Basement Sink Backing Up – What To Do?

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A sink is an essential fixture if you have a basement bathroom or laundry room. If the sink backs up, you might not be able to use it. The water can come from the toilet, bathtub, or washing machine. To help you solve the problem, we have researched what you should do when the basement sink is backing up.

For a basement sink that is backing up, follow the steps below:

  1. Determine the location of the blockage of water.
  2. Clean the strainer of your sink and unclog the trap with a plumbing snake or auger.
  3. If you use a plunger, close the sink stoppers and overflow holes.
  4. Use a suction tool to get the air out of the drain P-trap for blocked vents.

It will help to find out where the plumbing lines connect to your sink. Regular maintenance of the pipes prevents frequent water backflow. If you don't have prior experience with plumbing, you can ask a professional to do the work for you or read further to avoid the basement sink backing up.

A basement sink with gray cabinets with white painted walls and recessed lighting, Basement Sink Backing Up - What To Do?

What Causes The Basement Sink To Back Up?

A basement sink backing up happens when your sink gurgles or the water comes back after draining. Before you can solve the issue, the first thing to figure out is the reason for the water backing up in the basement sink.

A gorgeous kitchen basement with blue colored backsplash, wooden cabinets and glass walled cupboards

The possible causes include issues with the plumbing line connections and vent arrangement.

1. Sink Plumbing Connections

The sink is not the only fixture that needs water inside your basement.

A sink will back up if there is congestion in the shared water pipes. You might have a basement bathroom with a toilet and bathtub that shares a plumbing connection with the sink. The washing machine can cause backing up while draining if you have a laundry room.

The sink can be the victim of frequent water backing up if it is the lowest fixture inside the basement. In that case, it is easier for sewer water to escape and stand by in the sink.

2. Vent System Arrangement

Another reason is the distance of the toilet from a stack vent. You need to install a separate vent if the toilet is 10 feet away from the stack. If you want to avoid the problems, the vent and sink drain should be in a straight-line connection.

After considering the facts, you can fix the issue on your own.

What To Do When The Basement Sink Backs Up?

There are several ways to tackle a basement sink backing up. You can select the course of action based on the severity and source of the water backflow.

Before proceeding, remember that you must never use chemicals to clear the clogging. If you do, you might cause cracks in the pipes. The damage will cost you more in the long run if you do.

Learn how you can solve the issue for the two scenarios below.

A. Clogged Sink

You can try unclogging the sink with a simple process as follows:

  1. Take out the sink stopper and the strainer inlet to remove any debris. Be careful when pulling out these parts to avoid damage.
  2. Use a plumber's snake or auger to unclog the sink trap.
  3. If there is still a backflow, you will need to detach the trap underneath. Prepare a bucket below the trap to catch water and other gunk.
  4. You can use an electric snake or a scraper to remove the objects clogging the trap.
  5. Fasten the trap back in its position.
  6. If the problem is in the drain waste vent, use an air suction plumbing tool in the P-trap to unblock it.

B. Basement Fixtures Back Flow

If the toilet, washing machine, and other fixtures are causing the backing up, these instructions might help:

  1. Close the stoppers and overflow holes of your sink.
  2. Unclog the drain if the water comes from the toilet line with a plunger.
  3. If the plunger fails, insert an auger to clean out the waste line.
  4. If the washing machine drain causes the backflow, fill the sink with water before plunging it.

Can A Washing Machine Back Up The Basement Sink?

A gorgeous kitchen basement with blue colored backsplash, wooden cabinets and glass walled cupboards

Your washing machine can cause the back up of one or any of your basement sinks after the drain cycle. If you notice that the water in the sink remains, there could be a large volume of water drained by the washing machine. The reasons can be a clogged drain hose, faulty drain pump, or drive belt.

To fix the issue, turn off the machine first. An easy solution is to use a drain snake to unclog the drain pipe. You can also use the clean-out fitting behind the machine.

If the drain pump is defective, you should make a replacement. Contact a washing machine repair expert for other drive belt and lid switch issues.

Does A Basement Utility Sink Need To Be Vented?

Adding vents to your utility sink helps in the free flow of water through the plumbing lines. Most local residential codes require a dedicated vent to the sump box of the sink. The vents help equalize the pressure out the drain pipe. In this way, you prevent the gurgling sounds when draining the sink.

You can either use a traditional vent system or an Air Admittance Valve (AAV). For the traditional approach, it can be challenging to reroute the air through pipes to an external vent. The air can pass through the plumbing system when wastewater discharges from the sink with an AAV.

Can I Drain A Utility Sink To The Basement Floor Drain?

A basement drain is an integral part of the plumbing system. The drain connects to the sewer system, a sump pit, or an ejector pump. It is crucial to connect the drain of the utility sink. With the proper placement, you can quickly get rid of wastewater from the basement.

For a utility sink, the drain should connect to the sewer system. If the drain connects to the floor drain, this helps minimize the foul odor inside the basement. It would be best to keep the trap dry, and the plug-out should stay in place.

However, you can also encounter backflow with the connection. The clogging forces the sewage water up through the drain. Avoid the backflow by installing a backflow valve.

Check out a related post, How To Unclog A Basement Drain.

If your basement has no floor drains, try out any of these ideas:

  • Install an above-floor water pump on the basement floor. It is enough to pump out water from the sink drainage pipes.
  • Add exterior drain lines below the floor. This method is possible if you have a walkout basement because you need to remove a part of the wall. Assess the route if the drain connects to a wastewater line. Otherwise, you cannot do this option.
  • You can add a sump pump with an ejector pump. Select this method if you have a basement bathroom.

In Closing

A basement sink with gray cabinets with white painted walls and recessed lighting

A basement sink backing up is a fuss. The water can come from the washing machine and other fixtures in the basement with shared plumbing connections. A large volume of water can back up the sink if waste and other debris are clogging the pipes.

You must add vents to the sink to divert the water from the basement and ward off foul smells. Also, it will help if you connect the sink drain to the basement floor drain. If you avoid the water backflow in your sink, you can keep your basement dry and functional.

Read more about basements from these posts:

What Is A Basement Bathroom Rough-In? [And What Does It Look Like?]

How To Get Rid Of Sewer Smell In Basement Bathroom

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