Most of the time, a washing machine shares a drain with a sink. This is because every house has the main drain that leads to the septic tank. However, there are instances when the washing machine will drain into the sink, not the main drain as it should be.
For the washing machine to drain into a sink, it means they’re connected before they reach the main drain in the house. So, if there’s a blockage after the sink but before the main drain, the washing machine will drain into the sink. This can also be a result of vent issues.
If your washing is draining into the sink and you’re looking for the causes and best solution, this guide will expound more on that.
Can Washing Machine and Bathroom Sink share a Drain?
A washing machine and bathroom sink can share a drain if the laundry room is next to the bathroom. This is when the plumbing connection and space are tight in the basement. In this case, you should fix a tee (plumbing fixture) to connect the sink’s drainpipe to the washing machine’s drain inlet.
However, you need to ensure that the standpipe is properly vented. Also, check the fixture count of the standpipe you’re to add to the existing bathroom drain. Let it not exceed the amount the pipes can handle.
How to Connect Your Washing Machine and Bathroom Sink to One Drain?
To enable your washing machine and bathroom sink to share a drain, do the following;
Fix the Tee
The first thing you need to do for the washing machine and bathroom sink to share a drain is fixed the sewer tee. Check the sewer pipe inlet near the washing machine and the bathroom sink. You should install one if there is no tee connection for the sink.
To achieve this, do;
- Disconnect the water supply to the sink and washing machine. The fixtures have two separate supply valves for cold and hot water. Use them to turn off the water supply.
- Then remove the washing machine from the socket.
- After that, divide the sewer line in half. If the pipe is metallic, use a rotary cutting tool with a metallic blade, while for a PVC, use a hacksaw. Then sand the rough edges after cutting the pipe.
- Then install the tee to the drainage pipe. To enable the tee to hold better, use hose clamps, rubber couplings, or primer, depending on its material. Also, ensure the tee points towards the sink’s drainpipe.
- Finally, attach the top of the tee to a straight drain pipe. Ensure it holds well by fixing it to the wall using a clamp or have it holding the nearby stud.
Connect the Drain from the Bathroom Sink and the Washing Machine
After successfully fixing the tee, you should work on connecting the two drains and the main drainage system in the house.
To do this, you should;
- Attach the washing machine’s drain hose to the top of the sewer pipe. Use a plastic tie to hold it into place.
- Then connect the p-trap and drain pipe and place them between the sewer and tailpiece. Doing this will enable you to know whether to cut the pipes further.
- After that, you should fix the sink drainpipe to the tee inlet. Use primer and PVC glue for PVC pipes, while the pipe thread compound will help stick the metallic drainpipe.
- Also, attach the p-trap between the tailpiece and drainpipe below the sink. Place couplings over the edges and use a wrench to tighten them further.
- You should afterward reconnect the water supply by turning the valves anticlockwise.
- Don’t also forget to reconnect the washing machine to the wall socket. Test if your washing machine and bathroom sink are sharing a drain without hitches.
What can Cause Water From Your Washing Machine to Back into Your Kitchen Sink?
Two major reasons can make your washing machine drain into the sink.
They include;
Vent Problems
If your washing machine and kitchen sink have separate vents that run through the walls and connect to the main vent stack, then here’s where the issue lies. It could be that there’s a blockage on the main stack. It could also be that leaves or dirt are on the vent blocking it.
The blockage will interfere with airflow affecting how water moves through the drain pipes. You will know this when there is a guggling sound from the sink drain as the washing machine drains.
You should clean the vent and the opening where the dirt comes through. Then test if the vent is working by pouring some water.
Wrong Size of Drain Pipes Causing Blockage
Another reason that will make your washing machine back on the sink is the wrong choice of pipes. Usually, the drain pipes used in the kitchen should be between 11/2 inches to 2 inches, and the washing machine drainpipes are 2 inches.
So, if you use smaller pipes, there would be issues. The kitchen sink is prone to experience blockage from the food particles that drain into the pipes and the grease from soap. Since the washing machine emits high water volume into the drainage system, a simple blockage will cause such issues. If it’s shared drainage, the problem can be frequent.
What to Consider When Sharing a Drain for Your Washing Machine and Sink?
If you want to share the drainage system for your washing machine and sink, consider;
- The size of the pipes; smaller pipes will cause clogging, while bigger pipes will not drain the water well.
- Venting; the drain pipes require adequate airflow to prevent blockage and guggling sounds.
- The angles of the pipes; you should also ensure the drain pipes are sloped to enable free water flow and prevent backing or blockage. The horizontal pipes need to be inclined by at least a quarter inch.
Bottom Line
If your washing machine is draining into the sink, there could be a blockage in the main drainage system. It can also result from poor ventilation and wrong pipe choice. You can also have your washing machine share a drain with the bathroom sink if the laundry room is next to the bathroom. If you decide to do this, ensure you fix a tee and connect the drains properly to avoid backing.
