain Snake or Zip-It Tool: Insert a drain snake or a plastic Zip-It tool into the drain to physically remove clogs that are deeper within the pipe. Gently pull out any debris.
  • Try a Chemical Drain Cleaner: Use a chemical drain cleaner if the clog persists. Follow the product’s instructions carefully and take necessary safety precautions, such as wearing gloves and eye protection.
  • Boiling Water and Baking Soda-Vinegar Solution: Pour boiling water down the drain to help dissolve grease and soap scum. Follow with a mixture of baking soda and vinegar to create a foaming reaction. Allow it to sit for a few minutes before rinsing with hot water.
  • Check the P-Trap: Place a bucket or towel under the P-trap (the curved pipe beneath the sink) to catch any water.Loosen and remove the P-trap to inspect for clogs or debris. Clean it thoroughly and reattach.
  • Ventilation Issues: Ensure that the sink’s vent system is not blocked, as poor ventilation can cause slow drainage. This may require professional assessment.
  • Professional Help: If none of the above solutions work or if you suspect a more significant plumbing issue, consult a professional plumber for a thorough inspection and repair.

And now the longer explanation:

1. Use Hot Water and Dish Soap

Hot water is very effective in dissolving soap scum and other products used in the bathrooms. The truth of the matter is that hair on its own does not clog the drain. It needs a sticky substance like soap to stick on the drain and P-trap.

By dissolving the soap scum, oils and other bathroom products, the hair will easily flow down the drain. It may sound counterproductive to use dish soap to unclog a sink where soap scum is major cause but liquid dish soap helps to lubricate the clog so that it flows out easily.

Here is how to unclog a bathroom sink with hot water and dish soap.

  • Drain the sink. If there is any water in the sink drain it out or wait for it to drain.
  • Pour ¼ cup of dish soap in the sink drain and wait for about 10 minutes. This will give it sufficient time to lubricate the clog. As you wait, boil 1-2 gallons of water.
  • Dump the hot water in the sink all at once.
  • The heat and weight of the hot water will break the clog and force it down the drain.
  • Depending on how badly the sink drain was clogged, you might have to do this one more time.

2. Use Baking Soda and Vinegar

Baking soda and vinegar are very effective in unclogging drains especially if you do not want to use harsh chemicals. A fizzing reaction occurs when you mix vinegar and baking soda and that is how clogs are broken down.

Sometimes people don’t get the results they are looking for after using baking soda and vinegar to unclog drains. This is often because they don’t know how to do it right.

This is how to unclog a slow draining bathroom sink using baking soda and vinegar:

  • Turn on the hot water. Let the hot water run for about 30 seconds. This will loosen the clog a little. Wait for the water to drain completely.
  • Pour ½ cup of baking soda down the sink drain.
  • Slowly pour vinegar down the drain. I insist you pour the vinegar slowly as it reacts very fast with baking soda. Let the solution sit for 15-30 minutes.
  • Blast hot water down the sink drain. Dump a gallon of hot water in the sink. This water will help wash down the loosely held hair strands and fully unclog the drain.

3. Plunge the Sink

A drain plunger is a fantastic tool to fix a slow draining sink. It works by creating a pressure differential, where the pressure acting on the clog from above is more than the one below it.

You have to be careful in your selection of plunger. There are 2 types of plungers, flat-bottomed plungers and bell-shaped plungers. Bell-shaped plungers are specifically designed for unclogging toilets.

For your slow draining sink you need a flat-bottomed plunger. One with a wooden handle might need gloves to avoid blisters.

Here is how to effectively unclog a bathroom sink with a plunger:

  • Plug off the overflow. The sinks overflow and the drain are connected. If you don’t plug it off, the pressure generated by the plunger will escape through it. Stuff a cloth in there.
  • Turn on the hot water faucet. What most people don’t understand is that to unclog a drain you need water. It is the water that will push hard against the clog forcing it to dislodge. You also need to ensure that the plunger cup is immersed in water to create a stronger siphon.
  • Where the water level in the sink is about the ¼ mark, place the plunger over the sink drain. The first plunge needs to be gentle to engage the plunger and then plunge aggressively before the water below the plunger drains.
  • After every few plunges, lift off the plunger to allow more water in the drain the plunge some more.

Plunging a slow draining sink is not as effective as a fully clogged sink. This is because after the water below the plunger drains, there will be nothing to generate the needed pressure to dislodge the clog.

4. Clean the Stopper

A bathroom sink stopper is not designed like other bathroom drain stoppers. It has a mechanism that extends inside the drainpipe that allows the stopper to be connected and controlled by the lift rod.

Due to that design, bathroom sink stoppers tend to catch a lot of hair, which is the number one cause for a slow draining bathroom sink. Removing and cleaning the stopper might be enough to restore your sink’s draining rate.

Removing a modern bathroom sink stopper is very easy. You just need to turn it counterclockwise to unscrew it and then simply lift it out. Most stoppers will however need you to get below the sink and disconnect it from there.

Here is how the bathroom sink stop mechanism works: The lift rod is connected to the pivot rod by the clevis rod. A clevis rod is the rod with holes that allows you to adjust the extent to which the pivot rod moves.

The pivot rod is in return connected to the stopper inside the sink drain. To remove the stopper, you need to first disconnect the pivot rod.

  • Disconnect the pivot rod and the clevis rod. Before doing that, use a marker to mark the specific hole that the pivot rod is connected to on the clevis rod. Once that is done remove the clevis clip and pull out the pivot rod from the clevis rod.
  • Loosen the pivot rod nut. Often this nut is made of plastic. Attempt to loosen it with your bare hand first before reaching out for the wrench. Pull out the pivot rod.
  • Once the pivot rod is out, the sink stopper is free. All you have to do is lift it out. It helps to have rubber gloves on as the stopper might look really gross.
  • Remove the hair with paper towel and clean the stopper thoroughly.
  • Dump hot water down the sink drain and check if its draining has improved.

5. Snake the Sink Drain


If cleaning the bathroom sink stopper was not sufficient to restore your sink’s draining rate, snaking it might help. The best thing is that you don’t need to use the usual plumber’s snake.

A drain hair removal tool is a flexible plastic tool that is hooked along its edges. You just need to feed it down the sink drain while rotating/turning it. This is the same tool you would normally use to remove hair form a slow draining bathtub or shower drain.

You might have to force the tool to go through the P-trap. The best thing about this tool is that unlike the ordinary drain snake it cannot damage the pipes.

To fully unclog the sink drain, put the tool in and out of the drain several times until you can’t see any strand of hair when you pull it out. Connect the stopper and pivot rod back.

Turn on the hot water faucet for about 30 seconds to wash down any debris loosely attached to the drain. You cannot do this before connecting back the stopper, lest water will pour out through the pivot rod opening.

If you do not have this tool, grab a wire coat hanger (or just any strong wire) and straighten it. Make a small hook on one end of the wire and push it down the sink drain. Fish out as much gunk as possible.

You can still use the usual drain snake although it is one of my least favorite methods. This drain uses a spring-like and hooked head which if you are not careful will make a hole if you have plastic pipes. That will be an expensive repair.

The best method to unclog stubborn sink drains is to remove the P-trap and clean it.

6. Remove and Clean the P-Trap

The P-trap is the curved part of your sink’s drainpipe. It looks like a U or inverted P. Every fixture in your house with a drain has a trap.

A drain trap serves 2 purposes:

  • It traps potential drain clogs preventing them from clogging the drainpipe further away.
  • It holds a constant amount of water. This water creates a seal preventing sewer gas smells from coming up into your bathroom. Any time you have a sewer gas smell in your bathroom it means one of the drain traps is usually empty.

Whenever you have a slow draining bathroom sink, it means you have a partial clog in the drainpipe. Most of the time the clog is usually in the P-trap.

Here is how to remove and clean a bathroom sink p-trap:

  • Clear the space. If you use the space under the bathroom sink to store stuff remove them.
  • Put a bucket under the P-trap. You do not want stinky water to drip on the floor.
  • Disconnect the P-trap. As you can see on the trap, one connection is usually higher than the other. I like to start with the lower connection so that water trapped in the drainpipe can flow out via gravity. Often the connections are usually hand tight. Attempt to loosen them with your bare hands before reaching out for the wrench. Immediately you loosen the first connection, don’t remove it fully until all the water has dripped inside the bucket.
  • Disconnect the second connection.
  • Inspect the inside of the P-trap. I am pretty sure you will find a lot of gross gunk. Inspect the drainpipe as well, in case the clog had extended there.
  • Clean the P-trap. Remove as much gunk as you can from the P-trap before dropping it it in separate container for thorough cleaning.
  • Once the P-trap is clean connect it back to the drainpipe.
  • Turn on the water and check out the new rate of draining. Don’t forget to check for leaks in the drain trap. If any tighten the trap a little more.

If you have a new bathroom sink that is draining slowly check out this post.

7. Clean the Sink Overflow

A sink’s overflow is the opening at the top of the sink. It has 2 major functions.

  • It prevents flooding. When the level of water in the sink is too high, the excess water flows back to the drainpipe via the overflow.
  • It lets in air inside the drainpipe, allowing the sink to drain faster. If the overflow line is clogged, air will not flow into the drainpipe and hence a slow draining sink.

Cleaning a sink’s overflow is easy. Just grab the drain hair clog removal tool and stick it inside the overflow. Probe the overflow several times to remove out all the gunk.

If you to go a little further, stick a funnel in the overflow and pour ¼ cup of baking soda followed by the same amount of vinegar. Wait for 15 minutes then blast hot water through it.

8. Unclog the Vent Stack

If you have a bathroom sink that is draining slowly but is not clogged, the vent is usually the culprit.

The vent stuck is the vertical pipe that runs from your main house drainpipe through the roof. It removes sewer gases from the drainpipe while at the same time allowing air to circulate freely inside the pipes.

In order for the drains in your house to drain optimally, there must be air in the drainpipe. When the vent is clogged, there is no more circulation of air meaning the drains’ will start to drain slowly and in the case of a toilet have a weak flush.

Signs of a clogged vent stack include:

  • Toilet bubbling when flushed.
  • Bathroom sink and tub drains slowly
  • Bathtub/shower drain gurgling when the toilet is flushed.
  • All sinks draining slowly.
  • Bathroom sink gurgling when the toilet is flushed or tub drains.

If any of these signs is present in your bathroom, take a ladder and climb to the roof of your house armed with a garden hose.

  • Check if there is trash at the top of the vent that you can easily remove with your hands. These includes dry leaves, dead rodents/birds and even snow.
  • Stick the garden hose down the vent to check for blockages. If you feel any, probe it repeatedly with the hose. Have someone turn on the water to the hose. The weight of the water will be enough to dislodge the clog.
  • If the clog does not bulge, upgrade to a better tool. The drain snake. Snake the vent until water can flow through it freely.

Other reasons your bathroom sink could be draining slowly can be as a result of a full septic tank or the main drainpipe or sewer pipe are clogged. This problems will however also affect the other fixtures like the kitchen sink, bathtub/shower and washing machine.

In case you suspect that the problem is with the drainpipe, sewer line or septic tank, you should call in a professional plumber. Some things are better left to experts.

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