A double kitchen sink makes food preparation and after-meal cleanup more manageable. With a double kitchen sink, you can do your meal prep in one sink and stack dirty dishes in the other. A double bowl sink also means your kitchen garbage disposal is always accessible.
But Sage Property Management warns that just like a single-bowl kitchen sink, double-bowl kitchen sinks can also have problems. A common issue with both sink types is they can get clogged. Kitchen sinks handle a lot of food scraps, so it is not surprising that they sometimes get blocked.
When clogs happen in a double kitchen sink, they can show up on one or both sides of the sink. You may also encounter the strange phenomenon where one side of the sink backs up into the other. Why does one side of a double sink back up into the other side, and how do you solve it?
Why your double sink backs up to the other side
The cause of this problem can be simple or complicated. There are five possible reasons why one side of your double sink backs up to the other.
The sink drain is clogged
If your double kitchen sink is backing up to one side, the first thing to do is check for clogs in the drain. If a drainpipe is blocked, any water you pour into the drain will simply collect in the pipe until it overflows and backs up into one bowl of the double sink. If you think your drain is blocked, try to unclog it with a plunger.
Clogged garbage disposal
A clogged or jammed garbage disposal unit can also affect the water flow from your double kitchen sink. To check if the problem is from the garbage disposal, unplug the unit and run water into both sides of the sink separately. If the sinks drain properly, you may have a clogged or damaged garbage disposal.
Blocked P-Trap
The P-trap can be found under the sink; look for a P-shaped pipe below your sink. Its purpose is to keep bad-smelling sewer gasses out of your home. Sometimes, this pipe can become clogged with grease and food particles. If this happens, water will not flow freely from your kitchen sink. To clean a blocked P-trap you must uncouple it and clear its contents.
A clog in the vent stack
A less common but highly-possible reason why one side of your double kitchen sink backs up into the other side is that your vent stack is clogged. A vent stack is a set of vertical pipes that let air into the plumbing system so water can flow freely. If the air stack is clogged, areas of low air pressure will form inside drainpipes as water flows through them. This can result in backups.
A clogged sewer line
The final and worst reason a double kitchen sink may be backing up on one side is a clogged sewer line. If the sewer line is clogged, water entering the sink drain will have nowhere to go except to flow upwards through a nearby opening. Although a clogged sewer line can cause backups in your kitchen sink, it is the least likely cause of the problem.
What to do when your double sink backs up on one side
To determine the exact reason your sink is acting up, you must eliminate each potential cause of the problem, beginning with the easiest one. You do this by systematically applying the listed steps:
Use a plunger
If you think the sink is backing up because the sink drain is clogged, try unclogging the drain with a plunger. If unsure which sink hole is clogged, use the plunger on both. When plunging a sink hole, ensure the other sink hole is covered or plugged in.
Use vinegar and baking soda
Pour a cup of baking soda into the drain opening of each sink, wait a few minutes and then pour a cup of vinegar into each opening. Let the mixture sit inside the drain for five minutes. Pour hot water into the drain to clear it.
Use salt and boiling water
You can use salt and boiling water if you don’t have vinegar at home. Firstly, ensure there is no standing water inside the sink. Pour half a cup of salt into each sink opening and follow it with boiling water.
Clean the P-trap
If the above steps don’t work, you may need to remove the p-trap, to clean it. Removing a p-trap is easy; you just need a screwdriver and some patience. Have a bucket handy to catch any mess inside the trap.
Call your plumber
Lastly, if you have tried everything and the problem will not go away, the only option is to call a professional plumber. The plumber will tell you if the problem is from your garbage disposal, vent stack or other causes. A good plumber will also tell you how to avoid the issue in the future.